White Light from Dual Intramolecular Charge-Transfer Emission in a Silylene-Bridged Styrylcarbazole and Pyrene DyadClick to copy article linkArticle link copied!
- Malgorzata Bayda-Smykaj*Malgorzata Bayda-Smykaj*Email: [email protected]Faculty of Chemistry, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 8, 61-614 Poznan, PolandCenter for Advanced Technology, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 10, 61-614 Poznan, PolandMore by Malgorzata Bayda-Smykaj
- Karolina RachutaKarolina RachutaFaculty of Chemistry, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 8, 61-614 Poznan, PolandMore by Karolina Rachuta
- Gordon L. HugGordon L. HugRadiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, United StatesMore by Gordon L. Hug
- Mariusz MajchrzakMariusz MajchrzakFaculty of Chemistry, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 8, 61-614 Poznan, PolandMore by Mariusz Majchrzak
- Bronislaw MarciniakBronislaw MarciniakFaculty of Chemistry, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 8, 61-614 Poznan, PolandCenter for Advanced Technology, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 10, 61-614 Poznan, PolandMore by Bronislaw Marciniak
Abstract
Styrylcarbazole linked to pyrene by a dimethylsilyl bridge was synthesized in the search for new charge-transfer active materials for LED applications. In the course of a photophysical study, it turned out that such a donor-bridge-acceptor compound displayed three completely different types of emission depending on solvent polarity. The most attractive emission properties were found in acetonitrile in which two broad emission bands were observed. The resolved mechanism of the excited-state processes in acetonitrile was supported by singular value decomposition with self-modeling treatment of time-resolved emission spectra (ns-TCSPC). The data analysis revealed that there were two excited-state processes, that is, charge transfer within styrylcarbazole and electron transfer from styrylcarbazole to pyrene through a silylene bridge that was responsible for a broad dual emission. The general idea of designing compounds that display emission from more than one excited state covering a wide range of the visible spectrum can be a powerful tool in designing new white-light-emitting materials.
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You are free to share(copy and redistribute) this article in any medium or format and to adapt(remix, transform, and build upon) the material for any purpose, even commercially within the parameters below:
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1. Introduction
Figure 1
Figure 1. White-light emission of compound 1 in ACN.
Chart 1
2. Experimental Section
2.1. General Methods
2.2. Nanosecond Time-Resolved Emission Spectroscopy
3. Results and Discussion
3.1. Color-Tuned Emission in Silylene-Bridged Compounds
Figure 2
Figure 2. Absorption spectra of compounds 1, 1a, and 1b in ACN.
3.2. On the Way to the White Light
Figure 3
Figure 3. Normalized fluorescence spectra (top panel) and energy diagrams (bottom panel) of compounds 1 (red line), 1a (light gray line), and 1b (dark gray line) in hexane (a,a1), DCM (b,b1), and ACN (c,c1). The colors of the energy diagrams correspond to colors of the spectral contours presented in the top panel.
3.2.1. Emission in Hexane (Local Excited (LE) State Emission from Pyrene)
3.2.2. Emission in DCM (CT1 Emission)
3.2.3. Emission in Acetonitrile (CT1 + CT2)
Figure 4
Figure 4. Time-resolved fluorescence spectra of compound 1 in ACN (λexc = 330 nm).
Figure 5
Figure 5. Resolved fluorescence spectra of pure CT1 and CT2 states obtained from SVD-SM and experimental calculations and steady-state fluorescence spectrum of 1b (a); combination coefficients (α, β, γ) of the normalized emission spectra presented as points in a 3D vector space spanned by the three most significant eigenvectors of the covariance matrix (b). The colors of the three spheres in (b) correspond to colors of the spectral contours in (a). The corners of the triangle correspond to the spectra of the pure components.
Figure 6
Figure 6. Fluorescence decays of compound 1 in ACN, λem = 420 and 560 nm and λexc = 330 nm.
Scheme 1
a(LE = emission from the local excited state; ET = energy transfer; HT = hole transfer; e̅= electron transfer; and CT1, CT2 = charge-transfer excited states).
4. Conclusions
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpcc.1c00990.
Synthesis procedures and methods used, calculated ΔGel and ΔGHT, absorption and emission properties (λAbs, max, λf, max, τs, and Φf), and kinetic equations derived for CT1 and CT2 (PDF)
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Acknowledgments
This work was supported by the Faculty of Chemistry, Adam Mickiewicz University, Poznan, Poland and the National Science Centre (grant no. 2017/25/N/ST4/00299). The document number NDRL-5308 from the Notre Dame Radiation Laboratory is supported by the US Department of Energy Office of Science, Office of Basic Energy Science, under award number DE-FC02-04ER15533.
References
This article references 42 other publications.
- 1Bayda-Smykaj, M.; Burdzinski, G.; Ludwiczak, M.; Hug, G. L.; Marciniak, B. Early Events in the Photoinduced Electron Transfer between Carbazole and Divinylbenzene in a Silylene-Bridged Donor-Acceptor Compound. J. Phys. Chem. C 2020, 124, 19522– 19529, DOI: 10.1021/acs.jpcc.0c07531Google Scholar1https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhs1aqsL%252FI&md5=d48bfaf37b44f80b1f12cb39e5c0cb7fEarly Events in the Photoinduced Electron Transfer between Carbazole and Divinylbenzene in a Silylene-Bridged Donor-Acceptor CompoundBayda-Smykaj, Malgorzata; Burdzinski, Gotard; Ludwiczak, Monika; Hug, Gordon L.; Marciniak, BronislawJournal of Physical Chemistry C (2020), 124 (36), 19522-19529CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Meeting the challenge of designing new light-emitting materials, we synthesized the compd. N-isopropylcarbazole (CBL)-SiMe2-divinylbenzene (DVB), which represents the general idea of building attractive emitters by stitching together simple, well-known block elements. Following this strategy, an extraordinary emission emerges from photoinduced intramol. processes between silylene-bridged adjacent chromophores, e.g., intramol. energy and/or electron transfer (PET). The reported compd. displays an attractive blue emission that occurs no matter which of the linked chromophores is excited (i.e., regardless of the excitation wavelength in the range 240-360 nm). Excitation of CBL leads directly to intramol. charge transfer (ICT) state formation within 35 ps, whereas excitation of DVB results in "pumping" the CBL excited state via 300 fs energy transfer. In the latter case, DVB acts as an intramol. photosensitizer of the ICT precursor. Both mechanisms, proceeding via ultrafast processes, are confirmed by femtosecond transient absorption expts. performed on the investigated bichromophoric compd. and its individual Si-contg. chromophores in acetonitrile soln. Anal. of the transient absorption bands allowed us to characterize the ICT excited state as a radical ion pair of carbazole radical cation and divinylbenzene radical anion linked by a silylene bridge.
- 2Fakis, M.; Beckwith, J. S.; Seintis, K.; Martinou, E.; Nançoz, C.; Karakostas, N.; Petsalakis, I.; Pistolis, G.; Vauthey, E. Energy Transfer and Charge Separation Dynamics in Photoexcited Pyrene-Bodipy Molecular Dyads. Phys. Chem. Chem. Phys. 2018, 20, 837– 849, DOI: 10.1039/C7CP06914FGoogle Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFWgtbnF&md5=be06938f856ead74b5620e365a346ef5Energy transfer and charge separation dynamics in photoexcited pyrene-bodipy molecular dyadsFakis, M.; Beckwith, J. S.; Seintis, K.; Martinou, E.; Nancoz, C.; Karakostas, N.; Petsalakis, I.; Pistolis, G.; Vauthey, E.Physical Chemistry Chemical Physics (2018), 20 (2), 837-849CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)The photophys. properties of two pyrene-bodipy mol. dyads, composed of a phenyl-pyrene (Py-Ph) linked to the meso position of a bodipy (BD) mol. with either H-atoms (BD1) or Et groups (BD2) at the 2,6 positions, are investigated by stationary, nanosecond and femtosecond spectroscopy. The properties of these dyads (Py-Ph-BD1 and Py-Ph-BD2) are compared to those of their constituent chromophores in two solvents namely 1,2-dichloroethane (DCE) and acetonitrile (ACN). Stationary spectroscopy reveals a weak coupling among the subunits in both dyads. Excitation of the pyrene (Py) subunit leads to emission that is totally governed by the BD subunits in both dyads pointing to excitation energy transfer (EET) from the Py to BD chromophore. Femtosecond fluorescence and transient absorption spectroscopy reveal that EET takes place within 0.3-0.5 ps and is mostly independent of the solvent and the type of the BD subunit. The EET lifetime is in reasonable agreement with that predicted by Forster theory. After EET has taken place, Py-Ph-BD1 in DCE and Py-Ph-BD2 in both solvents decay mainly radiatively to the ground state with 3.5-5.0 ns lifetimes which are similar to those of the individual BD chromophores. However, the excited state of Py-Ph-BD1 in ACN is quenched having a lifetime of 1 ns. This points to the opening of an addnl. non-radiative channel of the excited state of Py-Ph-BD1 in this solvent, most probably charge sepn. (CS). Target anal. of the TA spectra has shown that the CS follows inverted kinetics and is substantially slower than the recombination of the charge-sepd. state. Occurrence of CS with Py-Ph-BD1 in ACN is also supported by energetic considerations. The above results indicate that only a small change in the structure of the BD units incorporated in the dyads significantly affects the excited state dynamics leading either to a dyad with long lifetime and high fluorescence quantum yield or to a dyad with ability to undergo CS.
- 3Cho, J.; Park, J. H.; Kim, J. K.; Schubert, E. F. White Light-Emitting Diodes: History, Progress, and Future. Laser Photonics Rev. 2017, 11, 1600147 DOI: 10.1002/lpor.201600147Google ScholarThere is no corresponding record for this reference.
- 4Paik, K. L.; Baek, N. S.; Kim, H. K.; Lee, J.-H.; Lee, Y. White Light-Emitting Diodes from Novel Silicon-Based Copolymers Containing Both Electron-Transport Oxadiazole and Hole-Transport Carbazole Moieties in the Main Chain. Macromolecules 2002, 35, 6782– 6791, DOI: 10.1021/ma020406rGoogle Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XlslKisrw%253D&md5=11db643629fe5603cb24ec935a2ba403White Light-Emitting Diodes from Novel Silicon-Based Copolymers Containing Both Electron-Transport Oxadiazole and Hole-Transport Carbazole Moieties in the Main ChainPaik, Kyung Lim; Baek, Nam Seob; Kim, Hwan Kyu; Lee, Ji-Hoon; Lee, YoungilMacromolecules (2002), 35 (18), 6782-6791CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)Si-based alternating copolymers contg. both electron-transport oxadiazole and hole-transport carbazole moieties in the main chain (SiHMOXD/Cz 10-01) were synthesized by the Heck coupling reaction. The resulting polymers exhibit a strong UV-visible absorption band at 345-356 nm in CHCl3 soln. and in film state. Their PL spectra show a max. band around 435-485 nm in the blue region. The light-emitting diodes of Al (200 nm)/Ca (50 nm)/EL polymer (80 nm)/PEDOT (50 nm)/ITO were successfully fabricated. And, J-V curves show a turn-on voltage of 6-7 V. Their EL properties depend strongly on both the applied voltage and the loading amt. of hole-transport carbazole moieties in the present copolymers. With the applied voltage, these emissive EL bands were red shifted from blue region to red region. Also, the intensity of a blue EL band at the relatively high operating voltages increases with the loading amt. of carbazole units. The LED device with the copolymer of SiHMOXD/Cz 19 exhibits the almost same intensity of two bands, like two crests, giving a strong white color. The blue EL color comes from the carbazole units in these Si-based copolymers. The latter red EL color comes from a specific charge complex with oxadiazole (and carbazole moieties). The new red band is exhibited only in EL but not in PL spectra. The EL device based on SiHMOXD/Cz 19 has a luminescence efficiency of 0.052 lm/W and a power efficiency of 0.13 cd/A at an applied voltage of 9 V And, the max. luminance of the white emissive color was 6.04 cd/m2 at an applied voltage of 17 V. From the photophys. studies, a specific intramol. charge complex is proposed.
- 5Chen, Z.-K.; Huang, W.; Wang, L.-H.; Kang, E.-T.; Chen, B. J.; Lee, C. S.; Lee, S. T. A Family of Electroluminescent Silyl-Substituted Poly(p-Phenylenevinylene)s; Synthesis, Characterization, and Structure-Property Relationships. Macromolecules 2000, 33, 9015– 9025, DOI: 10.1021/ma0005670Google Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXns1Ois7s%253D&md5=d28fdbbda94af133ed93be71eb733f69A Family of Electroluminescent Silyl-Substituted Poly(p-phenylenevinylene)s: Synthesis, Characterization, and Structure-Property RelationshipsChen, Z.-K.; Huang, W.; Wang, L.-H.; Kang, E.-T.; Chen, B. J.; Lee, C. S.; Lee, S. T.Macromolecules (2000), 33 (24), 9015-9025CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)A series of intense photoluminescent (PL) polymers contg. silyl groups with chain length from C1 to C18 was synthesized through polycondensation reaction. The silyl groups in the conjugated polymer provide for improved processability, amorphous morphol., good film-forming ability, and sharp emission. Increasing the side chain length resulted in a slight decrease of thermal stability while increasing the mol. wt. The UV-vis absorption and PL emission spectra of the polymers are quite similar. A cyclic voltammetry (CV) study of the polymers reveals that the side chain length plays an important role in the redox behavior of the polymers. The short side chain polymers possess better reproducibility of CV scans and higher peak currents, which implies that the chem./elec. stability and charge injection and/or transport are more efficient than those for long side chain polymers. Test devices were fabricated from poly[2,5-bis(decyldimethylsilyl)-1,4-phenylene vinylene] (DS-PPV) with the configuration of ITO/DS-PPV/Mg:Ag and ITO/PEDOT:PSS/DS-PPV/Mg:Ag. Measurements indicate that hole injection is the detg. factor in charge transport. Addn. of a hole injection layer can improve the current efficiency and power efficiency by about 7 times and lower the turn-on voltage from 7.5 to 4.0 V for the two types of devices.
- 6Cho, Y.-J.; Lee, A.-R.; Kim, S.-Y.; Cho, M.; Han, W.-S.; Son, H.-J.; Cho, D. W.; Kang, S. O. The Influence of π-Conjugation on Competitive Pathways: Charge Transfer or Electron Transfer in New D−π–A and D−π–Si−π–A Dyads. Phys. Chem. Chem. Phys. 2016, 18, 22921– 22928, DOI: 10.1039/C6CP03259AGoogle Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1egtrjK&md5=810bc1e2a03becc7e8162aa5124333c2The influence of π-conjugation on competitive pathways: charge transfer or electron transfer in new D-π-A and D-π-Si-π-A dyadsCho, Yang-Jin; Lee, Ah-Rang; Kim, So-Yoen; Cho, Minji; Han, Won-Sik; Son, Ho-Jin; Cho, Dae Won; Kang, Sang OokPhysical Chemistry Chemical Physics (2016), 18 (33), 22921-22928CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)In order to elucidate the influence of π-conjugation on photoinduced electron transfer (PET) and intramol. charge transfer processes, donor-π-acceptor dyads (D-π-A (1) and D-π-Si-π-A (2)) were newly synthesized. In these dyads, carbazole and triazine moieties acted as the electron donor and acceptor, resp. The fluorescence of dyad 1 red-shifted as the solvent polarity was increased. The electron charge distribution of the excited state of dyad 1 was delocalized in the acceptor moiety, forming the charge transfer Dδ+-π-Aδ- dyad in the excited state. In the excited state of dyad 1, the π-conjugation acted as the linker for charge transfer between the donor and acceptor moieties. A large dipole moment change (Δμ = 45.6 D) between the ground and excited states was detd. using the Lippert-Mataga plot. Furthermore, the fluorescence of dyad 1 was obsd. upon two-photon excitation. In contrast, dyad 2, in which the π-conjugation is disconnected by a Si-atom in the linker, displayed weak dual-emission: a short-wavelength emission at around 350 nm arising from the monomeric species and a long-wavelength one assigned to the emission from an intramol. exciplex between the donor and acceptor moieties. The weak emission of dyad 2 indicates that the D+̇ -π-Si-π-A-̇ species was generated through a PET process in the excited state. The cationic radical species of the carbazole and the anionic radical species of the triazine, which show transient absorption (TA) bands at around 780 and 530 nm, resp., were characterized using the femtosecond TA method.
- 7Kim, S.-Y.; Cho, Y.-J.; Lee, A.-R.; Son, H.-J.; Han, W.-S.; Cho, D. W.; Kang, S. O. Influence of π-Conjugation Structural Changes on Intramolecular Charge Transfer and Photoinduced Electron Transfer in Donor−π–Acceptor Dyads. Phys. Chem. Chem. Phys. 2017, 19, 426– 435, DOI: 10.1039/C6CP06566JGoogle Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvFCisrzE&md5=f30ef6d9ea5ff4b43ddd606c055d0c5cInfluence of π-conjugation structural changes on intramolecular charge transfer and photoinduced electron transfer in donor-π-acceptor dyadsKim, So-Yoen; Cho, Yang-Jin; Lee, Ah-Rang; Son, Ho-jin; Han, Won-Sik; Cho, Dae Won; Kang, Sang OokPhysical Chemistry Chemical Physics (2017), 19 (1), 426-435CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)The influence of π-conjugation structural changes on photoinduced electron transfer (PET) and intramol. charge transfer (ICT) processes in π-conjugated donor (D)-acceptor (A) dyads (D-π-A) was investigated. Three types of D-π-A dyads were prepd. through the modification of the structure of their π-conjugated linker, including D-π-A (1) and D-πtw-A (2) having a twisted π-conjugation, and D-π-Si-π-A (3) with a π-conjugation severed by a Si-atom. In these dyads, carbazole (Cz) and oxadiazole (Oz) moieties act as an electron donor and acceptor, resp. The emission maxima of dyads 1 and 3 red-shifted with the increase in polarity, which could be attributed to the ICT process. The fluorescence lifetimes of dyads 1 and 3 were 2.64 and 4.29 ns in CH2Cl2, resp. In contrast, dyad 2 showed dual emission at 350 and 470 nm in CH2Cl2. The emission of dyad 2 at 380 nm corresponded to the monomer fluorescence in the locally excited state. Moreover, the emission at 470 nm increased simultaneously with the diminishing of the fluorescence at 380 nm. This emission band can be assigned as the intramol. exciplex emission, and showed a strong solvatochromic shift. The low emission quantum yield (<3%) of dyad 2 is due to the PET process. In dyad 2, the cationic and anionic radical species generated by the PET process were confirmed by femtosecond transient absorption (fs-TA) spectroscopy. Upon photoexcitation at 290 or 340 nm, the A or D moieties can be selectively excited. Upon excitation at 290 nm, the acceptor moiety can be excited to the 1A* state, thus the photoinduced hole transfer (PHT) takes place from 1A* to D through the HOMO levels within a few picoseconds. On the other hand, when the donor moiety is excited at 340 nm, the PET process occurs from 1D* to A. Based on the fs-TA studies, it was found that the dynamics and mechanisms for the electron (or charge) transfer were strongly affected by the variation of the π-conjugation of the linker. Herein, we can conclude that the PET and ICT processes are strongly influenced by the π-conjugation properties and their mechanisms are also affected by whether selective excitation of the donor or acceptor moiety occurs. Moreover, unit electron transfers (PET or PHT) were obsd. dominantly in the dyads having severed/twisted linkers in π-conjugation. However, dyad 1 possessing a well-conjugated linker showed a partial charge transfer character.
- 8Wex, B.; Kaafarani, B. R. Perspective on Carbazole-Based Organic Compounds as Emitters and Hosts in TADF Applications. J. Mater. Chem. C 2017, 5, 8622– 8653, DOI: 10.1039/C7TC02156AGoogle Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtFGhs7rK&md5=0085dec79f565d58e7ea9d58df313b00Perspective on carbazole-based organic compounds as emitters and hosts in TADF applicationsWex, Brigitte; Kaafarani, Bilal R.Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2017), 5 (34), 8622-8653CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)A review. The field of org. light-emitting devices (OLEDs) has undergone a remarkable journey since its discovery by Tang and Van Slyke with an alternation of using fluorescence and phosphorescence as the emitting vehicle. The latest generation of thermally activated delayed fluorescence (TADF) materials harvest triplet excited states back into the singlet manifold. This booming field has yielded a large array of new compds. as both emitters and hosts. This review is limited to TADF emitters using ≥1 carbazole unit as a donor and organized according to the various acceptor building blocks such as cyanophenyl, pyridine, biphenyls, anthraquinone, phenyl(pyridine-2-yl)methanone, benzophenone, xanthon, sulfones, triazines, benzils, dicyanopyrazines, diazatriphenylene, and others. A survey of carbazole-contg. host materials follows. D. functional theory (DFT) has carved out a significant role in allowing the theor. prediction of ground state properties for materials applied in OLED technol. Time-dependent DFT extends the reach to model excited state properties important to rationalize the light-output in OLED technol. For TADF, 2 fundamental factors are of interest: significant sepn. of frontier MOs and min. singlet-triplet energy gap (ΔEST). In this review, the use of DFT calcns. to optimize geometries for the visualization of frontier MO sepn. was surveyed to find that the B3LYP/6-31G(d) level of theory is the overwhelmingly used approach. The authors review the more in-depth approaches to using DFT and time-dependent DFT (TD-DFT) with optimized percentage Hartree-Fock (OHF) and long-range cor. hybrid functionals, tuning procedures and others in an attempt to best quantify the size of ΔEST as well as the nature of the triplet state as locally excited state (LE) and charge-transfer state (CT).
- 9Saigo, M.; Miyata, K.; Tanaka, S.; Nakanotani, H.; Adachi, C.; Onda, K. Suppression of Structural Change Upon S1–T1 Conversion Assists the Thermally Activated Delayed Fluorescence Process in Carbazole-Benzonitrile Derivatives. J. Phys. Chem. Lett. 2019, 10, 2475– 2480, DOI: 10.1021/acs.jpclett.9b00810Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXntFarurg%253D&md5=7e9323775e0a0c53ec73e07867eb791cSuppression of Structural Change upon S1-T1 Conversion Assists the Thermally Activated Delayed Fluorescence Process in Carbazole-Benzonitrile DerivativesSaigo, Masaki; Miyata, Kiyoshi; Tanaka, Sei'ichi; Nakanotani, Hajime; Adachi, Chihaya; Onda, KenJournal of Physical Chemistry Letters (2019), 10 (10), 2475-2480CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)Thermally activated delayed fluorescence (TADF) mols. are gathering attention for their potential to boost the efficiency of org. light-emitting diodes without precious metals. Minimizing the energy difference between the S1 and T1 states (ΔEST) is a fundamental strategy to accelerate reverse intersystem crossing (RISC). However, the lack of microscopic understanding of the process prevents adequate design strategies for efficient TADF materials. Here, the authors focused on four carbazole-benzonitrile (Cz-BN) derivs. that possess identical ΔEST but distinct TADF activities. The authors systematically compared their geometrical dynamics upon photoexcitation using time-resolved IR (TR-IR) vibrational spectroscopy in conjunction with quantum chem. calcns. The most TADF-active mol., 4CzBN, shows little structural change after photoexcitation, while the TADF-inactive mols. show relatively large deformation upon S1-T1 conversion. This implies that the suppression of structural deformation is crit. for minimizing the activation energy barrier for RISC in cases of the Cz-BN derivs.
- 10Bhattacharjee, I.; Acharya, N.; Bhatia, H.; Ray, D. Dual Emission through Thermally Activated Delayed Fluorescence and Room-Temperature Phosphorescence, and Their Thermal Enhancement via Solid-State Structural Change in a Carbazole-Quinoline Conjugate. J. Phys. Chem. Lett. 2018, 9, 2733– 2738, DOI: 10.1021/acs.jpclett.8b00937Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXptVCiurw%253D&md5=ee6b47ac9d44de49dade55ac7e588224Dual Emission through Thermally Activated Delayed Fluorescence and Room-Temperature Phosphorescence, and Their Thermal Enhancement via Solid-State Structural Change in a Carbazole-Quinoline ConjugateBhattacharjee, Indranil; Acharya, Nirmalya; Bhatia, Harsh; Ray, DebdasJournal of Physical Chemistry Letters (2018), 9 (11), 2733-2738CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)The emergence of single-component org. dual light emitters holds great promise for white light-emitting diodes (WLEDs) and biol. detection due to the involvement of broad emission covering visible spectrum. Here the authors show exptl. studies on dual emission of carbazole-quinoline conjugate (CQ) that exhibits both thermally activated delayed fluorescence (TADF) via reverse intersystem crossing (rISC) from the higher-lying triplet state (T2) to the singlet state (S1) and room-temp. phosphorescence (RTP) from the lowest triplet state (T1) due to low energy gap between T2 and S1, and energetic proximity of T1 with T2. The authors found in thermal effect that the intensity of the dual features is enhanced with increasing temps. up to 100°, which can be explained by a thermal-induced structural change (TISC) mechanism that compensates the emission losses due to nonradiative transitions at elevated temps. This property, in addn. to its enhanced TADF and phosphorescence decay rates (∼107 s-1and 101 s-1) at 100°, would have great promise for high-efficiency LEDs.
- 11Pashazadeh, R.; Pander, P.; Lazauskas, A.; Dias, F. B.; Grazulevicius, J. V. Multicolor Luminescence Switching and Controllable Thermally Activated Delayed Fluorescence Turn on/Turn Off in Carbazole–Quinoxaline–Carbazole Triads. J. Phys. Chem. Lett. 2018, 9, 1172– 1177, DOI: 10.1021/acs.jpclett.8b00136Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXjtVWitL0%253D&md5=03c7d29f39bc25982bcfc65d8abb9f9dMulticolor Luminescence Switching and Controllable Thermally Activated Delayed Fluorescence Turn on/Turn off in Carbazole-Quinoxaline-Carbazole TriadsPashazadeh, Ramin; Pander, Piotr; Lazauskas, Algirdas; Dias, Fernando B.; Grazulevicius, Juozas V.Journal of Physical Chemistry Letters (2018), 9 (5), 1172-1177CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)Thermally-activated delayed fluorescence (TADF) mols. with mechanochromic luminescence properties and reversible TADF turn on/off properties in solid state that are induced by the transition between amorphous and cryst. states are reported. Multicolor altering through external stimulus is demonstrated. All of the studied compds. exhibited recovery of the initial states assocd. with narrower emission spectra. TADF org. light-emitting diodes fabricated by soln. processing rendered high external quantum efficiency ≤10.9% and luminance of 16,760 cd m-2.
- 12Jung, S.-H.; Kim, H. K. Novel Silicon-Based Copolymer for Tunable Light-Emitting Diodes: Synthesis and Characterization. J. Lumin. 2000, 87-89, 51– 55, DOI: 10.1016/S0022-2313(99)00222-7Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXislWgtbs%253D&md5=a4086d3d36dc9125156d6699ad7be387Novel silicon-based copolymers for tunable light-emitting diodes: synthesis and characterizationJung, S.-H.; Kim, H. K.Journal of Luminescence (2000), 87-89 (), 51-55CODEN: JLUMA8; ISSN:0022-2313. (Elsevier Science B.V.)Si-based alternating copolymers sol. in org. solvents were synthesized by Heck reaction to use as electroluminescent materials. They could spin cast onto various substrates to give highly transparent homogeneous thin films. The present polymers exhibit UV-visible strong absorption bands around 325-380 nm, which corresponds to the π-π* transition of the π-conjugated segment, since the π-conjugated system is interrupted by organosilicon units. Their photoluminescence spectra appeared around 440-476 nm in the blue emission region. The multi-layered light-emitting diodes of a Al/LiAl/SiPhPVK(poly(3,6-diformyl-N-(2-ethylhexyl)-carbazolyl)tetraphenylsilane)/PANI(polyaniline) /ITO glass and a Al/LiAl/SiPhFPV(poly(9,9-dihexyl-fluorenyl)tetraphenylsilane)/ITO glass are fabricated. The threshold voltage is at 6-12 V from the I-V curve. The electroluminescence spectra of the SiPhFPV give the highest peak in the blue EL emissive band at 486 nm, when the operating voltage of 6 V is applied. For the SiPhPVK contg. a carbazole unit, the EL spectrum of the polymer shows the highest peak in the blue EL emissive band at 467 nm as well as an addnl. strong emissive band in the yellow region, when the operating voltage of 11 V is applied.
- 13Jung, S.-H.; Kim, H. K.; Kim, S.-H.; Kim, Y. H.; Jeoung, S. C.; Kim, D. Palladium-Catalyzed Direct Synthesis, Photophysical Properties, and Tunable Electroluminescence of Novel Silicon-Based Alternating Copolymers. Macromolecules 2000, 33, 9277– 9288, DOI: 10.1021/ma0003248Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXotVyht7w%253D&md5=8dd50b00ba9f17e9f2ca34684156018aPalladium-Catalyzed Direct Synthesis, Photophysical Properties, and Tunable Electroluminescence of Novel Silicon-Based Alternating CopolymersJung, Sung-Hyun; Kim, Hwan Kyu; Kim, Sung-Hyun; Kim, Yong Hee; Jeoung, Sae Chae; Kim, DonghoMacromolecules (2000), 33 (25), 9277-9288CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)A new class of silicon-based alternating copolymers with a uniform π-conjugated segment regulated by organosilicon units was synthesized using the Heck reaction between distyrylsilane monomers and appropriate arylene dibromides. The incorporation of organosilicon units with the arom. or aliph. groups on the silicon atoms into π-conjugated systems improved their processability and interrupted the π-conjugation length. They could be spin-cast onto various substrates to give highly transparent homogeneous thin films. Their glass transition temps. were in the range 94-127 °C. They show strong absorption bands around 356-416 nm, which corresponds to the π-π* transition of the conjugated segments. The max. photoluminescence appeared around 440-526 nm in the blue or green emission region. Their optical properties depend on the arylene dibromides in the Heck reaction. The single-layered light-emitting diode of an Al/SiPhPPV or SiHMPPV/ITO glass exhibits a threshold voltage of 10-12 V from the I-V curve. The electroluminescence (EL) of the SiPhPPV or SiHMPPV gives an emissive peak at 450 nm. Furthermore, the multilayered light-emitting diodes of an Al/LiAl/SiPhPVK/PANI/ITO glass and an Al/LiAl/SiPhFPV or SiHMFPV/ITO glass shows a threshold voltage of 6-12 V. The EL device based on SiPhPVK exhibits the blue emissive color at 467 nm, when an operating voltage of 7 V was applied. When an operating voltage of 11 V was applied, however, the EL device emits a white color. The EL spectra of the SiPhFPV and SiHMFPV polymers, obtained at an applied voltage of 12 V, show two strong peaks in the blue emissive region as well as in the green region.
- 14Akcelrud, L. Electroluminescent Polymers. Prog. Polym. Sci. 2003, 28, 875– 962, DOI: 10.1016/S0079-6700(02)00140-5Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjsVWisr8%253D&md5=cfbc028044e9135fdd3ba9d5e84b2837Electroluminescent polymersAkcelrud, LeniProgress in Polymer Science (2003), 28 (6), 875-962CODEN: PRPSB8; ISSN:0079-6700. (Elsevier Science Ltd.)A review. Electroluminescent polymers are reviewed in terms of synthesis and relationships between structure and light emission properties in electroluminescent devices. The main concepts, problems, and ideas related to the subject as a whole and to each class of electroluminescent polymer have been systematically addressed.
- 15Maeda, H.; Suzuki, T.; Segi, M. Effects of Substituents in Silyl Groups on the Absorption, Fluorescence and Structural Properties of 1,3,6,8-Tetrasilylpyrenes. Photochem. Photobiol. Sci. 2018, 17, 781– 792, DOI: 10.1039/C8PP00135AGoogle Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXosl2muro%253D&md5=9d840dc6acdc23a97ff50580e7d0188eEffects of substituents in silyl groups on the absorption, fluorescence and structural properties of 1,3,6,8-tetrasilylpyrenesMaeda, Hajime; Suzuki, Tsubasa; Segi, MasahitoPhotochemical & Photobiological Sciences (2018), 17 (6), 781-792CODEN: PPSHCB; ISSN:1474-905X. (Royal Society of Chemistry)1,3,6,8-Tetrasilylpyrenes and related germyl and stannyl derivs. were synthesized, and their absorption and fluorescence spectroscopic and structural properties were elucidated. The results show that the UV-vis absorption maxima of these substances in CH2Cl2 solns. shift to longer wavelengths as the size of the alkyl groups and nos. of Ph groups on silicon increase. Fluorescence quantum yields of tetrasilylpyrenes in cyclohexane are larger than that of pyrene, and a pentamethyldisilyl deriv. has an emission efficiency of 0.79. Except in the case of the SiMe2H deriv., excimer emission was not obsd. in concd. solns. of these substances. The SiMe2H and SiMe3 derivs. were shown to form CT complexes with tetracyanoethylene in CH2Cl2 solns. The calcd. energy barriers for rotation of the silyl groups about the Si-C bond increase as the steric bulk of the silyl group increases. 29Si NMR chem. shifts were found to depend on the sizes of the alkyl groups and nos. of Ph groups. Data arising from theor. calcns. suggest that the silyl groups act as electron-donating groups, and the donating ability of the groups decreases in the order SiR3 > GeR3 > SnR3.
- 16Maeda, H.; Ueno, R.; Furuyama, T.; Segi, M. Effects of Substituents on Absorption and Fluorescence Properties of Trimethylsilylethynyl- and Tert-Butylethynyl-Pyrenes. J. Photochem. Photobiol. A 2020, 392, 112428 DOI: 10.1016/j.jphotochem.2020.112428Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXisFSjs78%253D&md5=01cd555466efc12a0b4983ae69db9573Effects of substituents on absorption and fluorescence properties of trimethylsilylethynyl- and tert-butylethynyl-pyrenesMaeda, Hajime; Ueno, Ryota; Furuyama, Taniyuki; Segi, MasahitoJournal of Photochemistry and Photobiology, A: Chemistry (2020), 392 (), 112428CODEN: JPPCEJ; ISSN:1010-6030. (Elsevier B.V.)Effects of substituents introduced at 1-position of trimethylsilylethynyl- and tert-butylethynyl-pyrenes on absorption and fluorescence properties were investigated. Fluorescence intensities of 1.0 × 10-5 M CH2Cl2 solns. of these pyrene derivs. were significantly larger than that of pyrene. Absorption of a silyl deriv. having a formyl group shifted to longer wavelengths as the solvent polarity increased, whereas that of the carbon analog shifted to shorter wavelengths. On the other hand, in the solvent dependence of fluorescence, both fluorescence of them shifted to longer wavelengths as the polarity of the solvent increased. Fluorescence spectra of pyrene derivs. synthesized in this study at satd. concns. in CH2Cl2 exhibited excimer emissions in the longer wavelength regions compared to that of unsubstituted pyrene. Fluorescence quantum yields of silicon analogs were higher than that of the corresponding carbon analogs in both soln. and solid states. From the results of MO calcns., it was clarified that the effects of the substituents at the 1-position on the pyrene ring on the absorption and fluorescence properties can be explained by the properties of the MOs corresponding to the resp. electron transitions.
- 17Shimizu, M.; Tatsumi, H.; Mochida, K.; Hiyama, T. Solid State Structures and Photophysical Properties of (Trimethylsilyl)Methyl-Substituted Anthracenes and Pyrenes. Chem. Commun. 2008, 2134– 2136, DOI: 10.1039/b716770aGoogle Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXltFynsLk%253D&md5=a5b4bd9dc9d74487c2d07fedb204b412Solid state structures and photophysical properties of (trimethylsilyl)methyl-substituted anthracenes and pyrenesShimizu, Masaki; Tatsumi, Hironori; Mochida, Kenji; Hiyama, TamejiroChemical Communications (Cambridge, United Kingdom) (2008), (18), 2134-2136CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)(Trimethylsilyl)methyl groups incorporated at 9- and 9,10-positions of anthracenes and at 1,3,6,8-positions of pyrenes were found to orient perpendicular to the arom. frameworks in their crystals and induce red-shift of UV absorption and fluorescence spectra and enhancement of fluorescence quantum yields as compared with the parent hydrocarbons.
- 18Li, J.-J.; Zhang, H.-Y.; Liu, G.; Dai, X.; Chen, L.; Liu, Y. Photocontrolled Light-Harvesting Supramolecular Assembly Based on Aggregation-Induced Excimer Emission. Adv. Optical Mater. 2021, 9, 2001702– 2001708, DOI: 10.1002/adom.202001702Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXisVert7fO&md5=2ef75625a7e8842752ca5190bcb2490dPhotocontrolled Light-Harvesting Supramolecular Assembly Based on Aggregation-Induced Excimer EmissionLi, Jing-Jing; Zhang, Heng-Yi; Liu, Guoxing; Dai, Xianyin; Chen, Lei; Liu, YuAdvanced Optical Materials (2021), 9 (2), 2001702CODEN: AOMDAX; ISSN:2195-1071. (Wiley-VCH Verlag GmbH & Co. KGaA)Photocontrolled light-harvesting supramol. assembly with aggregation-induced excimer emission is fabricated by polyanionic γ-cyclodextrin (COONa-γ-CD), pyrene deriv. (PYC12), Nile red (NiR), and diarylethene deriv. (DAE) in aq. soln. Benefiting from the COONa-γ-CD-induced aggregation of PYC12, the fluorescence can be modulated from monomeric state to assembled state with a large red-shift around 100 nm, which exhibits aggregation-induced excimer emission enhancement and makes PYC12 a remarkable energy donor. Subsequently, NiR can function as energy acceptor loaded into PYC12/COONa-γ-CD supramol. assembly, and highly efficient energy transfer process occurs from PYC12/COONa-γ-CD to NiR, with energy transfer efficiency up to 83% at donor/acceptor ratio of 160:1. Moreover, multicolor tunable emission can be achieved simply by tuning the molar ratios of donor and acceptor, notably including white-light emission. Interestingly, loading photoresponsive energy acceptor DAE into PYC12/COONa-γ-CD/NiR assembly endows the light-harvesting system with excellent photocontrolled energy transfer, and this process can be efficiently regulated upon distinct light irradn.
- 19Liu, Y.; Liu, H.; Bai, Q.; Du, C.; Shang, A.; Jiang, D.; Tang, X.; Lu, P. Pyrene[4,5-D]Imidazole-Based Derivatives with Hybridized Local and Charge-Transfer State for Highly Efficient Blue and White Organic Light-Emitting Diodes with Low Efficiency Roll-Off. ACS Appl. Mater. Interfaces 2020, 12, 16715– 16725, DOI: 10.1021/acsami.0c01846Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXkvFyis7w%253D&md5=1b94bf36f72ff52efa10ac9122b96088Pyrene[4,5-d]imidazole-Based Derivatives with Hybridized Local and Charge-Transfer State for Highly Efficient Blue and White Organic Light-Emitting Diodes with Low Efficiency Roll-OffLiu, Yulong; Liu, Hui; Bai, Qing; Du, Chunya; Shang, Anqi; Jiang, Dongyan; Tang, Xiangyang; Lu, PingACS Applied Materials & Interfaces (2020), 12 (14), 16715-16725CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)A family of pyrene[4,5-d]imidazole derivs., PyPA, PyPPA, PyPPAC, and PyPAC, with different excited states are successfully developed. Among them, PyPPA and PyPPAC possess hybridized local and charge-transfer (HLCT) state, endowing them with pure blue fluorescence as well as high quantum yields. The nondoped org. light-emitting diode (OLED) based on PyPPA displays Commission Internationale de L'Eclairage coordinates of (0.14, 0.13) and achieves a max. external quantum efficiency (EQE) of 8.47%, which are among the highest value reported to date for nondoped blue HLCT OLEDs. The nondoped OLED based on PyPPAC exhibits a max. luminance of 50,046 cd m-2 located in the blue region with CIE coordinates of (0.15, 0.21) and an EQE of 6.74% even when the luminance reached over 10,000 cd m-2. In addn., they both reveal ultimate exciton utilizing efficiencies of nearly 100%. The potential of a blue emitter of PyPPA with an HLCT character for application in white OLED (WOLED) is further tested. The efficient two-color hybrid warm WOLED is successfully achieved, which provides the total EQE, power efficiency, and current efficiency of up to 21.19%, 61.46 lm W-1, and 62.13 cd A-1, resp. The nondoped blue OLEDs and hybrid WOLEDs present good color stabilities with low efficiency roll-offs. Our results prove that taking advantage of the HLCT state, nondoped blue OLEDs as well as hybrid WOLEDs with high performance could be realized, which have a promising prospect for the displays and lightings in the future.
- 20Wu, Y.; Li, X.; Zhao, H.; Li, J.; Miao, Y.; Wang, H.; Zhu, F.; Xu, B. Pyrene-Based Hyperbranched Porous Polymers with Doped Ir(Piq)2(acac) Red Emitter for Highly Efficient White Polymer Light-Emitting Diodes. Org. Electron. 2020, 76, 105487– 105495, DOI: 10.1016/j.orgel.2019.105487Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhvFGms73K&md5=caabf78a73904e6d45133a0e8bb39695Pyrene-based hyperbranched porous polymers with doped Ir(piq)2(acac) red emitter for highly efficient white polymer light-emitting diodesWu, Yuling; Li, Xuefeng; Zhao, Haocheng; Li, Jie; Miao, Yanqin; Wang, Hua; Zhu, Furong; Xu, BingsheOrganic Electronics (2020), 76 (), 105487CODEN: OERLAU; ISSN:1566-1199. (Elsevier B.V.)Here, we designed and prepd. a series of hyperbranched porous polymers constructed using fluorene branches and pyrene core, and all hyperbranched porous polymers exhibit intense blue fluorescence, good morphol. stability, and high thermal stability. Further, it is found that the aperture sizes for hyperbranched porous polymers can be adjusted by simply changing the content of pyrene and fluorene in the synthesis process. When the feed ratios of pyrene in the total polymers is 15 mol%, the optimized aperture size was obtained, which is slightly larger than the maxlength of complementary red emitter Bis(1-phenylisoquinoline)(acetylacetonate)iridium (III) (Ir(piq)2acac), indicating the Ir(piq)2acac can well distributed in the apertures of hyperbranched porous polymers in co-doped film of Ir(piq)2acac and hyperbranched porous polymers. The fabricated polymer-light-emitting diode (PLED) with such co-doped film as light-emitting layer realizes good white emission with almost equal blue and red emission intensity from hyperbranched porous polymers and Ir(piq)2acac. The balanced electroluminescent (EL) spectra contribute to ideal Commission Internationale de l'Eclairage (CIE) coordinate of (0.326, 0.374) located at white light zone. In addn., the device also achieves high device performance with max. luminance and current efficiency reaching 5369 cd/m2 and 8.35 cd/A, resp. We believe that such porous-structure polymers have huge potential applications in the development of highly efficient white PLEDs with reducing prodn. cost.
- 21Kumar, V.; Sk, B.; Kundu, S.; Patra, A. Dynamic and Static Excimer: A Versatile Platform for Single Component White-Light Emission and Chelation-Enhanced Fluorescence. J. Mater. Chem. C 2018, 6, 12086– 12094, DOI: 10.1039/C8TC03035AGoogle Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvVOjt7fF&md5=5d2de664f5c65e86468758281aaaae28Dynamic and static excimer: a versatile platform for single component white-light emission and chelation-enhanced fluorescenceKumar, Virendra; Sk, Bahadur; Kundu, Subhankar; Patra, AbhijitJournal of Materials Chemistry C: Materials for Optical and Electronic Devices (2018), 6 (44), 12086-12094CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)The present study demonstrates the tuning of iconic optical features of pyrene through its judicious assembly with a C3-sym. triaminoguanidinium ion, leading to the development of a unique multifunctional luminescent material PYTG. By fine tuning the concn. and the external stimuli, such as temp., the addn. of analytes led to a dramatic change in the fluorescence of PYTG, providing an excellent platform for the exploration of the dynamic and static excimer formation. Recently, white-light-emitting mol. probes have received considerable attention from the scientific community due to their great potentials in display devices. Tripodal PYTG was employed as a pure white-light emitter consisting of blue emission from monomers and orange emission from excimers both in soln. and thin film with Commission Internationale de l'Eclairage (CIE) coordinates of (0.33, 0.34) and (0.33, 0.38), resp. The formation of a dynamic excimer along with monomer fluorescence at higher concns. of PYTG led to tunable emission. Addnl., the rich electronic properties of PYTG allowed efficient detection of trivalent metal ions by turn-on fluorescence and colorimetric sensing of fluoride ions. PYTG selectively detected Fe3+ and Al3+ with nanomolar sensitivity in a semi-aq. soln. via a chelation-enhanced fluorescence response in the orange-red region (λem = 588 nm) by static excimer formation. The 'on-off' fluorescence switching by the consecutive addn. of trivalent cations and a chelating ligand EDTA makes PYTG a promising fluorescent mol. switch. A simple and cost-effective strategy, leading to the development of a versatile fluorescent probe and an in-depth exploration of the structure-property relationship as delineated in the present manuscript, will pave the way for the emergence of novel task-specific mol. optical materials.
- 22Feng, X.; Qi, C.; Feng, H.-T.; Zhao, Z.; Sung, H. H. Y.; Williams, I. D.; Kwok, R. T. K.; Lam, J. W. Y.; Qin, A.; Tang, B. Z. Dual Fluorescence of Tetraphenylethylene-substituted Pyrenes with Aggregation-Induced Emission Characteristics for White-Light Emission. Chem. Sci. 2018, 9, 5679– 5687, DOI: 10.1039/C8SC01709CGoogle Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtVGisL7O&md5=1a55a288ea8b7e8b83af7b68dd13b2d8Dual fluorescence of tetraphenylethylene-substituted pyrenes with aggregation-induced emission characteristics for white-light emissionFeng, Xing; Qi, Chunxuan; Feng, Hai-Tao; Zhao, Zheng; Sung, Herman H. Y.; Williams, Ian D.; Kwok, Ryan T. K.; Lam, Jacky W. Y.; Qin, Anjun; Tang, Ben ZhongChemical Science (2018), 9 (25), 5679-5687CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)This article presents a new strategy to achieve white-light emission from single tetraphenylethylene-substituted pyrenes (TPE-Pys) with aggregation-induced emission (AIE) characteristics. TPE-Pys were synthesized by a Pd-catalyzed coupling reaction of a boronic acid or pinacol ester of pyrene and tetraphenylethylene (TPE) derivs. and showed multicolor emission by introducing different substituents on the Ph rings of TPE. TPE-Pys with a TPE unit at the 1-position and asym. TPE units at 2,7-positions show dual fluorescence in THF/water mixts. to realize white-light emission with CIE coordinates of (x = 0.30 and y = 0.41) and (x = 0.21 and y = 0.16), resp. The structure-property relationship of TPE-Pys were investigated to elucidate the origin of the white emission. The results showed that due to the weak electronic interaction of pyrene and its chromophoric units at the 2,7-positions and the constraint of the rotation of the TPE unit at the 1-position of pyrene, each component can exhibit its own emission color. The combination of appropriate colors gives rise to white-light emission. Such a principle of mol. design may open a new avenue for prepg. advanced multicolor and multifunctional optical materials for org. electronics.
- 23You, J.; Li, G.; Wang, R.; Nie, Q.; Wang, Z.; Li, J. Pyrene-Cored Dendrimer with Carbazole Derivatives as Dendrons: Synthesis, Properties and Application in White Light-Emitting Diode. Phys. Chem. Chem. Phys. 2011, 13, 17825– 17830, DOI: 10.1039/c1cp21848dGoogle Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXht1eqtb7M&md5=22d5065583a812a27a0dda34cb7c3f7cPyrene-cored dendrimer with carbazole derivatives as dendrons: synthesis, properties and application in white light-emitting diodeYou, Jia; Li, Guiyang; Wang, Renjie; Nie, Qiuping; Wang, Zhonggang; Li, JiuyanPhysical Chemistry Chemical Physics (2011), 13 (39), 17825-17830CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)A new dendrimer using pyrene as core and carbazole deriv. as dendron was successfully prepd. via Suzuki coupling reaction. Its chem. structure was confirmed through 1H NMR, elemental anal. and MALDI-TOF MS methods. The dendrimer synthesized possessed excellent thermal stability with initial decompn. temp. over 470° and high fluorescence quantum yield of 86%. The luminescence spectra showed that, relative to the soln. sample, the emission peaks of the solid dendrimer film were apparently broadened and red-shifted, indicating the strong π-π stacking effect between the pyrene moieties. By doping 1.5% of the dendrimer in 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), a light-emitting diode device was fabricated in the ITO/NPB/NPB : dendrimer (1.5%)/TPBI/Mg : Ag configuration, which emitted a white color with Commission Internationale de L'Eclairage (CIEx,y) coordinates of (0.29, 0.34) and a max. brightness of 1300 cd m-2, exhibiting promising potential in white light-emitting diode application.
- 24Unny, D.; Kandregula, G. R.; Sivanadanam, J.; Ramanujam, K. Molecular Engineering of Pyrene Carbazole Dyes with a Single Bond and Double Bond as the Mode of Linkage. New J. Chem. 2020, 44, 16511– 16525, DOI: 10.1039/D0NJ03228JGoogle Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhs1ehurzM&md5=a412c98bffc73b3f154e4fa6d20d8f25Molecular engineering of pyrene carbazole dyes with a single bond and double bond as the mode of linkageUnny, Divya; Kandregula, Ganapathi Rao; Sivanadanam, Jagadeeswari; Ramanujam, KothandaramanNew Journal of Chemistry (2020), 44 (38), 16511-16525CODEN: NJCHE5; ISSN:1144-0546. (Royal Society of Chemistry)Both carbazole and pyrene are electron-rich arom. systems and are expected to be potential donors when used in a push-pull dye architecture in the field of DSSC technol. Herein, two novel pyrene-carbazole dyes bearing single bond (PC1) and double bond (PC2) linkers and cyano-acrylic acid as an acceptor were synthesized. The dye with a double bond spacer (PC2) in the presence of CDCA achieved an improved power conversion efficiency of 6.30% with a short circuit current of 11.59 mA cm-2, open circuit potential (VOC) of 0.80 V, and a fill factor of 0.68 under std. global AM 1.5G solar conditions. Cyclic voltammetry and d. functional theory studies indicate that the incorporation of two donors improved the ease of oxidn. of the dyes, which resulted in a high VOC. Despite having a rigid single bond, the charge transfer of the PC1 dye is found to be poor, which affected the photovoltaic performance. The dihedral angle measured at each joint of the optimized dye indicated that PC2 exhibits excellent intramol. charge transfer due to the near planarity in the structure. Besides, the high electron lifetime in the excited state of PC2 makes it the best performer among the three dyes studied.
- 25Zhao, Z.; Xu, X.; Wang, H.; Lu, P.; Yu, G.; Liu, Y. Zigzag Molecules from Pyrene-Modified Carbazole Oligomers: Synthesis, Characterization, and Application in OLEDs. J. Org. Chem. 2008, 73, 594– 602, DOI: 10.1021/jo702075rGoogle Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhsVCrsLvK&md5=5003eede45905eb95877639fc9bb2751Zigzag Molecules from Pyrene-Modified Carbazole Oligomers: Synthesis, Characterization, and Application in OLEDsZhao, Zujin; Xu, Xinjun; Wang, Hongbo; Lu, Ping; Yu, Gui; Liu, YunqiJournal of Organic Chemistry (2008), 73 (2), 594-602CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)A series of monodisperse, pyrene-modified oligocarbazoles was synthesized and fully characterized. Carbazoles were linked by ethynylene through the 3- and 6-positions, forming a zigzag mol. backbone and stable, size-independent absorption, and emission were obsd. from these oligomers in solns. because their conjugation length was confined. Oligomers with pyrene exhibited much higher fluorescence quantum yields than those of oligomers without it. Different positions of pyrene in the oligocarbazole main chain resulted in a remarkable change in absorption and emission spectra. Moreover, devices with four different architectures based on these oligomers were fabricated and investigated. Pyrene-modified carbazole oligomers exhibited bifunctional properties (light-emitting and hole-transport). Moreover, these devices showed moderate performances; for example,the device based on Cz3PyCz3 (I) presented an external quantum efficiency of 0.69% and a max. brightness of 1782 cd/m2 at 13.5 V, which indicated these oligomers were promising optoelec. materials.
- 26Valsange, N. G. A New Pyrene Cored Small Organic Molecule with a Flexible Alkyl Spacer: A Potential Solution Processable Blue Emitter with Bright Photoluminescence. New J. Chem. 2017, 41, 11383– 11390, DOI: 10.1039/C7NJ01921AGoogle Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsVejurvM&md5=102a6c8df2cd41facf459d2d8c347c20A new pyrene cored small organic molecule with a flexible alkyl spacer: a potential solution processable blue emitter with bright photoluminescenceValsange, Nitin G.; Wong, F. L.; Shinde, Durgaprasad; Lee, C. S.; Roy, V. A. L.; Manzhos, Sergei; Feron, K.; Chang, Samuel; Katoh, Ryuzi; Sonar, Prashant; Wadgaonkar, Prakash P.New Journal of Chemistry (2017), 41 (19), 11383-11390CODEN: NJCHE5; ISSN:1144-0546. (Royal Society of Chemistry)A new pyrene cored small org. mol. viz. 1,3,6,8-tetrakis(4-((5-(9H-carbazol-9-yl)pentyl)oxy)phenyl)pyrene (PY-II) was designed and synthesized. The carbazole moiety with an alkyl spacer was introduced at 1, 3, 6 and 8 positions of the pyrene core to improve the charge transport properties and soln. processability. PY-II exhibited excellent soly. in common org. solvents and high thermal stability up to 345°. The photoluminescence quantum yield (PLQY) of PY-II in soln. is 0.9 with bright blue emission near 450 nm which is just appropriate for the human eye. The soln. processed non-doped OLED device fabricated using PY-II as an emissive layer afforded a pure blue emission with CIE coordinates of 0.16 and 0.16, a power efficiency of 0.17 lm W-1, a max. current efficiency of 0.41 cd A-1 and a max. brightness of 202 cd m-2.
- 27Kotchapradist, P.; Prachumrak, N.; Tarsang, R.; Jungsuttiwong, S.; Keawin, T.; Sudyoadsuk, T.; Promarak, V. Pyrene-Functionalized Carbazole Derivatives as Non-Doped Blue Emitters for Highly Efficient Blue Organic Light-Emitting Diodes. J. Mater. Chem. C 2013, 1, 4916– 4924, DOI: 10.1039/c3tc30719kGoogle Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFKns77F&md5=aab2ba25107f379cec983accbb0be414Pyrene-functionalized carbazole derivatives as non-doped blue emitters for highly efficient blue organic light-emitting diodesKotchapradist, Palita; Prachumrak, Narid; Tarsang, Ruangchai; Jungsuttiwong, Siriporn; Keawin, Tinnagon; Sudyoadsuk, Taweesak; Promarak, VinichJournal of Materials Chemistry C: Materials for Optical and Electronic Devices (2013), 1 (32), 4916-4924CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)Pyrene-functionalized carbazole derivs., N-dodecyl-3,6-di(pyren-1-yl)carbazole (CP2), N-dodecyl-1,3,6-tri(pyren-1-yl)carbazole (CP3) and N-dodecyl-1,3,6,8-tetra(pyren-1-yl)carbazole (CP4), are synthesized and characterized as simple nondoped soln. processed blue emitters for OLEDs. By multiple substitution of pyrene on the carbazole ring, the authors are able to retain the high blue emissive ability of pyrene in the solid as well as improve the amorphous stability and soly. of the material. These materials show high soln. fluorescence quantum efficiencies (up to 94%) and can form morphol. stable amorphous thin films with Tg ≤ 170°. Soln. processed double-layer OLEDs using these materials as nondoped blue emitters exhibit good device performance with luminance efficiencies up to 2.53 cd A-1. Their multi-layer devices exhibit outstanding performances. The CP2-based device shows a low turn-on voltage (down to 2.6 V) with an excellent blue emission color (λem = 436 nm) and CIE coordinates of (0.16, 0.14), while the CP3 and CP4-based blue devices also display low turn-on voltages (down to 2.7 V) with high luminance (up to 24479 cd m-2) and luminance efficiencies (up to 6.92 cd A-1).
- 28Kaafarani, B. R. Bis(Tercarbazole) Pyrene and Tetrahydropyrene Derivatives: Photophysical and Electrochemical Properties, Theoretical Modeling, and OLEDs. J. Mater. Chem. C 2019, 7, 5009– 5018, DOI: 10.1039/C8TC06266HGoogle Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXlsFeqtr0%253D&md5=201753419955731a6b96bb9b2069dce9Bis(tercarbazole) pyrene and tetrahydropyrene derivatives: photophysical and electrochemical properties, theoretical modeling, and OLEDsKaafarani, Bilal R.; El-Assaad, Tarek H.; Smith, William A.; Ryno, Sean M.; Hermerschmidt, Felix; Lyons, Jeffrey; Patra, Digambara; Wex, Brigitte; List-Kratochvil, Emil J. W.; Risko, Chad; Barlow, Stephen; Marder, Seth R.Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2019), 7 (17), 5009-5018CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)2,7-Bis(3,3'',6,6''-tetra(tert-butyl)-9'H-9,3':6',9''-tercarbazol-9-yl)-4,5,9,10-tetrahydropyrene I and 2,7-bis(3,3'',6,6''-tetra(tert-butyl)-9'H-9,3':6',9''-tercarbazol-9-yl)pyrene II, along with a model compd., 3,3'',6,6''-tetra(tert-butyl)-9'-(4-(tert-butyl)phenyl)-9'H-9,3':6',9''-tercarbazole III, were synthesized using microwave-assisted palladium-catalyzed coupling and compared to analogous 3,6-di(tert-butyl)carbazol-9-yl species. Time-dependent d. functional theory (TDDFT) calcns. revealed absorption with quadrupolar (ter)carbazole-to-bridge CT character. Compd. II was unusual in showing dual fluorescence in a no. of solvents; the longer wavelength feature of which was markedly more solvatochromic than the bands of other compds. Following the obsd. three oxidns. on TCz model compd. III, compds. I and II could be electrochem. reversibly oxidized to hexacations with four oxidn. and three oxidn. steps in a 2 : 2 : 1 : 1 and a 2 : 2 : 2 current ratio, resp. Tercarbazole derivs. I and II had been used as the emissive layers of simple soln.-processed few-layer org. light-emitting diodes.
- 29Joseph, V.; Thomas, K. R. J.; Sahoo, S.; Singh, M.; Jou, J.-H. Cyano-Functionalized Carbazole Substituted Pyrene Derivatives for Promising Organic Light-Emitting Diodes. Dyes Pigm. 2018, 158, 295– 305, DOI: 10.1016/j.dyepig.2018.05.038Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtVKrsbjJ&md5=abfe27712d29ce2ebee7b709a1516db9Cyano-functionalized carbazole substituted pyrene derivatives for promising organic light-emitting diodesJoseph, Vellaichamy; Thomas, K. R. Justin; Sahoo, Snehasis; Singh, Meenu; Jou, Jwo-HueiDyes and Pigments (2018), 158 (), 295-305CODEN: DYPIDX; ISSN:0143-7208. (Elsevier Ltd.)Balanced charge transport is crucial to realize efficient org. light-emitting diodes. In this work, pyrene derivs. featuring variable no. of cyano-functionalized carbazoles are synthesized and characterized by photophys., electrochem., thermal and electroluminescence studies. The compds. displayed progressive variation in absorption and emission wavelength reflecting the effect of chromophore loading. The electroluminescence color change from deep blue to green on varying the no./position of cyanocarbazole units on pyrene. 1,6-Disubstituted deriv. exhibited blue shift in absorption and emission when compared to the 1,8-analog. The current efficiency and power efficiency of the devices progressively increase on increasing the cyanocarbazole load on pyrene. It is probably originating from the balanced charge transport due to the increase in the no. of cyanocarbazole units on pyrene and effective harvest of excitons in emissive layer. The best electroluminescence performance of the doped device fabricated from tetra-substituted deriv. (1 wt%) displayed relatively high power efficiency (5.8 lm/W) and current efficiency (9.2 cd/A).
- 30Zhang, T.; Ye, J.; Luo, A.; Liu, D. Efficient Deep Blue Emitter Based on Carbazole-Pyrene Hybrid for Non-Doped Electroluminescent Device. Opt. Mater. 2020, 100, 109632– 109637, DOI: 10.1016/j.optmat.2019.109632Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlWjtw%253D%253D&md5=ee659aadc3a499b771c87745e189caa4Efficient deep blue emitter based on carbazole-pyrene hybrid for non-doped electroluminescent deviceZhang, Ting; Ye, Jieyang; Luo, Ansheng; Liu, DiOptical Materials (Amsterdam, Netherlands) (2020), 100 (), 109632CODEN: OMATET; ISSN:0925-3467. (Elsevier B.V.)A new deep blue fluorescent material based on carbazole-pyrene hybrid, namely PyEtCz, was synthesized by palladium catalyzed C-C Suzuki coupling reaction, and structurally characterized by NMR, mass spectra and elemental anal. The thermal stability, photophys. and optoelectronic properties were fully investigated. The material shows good thermal stability and can form an amorphous glass state. Its CH2Cl2 soln. exhibits strong deep-blue emission with high fluorescent quantum yield of 75%. PyEtCz also possesses high HOMO level of -5.48 eV that would facilitate efficient hole injection into the emitting layer. The non-doped OLED using PyEtCz as emitter through vacuum evapn. was fabricated for purpose of investigating its electroluminescence properties. The device exhibited stable blue electroluminescence with CIE coordinate of (0.15, 0.10), a good performance with max. luminance of 6573 cd m-2 and max. luminance efficiency of 3.24 cd A-1 (3.35%) was achieved.
- 31Rachuta, K.; Bayda, M.; Majchrzak, M.; Koput, J.; Marciniak, B. Unusual Emission Properties of the Selected Organosilicon Compounds Containing a Styryl-Carbazole Chromophore: Inversion of the Singlet Excited States. Phys. Chem. Chem. Phys. 2017, 19, 11698– 11705, DOI: 10.1039/C7CP01292FGoogle Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXlslCrt70%253D&md5=0971f6a4aaf51a54f20b1b7e09a5cfd7Unusual emission properties of the selected organosilicon compounds containing a styryl-carbazole chromophore: inversion of the singlet excited statesRachuta, K.; Bayda, M.; Majchrzak, M.; Koput, J.; Marciniak, B.Physical Chemistry Chemical Physics (2017), 19 (18), 11698-11705CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)The spectroscopic and photophys. properties of silicon-contg. styryl-carbazole were investigated in various solvents, and the results were analyzed with ref. to its carbon derivs. In n-hexane, both the silicon- and the carbon-contg. compds. had very similar emission properties. In acetonitrile, the emission properties remained the same for the C-compd. but changed significantly for the Si-compds. In particular, the fluorescence spectra of the latter were red-shifted, and their radiative rate consts. were even 7 times larger than in n-hexane, which suggested that the emissive states of the silicon-contg. compds. were different in these two solvents. DFT calcns. using the CAM-B3LYP functional showed that the emissive state of the C-compd. involves the LUMO+1 orbital regardless of the medium. In contrast, for the Si-compd., changing the medium from n-hexane to acetonitrile resulted in the inversion of the emissive states from an excited state involving the LUMO+1 orbital (the dipole moment μ = 4.2 D) to an excited state involving the LUMO orbital (μ = 8.9 D).
- 32Eaton, D. F. Reference Materials for Fluorescence Measurement. Pure Appl. Chem. 1988, 60, 1107– 1114, DOI: 10.1351/pac198860071107Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1cXlsFyrtL0%253D&md5=51ba5738e8da49584e6393251022a47fReference materials for fluorescence measurementEaton, David F.Pure and Applied Chemistry (1988), 60 (7), 1107-14CODEN: PACHAS; ISSN:0033-4545.A review with 19 refs. is given on std. practices and materials for fluorescence measurements and the avoidance of exptl. inadequacies attendant on their application in practical use. Appropriate methods are discussed which strike a balance between ease of application, generality of use, and reliability.
- 33Rachuta, K.; Bayda-Smykaj, M.; Majchrzak, M.; Koput, J.; Marciniak, B. Emission Properties of Si-Based Styryl-Carbazole Derivatives: Role of Meta- and Para-Vinyl Substituents and Silicon Atom. J. Lumin. 2018, 196, 57– 63, DOI: 10.1016/j.jlumin.2017.12.007Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvF2ntr3P&md5=2fb4e18a07b8e68a40385c11831294fdEmission properties of Si-based styryl-carbazole derivatives: Role of meta- and para-vinyl substituents and silicon atomRachuta, K.; Bayda-Smykaj, M.; Majchrzak, M.; Koput, J.; Marciniak, B.Journal of Luminescence (2018), 196 (), 57-63CODEN: JLUMA8; ISSN:0022-2313. (Elsevier B.V.)A series of styryl-carbazole derivs. (with and without a silicon atom) were investigated in n-hexane and in acetonitrile in terms of their spectroscopic and photophys. properties. The major question addressed in this work is how the presence of a trimethylsilyl group modifies the absorption and emission properties of styryl-carbazoles depending whether vinyl groups are in a meta- or para- position. It was obsd. that only para-styryl-carbazole contg. silicon undergoes a solvent-induced inversion of its lowest singlet excited states whereas meta-styryl-carbazole contg. silicon retains the properties of the meta-styryl-carbazole itself. The different character of the emissive state was deduced from its 7-fold larger radiative rate const. in acetonitrile compared to results in n-hexane. DFT calcns. revealed on the mol. level why inversion of the excited states occurs only for this silicon-based styryl-carbazole whose vinyl group is in the para- and not in the meta- position.
- 34Berlman, I. B., Handbook of Florescence Spectra of Aromatic Molecules; Academic Press: New York and London, 1971.Google ScholarThere is no corresponding record for this reference.
- 35Parker, C. A.; Hatchard, C. G. Delayed Fluorescence of Pyrene in Ethanol. Trans. Faraday Soc. 1963, 59, 284– 295, DOI: 10.1039/tf9635900284Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF3sXktVKls7Y%253D&md5=c3177bd5359a90bcd16337cd7bbda394Delayed fluorescence of pyrene in ethanolParker, C. A.; Hatchard, C. G.Transactions of the Faraday Society (1963), 59 (), 284-95CODEN: TFSOA4; ISSN:0014-7672.cf. CA 55, 19879f. Normal and delayed fluorescence at room temp. showed bands due to singlet excited monomer and excited dimer. At low pyrene concn. the relative intensity of the normal fluorescence of the dimer tends to zero, but the relative intensity of the delayed fluorescence of the dimer was almost const. The intensity of delayed fluorescence of both monomer and dimer was proportional to the sq. of the rate of absorption of exciting light. The delayed fluorescence was due to triplet-triplet quenching which resulted in the formation of excited dimer mols., some of which fluoresce and some of which dissoc. into excited and ground-state singlet mols. The delayed fluorescence of anthracene and phenanthrene solns. has the same mechanism.
- 36Sun, Y.-P.; Sears, J.; D. F; Saltiel, J. Three-Component Self-Modeling Technique Applied to Luminescence Spectra. Anal. Chem. 1987, 59, 2515– 2519, DOI: 10.1021/ac00147a015Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2sXlsVCju7w%253D&md5=81269f70235a229572134af4d7dd7be0Three-component self-modeling technique applied to luminescence spectraSun, Ya Ping; Sears, Donald F., Jr.; Saltiel, JackAnalytical Chemistry (1987), 59 (20), 2515-19CODEN: ANCHAM; ISSN:0003-2700.The selection of pure component spectral coeffs. was improved when addnl. applicable constraints were imposed. The method was demonstrated for a 2-component system (the phosphorescence and delayed fluorescence of benzophenone) and extended to 3 components. It succeeded in reproducing theor. curves used to construct an artificial 3-component input matrix, and it was applied to resolve exptl. spectra composed of the fluorescence of 2 conformers of trans-1,2-di-2-naphthylethene and a background spectrum dominated by Raman emission at the excitation wavelength region.
- 37Catalán, J.; Zimányi, L.; Saltiel, J. Medium Controlled Aggregation of Trans Stilbene. J. Am. Chem. Soc. 2000, 122, 2377– 2378, DOI: 10.1021/ja991834oGoogle Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXhtlKjsLc%253D&md5=dc78333d6c6f832079c61c90d018981bMedium-Controlled Aggregation of trans-StilbeneCatalan, Javier; Zimanyi, Laszlo; Saltiel, JackJournal of the American Chemical Society (2000), 122 (10), 2377-2378CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)UV and fluorescence spectra of trans-stilbene solns. in isopentane at low temps. (98-110 K) undergo changes indicative of face to edge monomer assocn. A model based on rate detg. photodimerization and dimer monomer assocn. to trimer is discussed.
- 38Zimányi, L.; Kulcsár, Á.; Lanyi, J. K.; Sears, J.; D. F; Saltiel, J. Singular Value Decomposition with Self-Modeling Applied to Determine Bacteriorhodopsin Intermediate Spectra. Analysis of Simulated Data. Proc. Natl. Acad. Sci. U. S. A. 1999, 96, 4408– 4413, DOI: 10.1073/pnas.96.8.4408Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXjs1ylsrg%253D&md5=3d547b26bf19c0ea26f0d676c7f78426Singular value decomposition with self-modeling applied to determine bacteriorhodopsin intermediate spectra: analysis of simulated dataZimanyi, Laszlo; Kulcsar, Agnes; Lanyi, Janos K.; Sears, Donald F., Jr.; Saltiel, JackProceedings of the National Academy of Sciences of the United States of America (1999), 96 (8), 4408-4413CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)An a priori model-independent method for the detn. of accurate spectra of photocycle intermediates is developed. The method, singular value decompn. with self-modeling (SVD-SM), is tested on simulated difference spectra designed to mimic the photocycle of the Asp-96 → Asn mutant of bacteriorhodopsin. Stoichiometric constraints, valid until the onset of the recovery of bleached bacteriorhodopsin at the end of the photocycle, guide the self-modeling procedure. The difference spectra of the intermediates are detd. in eigenvector space by confining the search for their coordinates to a stoichiometric plane. In the absence of random noise, SVD-SM recovers the intermediate spectra and their time evolution nearly exactly. The recovery of input spectra and kinetics is excellent although somewhat less exact when realistic random noise is included in the input spectra. The difference between recovered and input kinetics is now visually discernible, but the same reaction scheme with nearly identical rate consts. to those assumed in the simulation fits the output kinetics well. SVD-SM relegates the selection of a photocycle model to the late stage of the anal. In thus avoids derivation of erroneous model-specific spectra that result from global model-fitting approaches that assume a model at the outset.
- 39Liu, K.-L.; Lee, S.-J.; Chen, I.-C.; Hsu, C.-P.; Yeh, M.-Y.; Luh, T.-Y. Ultrafast Energy Transfer in a Regioregular Silylene-Spaced Copolymer. J. Phys. Chem. C 2010, 114, 13909– 13916, DOI: 10.1021/jp102376xGoogle Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXpsVKksL0%253D&md5=a4db845332d50fb4900afb2eec52fd47Ultrafast Energy Transfer in a Regioregular Silylene-Spaced CopolymerLiu, Kuan-Lin; Lee, Sheng-Jui; Chen, I.-Chia; Hsu, Chao-Ping; Yeh, Mei-Yu; Luh, Tien-YauJournal of Physical Chemistry C (2010), 114 (32), 13909-13916CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)The energy-transfer properties of a regioregular silylene-spaced alternating donor-acceptor copolymer (donor-SiMe2-acceptor-SiMe2)m are detd. with time-resolved spectroscopy; 4,4'-divinylbiphenyl serves as donor and 4,4'-divinylstilbene as acceptor. Steady-state fluorescence spectra show that the energy transfer is efficient. With excitation at 266 nm, fluorescence up-conversion curves at various detection wavelengths are measured to explore the detailed dynamics of the energy transfer. A rate ∼(0.3 ps)-1 for energy transfer between the S1 states of the donor and acceptor moieties is obsd. Theor. calcns. based on fragment excitation difference provide a rate of energy transfer near the exptl. value with detailed insight into the mechanism of energy transfer. The results of theor. calcns. indicate that the Coulomb interaction is dominant and the Dexter process is weak. The high-multipole interactions are important for energy transfer.
- 40Lakowicz, J. R., Principles of Fluorescence Spectroscopy; Kluwer Academik/Plenum Publisher: New York, 1999.Google ScholarThere is no corresponding record for this reference.
- 41Yoshihara, T.; Druzhinin, S. I.; Demeter, A.; Kocher, N.; Stalke, D.; Zachariasse, K. A. Kinetics of Intramolecular Charge Transfer with N-Phenylpyrrole in Alkyl Cyanides. J. Phys. Chem. A 2005, 109, 1497– 1509, DOI: 10.1021/jp046586jGoogle Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXhtVKlt7k%253D&md5=39507e9af3bc82d5e10ef0908e62088dKinetics of Intramolecular Charge Transfer with N-Phenylpyrrole in Alkyl CyanidesYoshihara, Toshitada; Druzhinin, Sergey I.; Demeter, Attila; Kocher, Nikolaus; Stalke, Dietmar; Zachariasse, Klaas A.Journal of Physical Chemistry A (2005), 109 (8), 1497-1509CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)For the electron acceptor/donor mol. N-phenylpyrrole (PP), the fast intramol. charge transfer (ICT) reaction accompanied by dual fluorescence from a locally excited (LE) and an ICT state is investigated in alkyl cyanide solvents as a function of temp. After a comparison of the x-ray crystal structure of PP with calcns. from the literature, absorption and fluorescence spectra of PP in a series of solvents over a wide polarity range are discussed. ICT with PP strongly depends on solvent polarity and starts to appear in solvents more polar than di-Et ether. From an anal. of the ICT/LE fluorescence quantum yield ratio Φ'(ICT)/Φ(LE), approx. data for the change in enthalpy -ΔH of the ICT reaction of PP are obtained, ranging from 9 kJ/mol in acetonitrile to 4 kJ/mol in Bu cyanide. From ICT and LE fluorescence decays of PP measured as a function of temp., the forward (Ea = 9 kJ/mol in Et cyanide (EtCN) and 6 kJ/mol in MeCN) and backward (Ed = 16 kJ/mol in EtCN and MeCN) ICT reaction barriers are detd. From these data, -ΔH (7 kJ/mol (EtCN); 10 kJ/mol (MeCN)) is calcd., in good agreement with the results coming from Φ'(ICT)/Φ(LE). The data for Ea show that the forward ICT barrier becomes smaller with increasing solvent polarity, whereas the absence of change for Ed comes from the compensating increase of -ΔH. Both observations are indicative of a late transition state for the LE → ICT reaction. For PP in EtCN and MeCN, the ICT radiative rate const. k'f(ICT) increases with temp. This is caused by the ICT low transition dipole moment and hence does not contain information on the mol. structure (twisted or planar) of the ICT state. The fast ICT obsd. with PP supports our previous conclusion, based on a comparison of PP with its planarized deriv. fluorazene, that the pyrrole and Ph moieties in the ICT state of PP are coplanar and possess substantial electronic coupling.
- 42Bayda, M.; Angulo, G.; Hug, G. L.; Ludwiczak, M.; Karolczak, J.; Koput, J.; Dobkowski, J.; Marciniak, B. Electron Transfer in Silicon-Bridged Adjacent Chromophores: The Source for Blue-Green Emission. Phys. Chem. Chem. Phys. 2017, 19, 11404– 11415, DOI: 10.1039/C7CP00590CGoogle Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXlsVars74%253D&md5=3b1710da709ca08e1f61d0c41265f5f0Electron transfer in silicon-bridged adjacent chromophores: the source for blue-green emissionBayda, Malgorzata; Angulo, Gonzalo; Hug, Gordon L.; Ludwiczak, Monika; Karolczak, Jerzy; Koput, Jacek; Dobkowski, Jacek; Marciniak, BronislawPhysical Chemistry Chemical Physics (2017), 19 (18), 11404-11415CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Si-Bridged chromophores were proposed as sources for blue-green emission in several technol. applications. The origin of this dual emission is to be found in an internal charge transfer reaction. The current work is an attempt to describe the details of these processes in these kinds of substances, and to design a mol. architecture to improve their performance. Nuclear motions essential for intramol. charge transfer (ICT) can involve processes from twisted internal moieties to dielec. relaxation of the solvent. To address these issues, the authors studied ICT between adjacent chromophores in a mol. compd. contg. N-isopropylcarbazole (CBL) and 1,4-divinylbenzene (DVB) linked by a dimethylsilylene bridge. In nonpolar solvents emission arises from the local excited state (LE) of carbazole whereas in solvents of higher polarity dual emission was detected (LE + ICT). The CT character of the addnl. emission band was concluded from the linear dependence of the fluorescence maxima on solvent polarity. Electron transfer from CBL to DVB resulted in a large excited-state dipole moment (37.3 D) as detd. from a solvatochromic plot and DFT calcns. Steady-state and picosecond time-resolved fluorescence expts. in butyronitrile (293-173 K) showed that the ICT excited state arises from the LE state of carbazole. These results were analyzed and are in accordance with an adiabatic version of Marcus theory including solvent relaxation.
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Abstract
Figure 1
Figure 1. White-light emission of compound 1 in ACN.
Chart 1
Chart 1. Structures of the Investigated Compound 1 and Its Reference Compounds 1a and 1bFigure 2
Figure 2. Absorption spectra of compounds 1, 1a, and 1b in ACN.
Figure 3
Figure 3. Normalized fluorescence spectra (top panel) and energy diagrams (bottom panel) of compounds 1 (red line), 1a (light gray line), and 1b (dark gray line) in hexane (a,a1), DCM (b,b1), and ACN (c,c1). The colors of the energy diagrams correspond to colors of the spectral contours presented in the top panel.
Figure 4
Figure 4. Time-resolved fluorescence spectra of compound 1 in ACN (λexc = 330 nm).
Figure 5
Figure 5. Resolved fluorescence spectra of pure CT1 and CT2 states obtained from SVD-SM and experimental calculations and steady-state fluorescence spectrum of 1b (a); combination coefficients (α, β, γ) of the normalized emission spectra presented as points in a 3D vector space spanned by the three most significant eigenvectors of the covariance matrix (b). The colors of the three spheres in (b) correspond to colors of the spectral contours in (a). The corners of the triangle correspond to the spectra of the pure components.
Figure 6
Figure 6. Fluorescence decays of compound 1 in ACN, λem = 420 and 560 nm and λexc = 330 nm.
Scheme 1
Scheme 1. Mechanism of the Photoinduced Processes of Compound 1 in ACN (λexc = 330 nm)aa(LE = emission from the local excited state; ET = energy transfer; HT = hole transfer; e̅= electron transfer; and CT1, CT2 = charge-transfer excited states).
References
This article references 42 other publications.
- 1Bayda-Smykaj, M.; Burdzinski, G.; Ludwiczak, M.; Hug, G. L.; Marciniak, B. Early Events in the Photoinduced Electron Transfer between Carbazole and Divinylbenzene in a Silylene-Bridged Donor-Acceptor Compound. J. Phys. Chem. C 2020, 124, 19522– 19529, DOI: 10.1021/acs.jpcc.0c075311https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhs1aqsL%252FI&md5=d48bfaf37b44f80b1f12cb39e5c0cb7fEarly Events in the Photoinduced Electron Transfer between Carbazole and Divinylbenzene in a Silylene-Bridged Donor-Acceptor CompoundBayda-Smykaj, Malgorzata; Burdzinski, Gotard; Ludwiczak, Monika; Hug, Gordon L.; Marciniak, BronislawJournal of Physical Chemistry C (2020), 124 (36), 19522-19529CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Meeting the challenge of designing new light-emitting materials, we synthesized the compd. N-isopropylcarbazole (CBL)-SiMe2-divinylbenzene (DVB), which represents the general idea of building attractive emitters by stitching together simple, well-known block elements. Following this strategy, an extraordinary emission emerges from photoinduced intramol. processes between silylene-bridged adjacent chromophores, e.g., intramol. energy and/or electron transfer (PET). The reported compd. displays an attractive blue emission that occurs no matter which of the linked chromophores is excited (i.e., regardless of the excitation wavelength in the range 240-360 nm). Excitation of CBL leads directly to intramol. charge transfer (ICT) state formation within 35 ps, whereas excitation of DVB results in "pumping" the CBL excited state via 300 fs energy transfer. In the latter case, DVB acts as an intramol. photosensitizer of the ICT precursor. Both mechanisms, proceeding via ultrafast processes, are confirmed by femtosecond transient absorption expts. performed on the investigated bichromophoric compd. and its individual Si-contg. chromophores in acetonitrile soln. Anal. of the transient absorption bands allowed us to characterize the ICT excited state as a radical ion pair of carbazole radical cation and divinylbenzene radical anion linked by a silylene bridge.
- 2Fakis, M.; Beckwith, J. S.; Seintis, K.; Martinou, E.; Nançoz, C.; Karakostas, N.; Petsalakis, I.; Pistolis, G.; Vauthey, E. Energy Transfer and Charge Separation Dynamics in Photoexcited Pyrene-Bodipy Molecular Dyads. Phys. Chem. Chem. Phys. 2018, 20, 837– 849, DOI: 10.1039/C7CP06914F2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFWgtbnF&md5=be06938f856ead74b5620e365a346ef5Energy transfer and charge separation dynamics in photoexcited pyrene-bodipy molecular dyadsFakis, M.; Beckwith, J. S.; Seintis, K.; Martinou, E.; Nancoz, C.; Karakostas, N.; Petsalakis, I.; Pistolis, G.; Vauthey, E.Physical Chemistry Chemical Physics (2018), 20 (2), 837-849CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)The photophys. properties of two pyrene-bodipy mol. dyads, composed of a phenyl-pyrene (Py-Ph) linked to the meso position of a bodipy (BD) mol. with either H-atoms (BD1) or Et groups (BD2) at the 2,6 positions, are investigated by stationary, nanosecond and femtosecond spectroscopy. The properties of these dyads (Py-Ph-BD1 and Py-Ph-BD2) are compared to those of their constituent chromophores in two solvents namely 1,2-dichloroethane (DCE) and acetonitrile (ACN). Stationary spectroscopy reveals a weak coupling among the subunits in both dyads. Excitation of the pyrene (Py) subunit leads to emission that is totally governed by the BD subunits in both dyads pointing to excitation energy transfer (EET) from the Py to BD chromophore. Femtosecond fluorescence and transient absorption spectroscopy reveal that EET takes place within 0.3-0.5 ps and is mostly independent of the solvent and the type of the BD subunit. The EET lifetime is in reasonable agreement with that predicted by Forster theory. After EET has taken place, Py-Ph-BD1 in DCE and Py-Ph-BD2 in both solvents decay mainly radiatively to the ground state with 3.5-5.0 ns lifetimes which are similar to those of the individual BD chromophores. However, the excited state of Py-Ph-BD1 in ACN is quenched having a lifetime of 1 ns. This points to the opening of an addnl. non-radiative channel of the excited state of Py-Ph-BD1 in this solvent, most probably charge sepn. (CS). Target anal. of the TA spectra has shown that the CS follows inverted kinetics and is substantially slower than the recombination of the charge-sepd. state. Occurrence of CS with Py-Ph-BD1 in ACN is also supported by energetic considerations. The above results indicate that only a small change in the structure of the BD units incorporated in the dyads significantly affects the excited state dynamics leading either to a dyad with long lifetime and high fluorescence quantum yield or to a dyad with ability to undergo CS.
- 3Cho, J.; Park, J. H.; Kim, J. K.; Schubert, E. F. White Light-Emitting Diodes: History, Progress, and Future. Laser Photonics Rev. 2017, 11, 1600147 DOI: 10.1002/lpor.201600147There is no corresponding record for this reference.
- 4Paik, K. L.; Baek, N. S.; Kim, H. K.; Lee, J.-H.; Lee, Y. White Light-Emitting Diodes from Novel Silicon-Based Copolymers Containing Both Electron-Transport Oxadiazole and Hole-Transport Carbazole Moieties in the Main Chain. Macromolecules 2002, 35, 6782– 6791, DOI: 10.1021/ma020406r4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XlslKisrw%253D&md5=11db643629fe5603cb24ec935a2ba403White Light-Emitting Diodes from Novel Silicon-Based Copolymers Containing Both Electron-Transport Oxadiazole and Hole-Transport Carbazole Moieties in the Main ChainPaik, Kyung Lim; Baek, Nam Seob; Kim, Hwan Kyu; Lee, Ji-Hoon; Lee, YoungilMacromolecules (2002), 35 (18), 6782-6791CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)Si-based alternating copolymers contg. both electron-transport oxadiazole and hole-transport carbazole moieties in the main chain (SiHMOXD/Cz 10-01) were synthesized by the Heck coupling reaction. The resulting polymers exhibit a strong UV-visible absorption band at 345-356 nm in CHCl3 soln. and in film state. Their PL spectra show a max. band around 435-485 nm in the blue region. The light-emitting diodes of Al (200 nm)/Ca (50 nm)/EL polymer (80 nm)/PEDOT (50 nm)/ITO were successfully fabricated. And, J-V curves show a turn-on voltage of 6-7 V. Their EL properties depend strongly on both the applied voltage and the loading amt. of hole-transport carbazole moieties in the present copolymers. With the applied voltage, these emissive EL bands were red shifted from blue region to red region. Also, the intensity of a blue EL band at the relatively high operating voltages increases with the loading amt. of carbazole units. The LED device with the copolymer of SiHMOXD/Cz 19 exhibits the almost same intensity of two bands, like two crests, giving a strong white color. The blue EL color comes from the carbazole units in these Si-based copolymers. The latter red EL color comes from a specific charge complex with oxadiazole (and carbazole moieties). The new red band is exhibited only in EL but not in PL spectra. The EL device based on SiHMOXD/Cz 19 has a luminescence efficiency of 0.052 lm/W and a power efficiency of 0.13 cd/A at an applied voltage of 9 V And, the max. luminance of the white emissive color was 6.04 cd/m2 at an applied voltage of 17 V. From the photophys. studies, a specific intramol. charge complex is proposed.
- 5Chen, Z.-K.; Huang, W.; Wang, L.-H.; Kang, E.-T.; Chen, B. J.; Lee, C. S.; Lee, S. T. A Family of Electroluminescent Silyl-Substituted Poly(p-Phenylenevinylene)s; Synthesis, Characterization, and Structure-Property Relationships. Macromolecules 2000, 33, 9015– 9025, DOI: 10.1021/ma00056705https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXns1Ois7s%253D&md5=d28fdbbda94af133ed93be71eb733f69A Family of Electroluminescent Silyl-Substituted Poly(p-phenylenevinylene)s: Synthesis, Characterization, and Structure-Property RelationshipsChen, Z.-K.; Huang, W.; Wang, L.-H.; Kang, E.-T.; Chen, B. J.; Lee, C. S.; Lee, S. T.Macromolecules (2000), 33 (24), 9015-9025CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)A series of intense photoluminescent (PL) polymers contg. silyl groups with chain length from C1 to C18 was synthesized through polycondensation reaction. The silyl groups in the conjugated polymer provide for improved processability, amorphous morphol., good film-forming ability, and sharp emission. Increasing the side chain length resulted in a slight decrease of thermal stability while increasing the mol. wt. The UV-vis absorption and PL emission spectra of the polymers are quite similar. A cyclic voltammetry (CV) study of the polymers reveals that the side chain length plays an important role in the redox behavior of the polymers. The short side chain polymers possess better reproducibility of CV scans and higher peak currents, which implies that the chem./elec. stability and charge injection and/or transport are more efficient than those for long side chain polymers. Test devices were fabricated from poly[2,5-bis(decyldimethylsilyl)-1,4-phenylene vinylene] (DS-PPV) with the configuration of ITO/DS-PPV/Mg:Ag and ITO/PEDOT:PSS/DS-PPV/Mg:Ag. Measurements indicate that hole injection is the detg. factor in charge transport. Addn. of a hole injection layer can improve the current efficiency and power efficiency by about 7 times and lower the turn-on voltage from 7.5 to 4.0 V for the two types of devices.
- 6Cho, Y.-J.; Lee, A.-R.; Kim, S.-Y.; Cho, M.; Han, W.-S.; Son, H.-J.; Cho, D. W.; Kang, S. O. The Influence of π-Conjugation on Competitive Pathways: Charge Transfer or Electron Transfer in New D−π–A and D−π–Si−π–A Dyads. Phys. Chem. Chem. Phys. 2016, 18, 22921– 22928, DOI: 10.1039/C6CP03259A6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1egtrjK&md5=810bc1e2a03becc7e8162aa5124333c2The influence of π-conjugation on competitive pathways: charge transfer or electron transfer in new D-π-A and D-π-Si-π-A dyadsCho, Yang-Jin; Lee, Ah-Rang; Kim, So-Yoen; Cho, Minji; Han, Won-Sik; Son, Ho-Jin; Cho, Dae Won; Kang, Sang OokPhysical Chemistry Chemical Physics (2016), 18 (33), 22921-22928CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)In order to elucidate the influence of π-conjugation on photoinduced electron transfer (PET) and intramol. charge transfer processes, donor-π-acceptor dyads (D-π-A (1) and D-π-Si-π-A (2)) were newly synthesized. In these dyads, carbazole and triazine moieties acted as the electron donor and acceptor, resp. The fluorescence of dyad 1 red-shifted as the solvent polarity was increased. The electron charge distribution of the excited state of dyad 1 was delocalized in the acceptor moiety, forming the charge transfer Dδ+-π-Aδ- dyad in the excited state. In the excited state of dyad 1, the π-conjugation acted as the linker for charge transfer between the donor and acceptor moieties. A large dipole moment change (Δμ = 45.6 D) between the ground and excited states was detd. using the Lippert-Mataga plot. Furthermore, the fluorescence of dyad 1 was obsd. upon two-photon excitation. In contrast, dyad 2, in which the π-conjugation is disconnected by a Si-atom in the linker, displayed weak dual-emission: a short-wavelength emission at around 350 nm arising from the monomeric species and a long-wavelength one assigned to the emission from an intramol. exciplex between the donor and acceptor moieties. The weak emission of dyad 2 indicates that the D+̇ -π-Si-π-A-̇ species was generated through a PET process in the excited state. The cationic radical species of the carbazole and the anionic radical species of the triazine, which show transient absorption (TA) bands at around 780 and 530 nm, resp., were characterized using the femtosecond TA method.
- 7Kim, S.-Y.; Cho, Y.-J.; Lee, A.-R.; Son, H.-J.; Han, W.-S.; Cho, D. W.; Kang, S. O. Influence of π-Conjugation Structural Changes on Intramolecular Charge Transfer and Photoinduced Electron Transfer in Donor−π–Acceptor Dyads. Phys. Chem. Chem. Phys. 2017, 19, 426– 435, DOI: 10.1039/C6CP06566J7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvFCisrzE&md5=f30ef6d9ea5ff4b43ddd606c055d0c5cInfluence of π-conjugation structural changes on intramolecular charge transfer and photoinduced electron transfer in donor-π-acceptor dyadsKim, So-Yoen; Cho, Yang-Jin; Lee, Ah-Rang; Son, Ho-jin; Han, Won-Sik; Cho, Dae Won; Kang, Sang OokPhysical Chemistry Chemical Physics (2017), 19 (1), 426-435CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)The influence of π-conjugation structural changes on photoinduced electron transfer (PET) and intramol. charge transfer (ICT) processes in π-conjugated donor (D)-acceptor (A) dyads (D-π-A) was investigated. Three types of D-π-A dyads were prepd. through the modification of the structure of their π-conjugated linker, including D-π-A (1) and D-πtw-A (2) having a twisted π-conjugation, and D-π-Si-π-A (3) with a π-conjugation severed by a Si-atom. In these dyads, carbazole (Cz) and oxadiazole (Oz) moieties act as an electron donor and acceptor, resp. The emission maxima of dyads 1 and 3 red-shifted with the increase in polarity, which could be attributed to the ICT process. The fluorescence lifetimes of dyads 1 and 3 were 2.64 and 4.29 ns in CH2Cl2, resp. In contrast, dyad 2 showed dual emission at 350 and 470 nm in CH2Cl2. The emission of dyad 2 at 380 nm corresponded to the monomer fluorescence in the locally excited state. Moreover, the emission at 470 nm increased simultaneously with the diminishing of the fluorescence at 380 nm. This emission band can be assigned as the intramol. exciplex emission, and showed a strong solvatochromic shift. The low emission quantum yield (<3%) of dyad 2 is due to the PET process. In dyad 2, the cationic and anionic radical species generated by the PET process were confirmed by femtosecond transient absorption (fs-TA) spectroscopy. Upon photoexcitation at 290 or 340 nm, the A or D moieties can be selectively excited. Upon excitation at 290 nm, the acceptor moiety can be excited to the 1A* state, thus the photoinduced hole transfer (PHT) takes place from 1A* to D through the HOMO levels within a few picoseconds. On the other hand, when the donor moiety is excited at 340 nm, the PET process occurs from 1D* to A. Based on the fs-TA studies, it was found that the dynamics and mechanisms for the electron (or charge) transfer were strongly affected by the variation of the π-conjugation of the linker. Herein, we can conclude that the PET and ICT processes are strongly influenced by the π-conjugation properties and their mechanisms are also affected by whether selective excitation of the donor or acceptor moiety occurs. Moreover, unit electron transfers (PET or PHT) were obsd. dominantly in the dyads having severed/twisted linkers in π-conjugation. However, dyad 1 possessing a well-conjugated linker showed a partial charge transfer character.
- 8Wex, B.; Kaafarani, B. R. Perspective on Carbazole-Based Organic Compounds as Emitters and Hosts in TADF Applications. J. Mater. Chem. C 2017, 5, 8622– 8653, DOI: 10.1039/C7TC02156A8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtFGhs7rK&md5=0085dec79f565d58e7ea9d58df313b00Perspective on carbazole-based organic compounds as emitters and hosts in TADF applicationsWex, Brigitte; Kaafarani, Bilal R.Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2017), 5 (34), 8622-8653CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)A review. The field of org. light-emitting devices (OLEDs) has undergone a remarkable journey since its discovery by Tang and Van Slyke with an alternation of using fluorescence and phosphorescence as the emitting vehicle. The latest generation of thermally activated delayed fluorescence (TADF) materials harvest triplet excited states back into the singlet manifold. This booming field has yielded a large array of new compds. as both emitters and hosts. This review is limited to TADF emitters using ≥1 carbazole unit as a donor and organized according to the various acceptor building blocks such as cyanophenyl, pyridine, biphenyls, anthraquinone, phenyl(pyridine-2-yl)methanone, benzophenone, xanthon, sulfones, triazines, benzils, dicyanopyrazines, diazatriphenylene, and others. A survey of carbazole-contg. host materials follows. D. functional theory (DFT) has carved out a significant role in allowing the theor. prediction of ground state properties for materials applied in OLED technol. Time-dependent DFT extends the reach to model excited state properties important to rationalize the light-output in OLED technol. For TADF, 2 fundamental factors are of interest: significant sepn. of frontier MOs and min. singlet-triplet energy gap (ΔEST). In this review, the use of DFT calcns. to optimize geometries for the visualization of frontier MO sepn. was surveyed to find that the B3LYP/6-31G(d) level of theory is the overwhelmingly used approach. The authors review the more in-depth approaches to using DFT and time-dependent DFT (TD-DFT) with optimized percentage Hartree-Fock (OHF) and long-range cor. hybrid functionals, tuning procedures and others in an attempt to best quantify the size of ΔEST as well as the nature of the triplet state as locally excited state (LE) and charge-transfer state (CT).
- 9Saigo, M.; Miyata, K.; Tanaka, S.; Nakanotani, H.; Adachi, C.; Onda, K. Suppression of Structural Change Upon S1–T1 Conversion Assists the Thermally Activated Delayed Fluorescence Process in Carbazole-Benzonitrile Derivatives. J. Phys. Chem. Lett. 2019, 10, 2475– 2480, DOI: 10.1021/acs.jpclett.9b008109https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXntFarurg%253D&md5=7e9323775e0a0c53ec73e07867eb791cSuppression of Structural Change upon S1-T1 Conversion Assists the Thermally Activated Delayed Fluorescence Process in Carbazole-Benzonitrile DerivativesSaigo, Masaki; Miyata, Kiyoshi; Tanaka, Sei'ichi; Nakanotani, Hajime; Adachi, Chihaya; Onda, KenJournal of Physical Chemistry Letters (2019), 10 (10), 2475-2480CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)Thermally activated delayed fluorescence (TADF) mols. are gathering attention for their potential to boost the efficiency of org. light-emitting diodes without precious metals. Minimizing the energy difference between the S1 and T1 states (ΔEST) is a fundamental strategy to accelerate reverse intersystem crossing (RISC). However, the lack of microscopic understanding of the process prevents adequate design strategies for efficient TADF materials. Here, the authors focused on four carbazole-benzonitrile (Cz-BN) derivs. that possess identical ΔEST but distinct TADF activities. The authors systematically compared their geometrical dynamics upon photoexcitation using time-resolved IR (TR-IR) vibrational spectroscopy in conjunction with quantum chem. calcns. The most TADF-active mol., 4CzBN, shows little structural change after photoexcitation, while the TADF-inactive mols. show relatively large deformation upon S1-T1 conversion. This implies that the suppression of structural deformation is crit. for minimizing the activation energy barrier for RISC in cases of the Cz-BN derivs.
- 10Bhattacharjee, I.; Acharya, N.; Bhatia, H.; Ray, D. Dual Emission through Thermally Activated Delayed Fluorescence and Room-Temperature Phosphorescence, and Their Thermal Enhancement via Solid-State Structural Change in a Carbazole-Quinoline Conjugate. J. Phys. Chem. Lett. 2018, 9, 2733– 2738, DOI: 10.1021/acs.jpclett.8b0093710https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXptVCiurw%253D&md5=ee6b47ac9d44de49dade55ac7e588224Dual Emission through Thermally Activated Delayed Fluorescence and Room-Temperature Phosphorescence, and Their Thermal Enhancement via Solid-State Structural Change in a Carbazole-Quinoline ConjugateBhattacharjee, Indranil; Acharya, Nirmalya; Bhatia, Harsh; Ray, DebdasJournal of Physical Chemistry Letters (2018), 9 (11), 2733-2738CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)The emergence of single-component org. dual light emitters holds great promise for white light-emitting diodes (WLEDs) and biol. detection due to the involvement of broad emission covering visible spectrum. Here the authors show exptl. studies on dual emission of carbazole-quinoline conjugate (CQ) that exhibits both thermally activated delayed fluorescence (TADF) via reverse intersystem crossing (rISC) from the higher-lying triplet state (T2) to the singlet state (S1) and room-temp. phosphorescence (RTP) from the lowest triplet state (T1) due to low energy gap between T2 and S1, and energetic proximity of T1 with T2. The authors found in thermal effect that the intensity of the dual features is enhanced with increasing temps. up to 100°, which can be explained by a thermal-induced structural change (TISC) mechanism that compensates the emission losses due to nonradiative transitions at elevated temps. This property, in addn. to its enhanced TADF and phosphorescence decay rates (∼107 s-1and 101 s-1) at 100°, would have great promise for high-efficiency LEDs.
- 11Pashazadeh, R.; Pander, P.; Lazauskas, A.; Dias, F. B.; Grazulevicius, J. V. Multicolor Luminescence Switching and Controllable Thermally Activated Delayed Fluorescence Turn on/Turn Off in Carbazole–Quinoxaline–Carbazole Triads. J. Phys. Chem. Lett. 2018, 9, 1172– 1177, DOI: 10.1021/acs.jpclett.8b0013611https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXjtVWitL0%253D&md5=03c7d29f39bc25982bcfc65d8abb9f9dMulticolor Luminescence Switching and Controllable Thermally Activated Delayed Fluorescence Turn on/Turn off in Carbazole-Quinoxaline-Carbazole TriadsPashazadeh, Ramin; Pander, Piotr; Lazauskas, Algirdas; Dias, Fernando B.; Grazulevicius, Juozas V.Journal of Physical Chemistry Letters (2018), 9 (5), 1172-1177CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)Thermally-activated delayed fluorescence (TADF) mols. with mechanochromic luminescence properties and reversible TADF turn on/off properties in solid state that are induced by the transition between amorphous and cryst. states are reported. Multicolor altering through external stimulus is demonstrated. All of the studied compds. exhibited recovery of the initial states assocd. with narrower emission spectra. TADF org. light-emitting diodes fabricated by soln. processing rendered high external quantum efficiency ≤10.9% and luminance of 16,760 cd m-2.
- 12Jung, S.-H.; Kim, H. K. Novel Silicon-Based Copolymer for Tunable Light-Emitting Diodes: Synthesis and Characterization. J. Lumin. 2000, 87-89, 51– 55, DOI: 10.1016/S0022-2313(99)00222-712https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXislWgtbs%253D&md5=a4086d3d36dc9125156d6699ad7be387Novel silicon-based copolymers for tunable light-emitting diodes: synthesis and characterizationJung, S.-H.; Kim, H. K.Journal of Luminescence (2000), 87-89 (), 51-55CODEN: JLUMA8; ISSN:0022-2313. (Elsevier Science B.V.)Si-based alternating copolymers sol. in org. solvents were synthesized by Heck reaction to use as electroluminescent materials. They could spin cast onto various substrates to give highly transparent homogeneous thin films. The present polymers exhibit UV-visible strong absorption bands around 325-380 nm, which corresponds to the π-π* transition of the π-conjugated segment, since the π-conjugated system is interrupted by organosilicon units. Their photoluminescence spectra appeared around 440-476 nm in the blue emission region. The multi-layered light-emitting diodes of a Al/LiAl/SiPhPVK(poly(3,6-diformyl-N-(2-ethylhexyl)-carbazolyl)tetraphenylsilane)/PANI(polyaniline) /ITO glass and a Al/LiAl/SiPhFPV(poly(9,9-dihexyl-fluorenyl)tetraphenylsilane)/ITO glass are fabricated. The threshold voltage is at 6-12 V from the I-V curve. The electroluminescence spectra of the SiPhFPV give the highest peak in the blue EL emissive band at 486 nm, when the operating voltage of 6 V is applied. For the SiPhPVK contg. a carbazole unit, the EL spectrum of the polymer shows the highest peak in the blue EL emissive band at 467 nm as well as an addnl. strong emissive band in the yellow region, when the operating voltage of 11 V is applied.
- 13Jung, S.-H.; Kim, H. K.; Kim, S.-H.; Kim, Y. H.; Jeoung, S. C.; Kim, D. Palladium-Catalyzed Direct Synthesis, Photophysical Properties, and Tunable Electroluminescence of Novel Silicon-Based Alternating Copolymers. Macromolecules 2000, 33, 9277– 9288, DOI: 10.1021/ma000324813https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXotVyht7w%253D&md5=8dd50b00ba9f17e9f2ca34684156018aPalladium-Catalyzed Direct Synthesis, Photophysical Properties, and Tunable Electroluminescence of Novel Silicon-Based Alternating CopolymersJung, Sung-Hyun; Kim, Hwan Kyu; Kim, Sung-Hyun; Kim, Yong Hee; Jeoung, Sae Chae; Kim, DonghoMacromolecules (2000), 33 (25), 9277-9288CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)A new class of silicon-based alternating copolymers with a uniform π-conjugated segment regulated by organosilicon units was synthesized using the Heck reaction between distyrylsilane monomers and appropriate arylene dibromides. The incorporation of organosilicon units with the arom. or aliph. groups on the silicon atoms into π-conjugated systems improved their processability and interrupted the π-conjugation length. They could be spin-cast onto various substrates to give highly transparent homogeneous thin films. Their glass transition temps. were in the range 94-127 °C. They show strong absorption bands around 356-416 nm, which corresponds to the π-π* transition of the conjugated segments. The max. photoluminescence appeared around 440-526 nm in the blue or green emission region. Their optical properties depend on the arylene dibromides in the Heck reaction. The single-layered light-emitting diode of an Al/SiPhPPV or SiHMPPV/ITO glass exhibits a threshold voltage of 10-12 V from the I-V curve. The electroluminescence (EL) of the SiPhPPV or SiHMPPV gives an emissive peak at 450 nm. Furthermore, the multilayered light-emitting diodes of an Al/LiAl/SiPhPVK/PANI/ITO glass and an Al/LiAl/SiPhFPV or SiHMFPV/ITO glass shows a threshold voltage of 6-12 V. The EL device based on SiPhPVK exhibits the blue emissive color at 467 nm, when an operating voltage of 7 V was applied. When an operating voltage of 11 V was applied, however, the EL device emits a white color. The EL spectra of the SiPhFPV and SiHMFPV polymers, obtained at an applied voltage of 12 V, show two strong peaks in the blue emissive region as well as in the green region.
- 14Akcelrud, L. Electroluminescent Polymers. Prog. Polym. Sci. 2003, 28, 875– 962, DOI: 10.1016/S0079-6700(02)00140-514https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjsVWisr8%253D&md5=cfbc028044e9135fdd3ba9d5e84b2837Electroluminescent polymersAkcelrud, LeniProgress in Polymer Science (2003), 28 (6), 875-962CODEN: PRPSB8; ISSN:0079-6700. (Elsevier Science Ltd.)A review. Electroluminescent polymers are reviewed in terms of synthesis and relationships between structure and light emission properties in electroluminescent devices. The main concepts, problems, and ideas related to the subject as a whole and to each class of electroluminescent polymer have been systematically addressed.
- 15Maeda, H.; Suzuki, T.; Segi, M. Effects of Substituents in Silyl Groups on the Absorption, Fluorescence and Structural Properties of 1,3,6,8-Tetrasilylpyrenes. Photochem. Photobiol. Sci. 2018, 17, 781– 792, DOI: 10.1039/C8PP00135A15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXosl2muro%253D&md5=9d840dc6acdc23a97ff50580e7d0188eEffects of substituents in silyl groups on the absorption, fluorescence and structural properties of 1,3,6,8-tetrasilylpyrenesMaeda, Hajime; Suzuki, Tsubasa; Segi, MasahitoPhotochemical & Photobiological Sciences (2018), 17 (6), 781-792CODEN: PPSHCB; ISSN:1474-905X. (Royal Society of Chemistry)1,3,6,8-Tetrasilylpyrenes and related germyl and stannyl derivs. were synthesized, and their absorption and fluorescence spectroscopic and structural properties were elucidated. The results show that the UV-vis absorption maxima of these substances in CH2Cl2 solns. shift to longer wavelengths as the size of the alkyl groups and nos. of Ph groups on silicon increase. Fluorescence quantum yields of tetrasilylpyrenes in cyclohexane are larger than that of pyrene, and a pentamethyldisilyl deriv. has an emission efficiency of 0.79. Except in the case of the SiMe2H deriv., excimer emission was not obsd. in concd. solns. of these substances. The SiMe2H and SiMe3 derivs. were shown to form CT complexes with tetracyanoethylene in CH2Cl2 solns. The calcd. energy barriers for rotation of the silyl groups about the Si-C bond increase as the steric bulk of the silyl group increases. 29Si NMR chem. shifts were found to depend on the sizes of the alkyl groups and nos. of Ph groups. Data arising from theor. calcns. suggest that the silyl groups act as electron-donating groups, and the donating ability of the groups decreases in the order SiR3 > GeR3 > SnR3.
- 16Maeda, H.; Ueno, R.; Furuyama, T.; Segi, M. Effects of Substituents on Absorption and Fluorescence Properties of Trimethylsilylethynyl- and Tert-Butylethynyl-Pyrenes. J. Photochem. Photobiol. A 2020, 392, 112428 DOI: 10.1016/j.jphotochem.2020.11242816https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXisFSjs78%253D&md5=01cd555466efc12a0b4983ae69db9573Effects of substituents on absorption and fluorescence properties of trimethylsilylethynyl- and tert-butylethynyl-pyrenesMaeda, Hajime; Ueno, Ryota; Furuyama, Taniyuki; Segi, MasahitoJournal of Photochemistry and Photobiology, A: Chemistry (2020), 392 (), 112428CODEN: JPPCEJ; ISSN:1010-6030. (Elsevier B.V.)Effects of substituents introduced at 1-position of trimethylsilylethynyl- and tert-butylethynyl-pyrenes on absorption and fluorescence properties were investigated. Fluorescence intensities of 1.0 × 10-5 M CH2Cl2 solns. of these pyrene derivs. were significantly larger than that of pyrene. Absorption of a silyl deriv. having a formyl group shifted to longer wavelengths as the solvent polarity increased, whereas that of the carbon analog shifted to shorter wavelengths. On the other hand, in the solvent dependence of fluorescence, both fluorescence of them shifted to longer wavelengths as the polarity of the solvent increased. Fluorescence spectra of pyrene derivs. synthesized in this study at satd. concns. in CH2Cl2 exhibited excimer emissions in the longer wavelength regions compared to that of unsubstituted pyrene. Fluorescence quantum yields of silicon analogs were higher than that of the corresponding carbon analogs in both soln. and solid states. From the results of MO calcns., it was clarified that the effects of the substituents at the 1-position on the pyrene ring on the absorption and fluorescence properties can be explained by the properties of the MOs corresponding to the resp. electron transitions.
- 17Shimizu, M.; Tatsumi, H.; Mochida, K.; Hiyama, T. Solid State Structures and Photophysical Properties of (Trimethylsilyl)Methyl-Substituted Anthracenes and Pyrenes. Chem. Commun. 2008, 2134– 2136, DOI: 10.1039/b716770a17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXltFynsLk%253D&md5=a5b4bd9dc9d74487c2d07fedb204b412Solid state structures and photophysical properties of (trimethylsilyl)methyl-substituted anthracenes and pyrenesShimizu, Masaki; Tatsumi, Hironori; Mochida, Kenji; Hiyama, TamejiroChemical Communications (Cambridge, United Kingdom) (2008), (18), 2134-2136CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)(Trimethylsilyl)methyl groups incorporated at 9- and 9,10-positions of anthracenes and at 1,3,6,8-positions of pyrenes were found to orient perpendicular to the arom. frameworks in their crystals and induce red-shift of UV absorption and fluorescence spectra and enhancement of fluorescence quantum yields as compared with the parent hydrocarbons.
- 18Li, J.-J.; Zhang, H.-Y.; Liu, G.; Dai, X.; Chen, L.; Liu, Y. Photocontrolled Light-Harvesting Supramolecular Assembly Based on Aggregation-Induced Excimer Emission. Adv. Optical Mater. 2021, 9, 2001702– 2001708, DOI: 10.1002/adom.20200170218https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXisVert7fO&md5=2ef75625a7e8842752ca5190bcb2490dPhotocontrolled Light-Harvesting Supramolecular Assembly Based on Aggregation-Induced Excimer EmissionLi, Jing-Jing; Zhang, Heng-Yi; Liu, Guoxing; Dai, Xianyin; Chen, Lei; Liu, YuAdvanced Optical Materials (2021), 9 (2), 2001702CODEN: AOMDAX; ISSN:2195-1071. (Wiley-VCH Verlag GmbH & Co. KGaA)Photocontrolled light-harvesting supramol. assembly with aggregation-induced excimer emission is fabricated by polyanionic γ-cyclodextrin (COONa-γ-CD), pyrene deriv. (PYC12), Nile red (NiR), and diarylethene deriv. (DAE) in aq. soln. Benefiting from the COONa-γ-CD-induced aggregation of PYC12, the fluorescence can be modulated from monomeric state to assembled state with a large red-shift around 100 nm, which exhibits aggregation-induced excimer emission enhancement and makes PYC12 a remarkable energy donor. Subsequently, NiR can function as energy acceptor loaded into PYC12/COONa-γ-CD supramol. assembly, and highly efficient energy transfer process occurs from PYC12/COONa-γ-CD to NiR, with energy transfer efficiency up to 83% at donor/acceptor ratio of 160:1. Moreover, multicolor tunable emission can be achieved simply by tuning the molar ratios of donor and acceptor, notably including white-light emission. Interestingly, loading photoresponsive energy acceptor DAE into PYC12/COONa-γ-CD/NiR assembly endows the light-harvesting system with excellent photocontrolled energy transfer, and this process can be efficiently regulated upon distinct light irradn.
- 19Liu, Y.; Liu, H.; Bai, Q.; Du, C.; Shang, A.; Jiang, D.; Tang, X.; Lu, P. Pyrene[4,5-D]Imidazole-Based Derivatives with Hybridized Local and Charge-Transfer State for Highly Efficient Blue and White Organic Light-Emitting Diodes with Low Efficiency Roll-Off. ACS Appl. Mater. Interfaces 2020, 12, 16715– 16725, DOI: 10.1021/acsami.0c0184619https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXkvFyis7w%253D&md5=1b94bf36f72ff52efa10ac9122b96088Pyrene[4,5-d]imidazole-Based Derivatives with Hybridized Local and Charge-Transfer State for Highly Efficient Blue and White Organic Light-Emitting Diodes with Low Efficiency Roll-OffLiu, Yulong; Liu, Hui; Bai, Qing; Du, Chunya; Shang, Anqi; Jiang, Dongyan; Tang, Xiangyang; Lu, PingACS Applied Materials & Interfaces (2020), 12 (14), 16715-16725CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)A family of pyrene[4,5-d]imidazole derivs., PyPA, PyPPA, PyPPAC, and PyPAC, with different excited states are successfully developed. Among them, PyPPA and PyPPAC possess hybridized local and charge-transfer (HLCT) state, endowing them with pure blue fluorescence as well as high quantum yields. The nondoped org. light-emitting diode (OLED) based on PyPPA displays Commission Internationale de L'Eclairage coordinates of (0.14, 0.13) and achieves a max. external quantum efficiency (EQE) of 8.47%, which are among the highest value reported to date for nondoped blue HLCT OLEDs. The nondoped OLED based on PyPPAC exhibits a max. luminance of 50,046 cd m-2 located in the blue region with CIE coordinates of (0.15, 0.21) and an EQE of 6.74% even when the luminance reached over 10,000 cd m-2. In addn., they both reveal ultimate exciton utilizing efficiencies of nearly 100%. The potential of a blue emitter of PyPPA with an HLCT character for application in white OLED (WOLED) is further tested. The efficient two-color hybrid warm WOLED is successfully achieved, which provides the total EQE, power efficiency, and current efficiency of up to 21.19%, 61.46 lm W-1, and 62.13 cd A-1, resp. The nondoped blue OLEDs and hybrid WOLEDs present good color stabilities with low efficiency roll-offs. Our results prove that taking advantage of the HLCT state, nondoped blue OLEDs as well as hybrid WOLEDs with high performance could be realized, which have a promising prospect for the displays and lightings in the future.
- 20Wu, Y.; Li, X.; Zhao, H.; Li, J.; Miao, Y.; Wang, H.; Zhu, F.; Xu, B. Pyrene-Based Hyperbranched Porous Polymers with Doped Ir(Piq)2(acac) Red Emitter for Highly Efficient White Polymer Light-Emitting Diodes. Org. Electron. 2020, 76, 105487– 105495, DOI: 10.1016/j.orgel.2019.10548720https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhvFGms73K&md5=caabf78a73904e6d45133a0e8bb39695Pyrene-based hyperbranched porous polymers with doped Ir(piq)2(acac) red emitter for highly efficient white polymer light-emitting diodesWu, Yuling; Li, Xuefeng; Zhao, Haocheng; Li, Jie; Miao, Yanqin; Wang, Hua; Zhu, Furong; Xu, BingsheOrganic Electronics (2020), 76 (), 105487CODEN: OERLAU; ISSN:1566-1199. (Elsevier B.V.)Here, we designed and prepd. a series of hyperbranched porous polymers constructed using fluorene branches and pyrene core, and all hyperbranched porous polymers exhibit intense blue fluorescence, good morphol. stability, and high thermal stability. Further, it is found that the aperture sizes for hyperbranched porous polymers can be adjusted by simply changing the content of pyrene and fluorene in the synthesis process. When the feed ratios of pyrene in the total polymers is 15 mol%, the optimized aperture size was obtained, which is slightly larger than the maxlength of complementary red emitter Bis(1-phenylisoquinoline)(acetylacetonate)iridium (III) (Ir(piq)2acac), indicating the Ir(piq)2acac can well distributed in the apertures of hyperbranched porous polymers in co-doped film of Ir(piq)2acac and hyperbranched porous polymers. The fabricated polymer-light-emitting diode (PLED) with such co-doped film as light-emitting layer realizes good white emission with almost equal blue and red emission intensity from hyperbranched porous polymers and Ir(piq)2acac. The balanced electroluminescent (EL) spectra contribute to ideal Commission Internationale de l'Eclairage (CIE) coordinate of (0.326, 0.374) located at white light zone. In addn., the device also achieves high device performance with max. luminance and current efficiency reaching 5369 cd/m2 and 8.35 cd/A, resp. We believe that such porous-structure polymers have huge potential applications in the development of highly efficient white PLEDs with reducing prodn. cost.
- 21Kumar, V.; Sk, B.; Kundu, S.; Patra, A. Dynamic and Static Excimer: A Versatile Platform for Single Component White-Light Emission and Chelation-Enhanced Fluorescence. J. Mater. Chem. C 2018, 6, 12086– 12094, DOI: 10.1039/C8TC03035A21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvVOjt7fF&md5=5d2de664f5c65e86468758281aaaae28Dynamic and static excimer: a versatile platform for single component white-light emission and chelation-enhanced fluorescenceKumar, Virendra; Sk, Bahadur; Kundu, Subhankar; Patra, AbhijitJournal of Materials Chemistry C: Materials for Optical and Electronic Devices (2018), 6 (44), 12086-12094CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)The present study demonstrates the tuning of iconic optical features of pyrene through its judicious assembly with a C3-sym. triaminoguanidinium ion, leading to the development of a unique multifunctional luminescent material PYTG. By fine tuning the concn. and the external stimuli, such as temp., the addn. of analytes led to a dramatic change in the fluorescence of PYTG, providing an excellent platform for the exploration of the dynamic and static excimer formation. Recently, white-light-emitting mol. probes have received considerable attention from the scientific community due to their great potentials in display devices. Tripodal PYTG was employed as a pure white-light emitter consisting of blue emission from monomers and orange emission from excimers both in soln. and thin film with Commission Internationale de l'Eclairage (CIE) coordinates of (0.33, 0.34) and (0.33, 0.38), resp. The formation of a dynamic excimer along with monomer fluorescence at higher concns. of PYTG led to tunable emission. Addnl., the rich electronic properties of PYTG allowed efficient detection of trivalent metal ions by turn-on fluorescence and colorimetric sensing of fluoride ions. PYTG selectively detected Fe3+ and Al3+ with nanomolar sensitivity in a semi-aq. soln. via a chelation-enhanced fluorescence response in the orange-red region (λem = 588 nm) by static excimer formation. The 'on-off' fluorescence switching by the consecutive addn. of trivalent cations and a chelating ligand EDTA makes PYTG a promising fluorescent mol. switch. A simple and cost-effective strategy, leading to the development of a versatile fluorescent probe and an in-depth exploration of the structure-property relationship as delineated in the present manuscript, will pave the way for the emergence of novel task-specific mol. optical materials.
- 22Feng, X.; Qi, C.; Feng, H.-T.; Zhao, Z.; Sung, H. H. Y.; Williams, I. D.; Kwok, R. T. K.; Lam, J. W. Y.; Qin, A.; Tang, B. Z. Dual Fluorescence of Tetraphenylethylene-substituted Pyrenes with Aggregation-Induced Emission Characteristics for White-Light Emission. Chem. Sci. 2018, 9, 5679– 5687, DOI: 10.1039/C8SC01709C22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtVGisL7O&md5=1a55a288ea8b7e8b83af7b68dd13b2d8Dual fluorescence of tetraphenylethylene-substituted pyrenes with aggregation-induced emission characteristics for white-light emissionFeng, Xing; Qi, Chunxuan; Feng, Hai-Tao; Zhao, Zheng; Sung, Herman H. Y.; Williams, Ian D.; Kwok, Ryan T. K.; Lam, Jacky W. Y.; Qin, Anjun; Tang, Ben ZhongChemical Science (2018), 9 (25), 5679-5687CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)This article presents a new strategy to achieve white-light emission from single tetraphenylethylene-substituted pyrenes (TPE-Pys) with aggregation-induced emission (AIE) characteristics. TPE-Pys were synthesized by a Pd-catalyzed coupling reaction of a boronic acid or pinacol ester of pyrene and tetraphenylethylene (TPE) derivs. and showed multicolor emission by introducing different substituents on the Ph rings of TPE. TPE-Pys with a TPE unit at the 1-position and asym. TPE units at 2,7-positions show dual fluorescence in THF/water mixts. to realize white-light emission with CIE coordinates of (x = 0.30 and y = 0.41) and (x = 0.21 and y = 0.16), resp. The structure-property relationship of TPE-Pys were investigated to elucidate the origin of the white emission. The results showed that due to the weak electronic interaction of pyrene and its chromophoric units at the 2,7-positions and the constraint of the rotation of the TPE unit at the 1-position of pyrene, each component can exhibit its own emission color. The combination of appropriate colors gives rise to white-light emission. Such a principle of mol. design may open a new avenue for prepg. advanced multicolor and multifunctional optical materials for org. electronics.
- 23You, J.; Li, G.; Wang, R.; Nie, Q.; Wang, Z.; Li, J. Pyrene-Cored Dendrimer with Carbazole Derivatives as Dendrons: Synthesis, Properties and Application in White Light-Emitting Diode. Phys. Chem. Chem. Phys. 2011, 13, 17825– 17830, DOI: 10.1039/c1cp21848d23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXht1eqtb7M&md5=22d5065583a812a27a0dda34cb7c3f7cPyrene-cored dendrimer with carbazole derivatives as dendrons: synthesis, properties and application in white light-emitting diodeYou, Jia; Li, Guiyang; Wang, Renjie; Nie, Qiuping; Wang, Zhonggang; Li, JiuyanPhysical Chemistry Chemical Physics (2011), 13 (39), 17825-17830CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)A new dendrimer using pyrene as core and carbazole deriv. as dendron was successfully prepd. via Suzuki coupling reaction. Its chem. structure was confirmed through 1H NMR, elemental anal. and MALDI-TOF MS methods. The dendrimer synthesized possessed excellent thermal stability with initial decompn. temp. over 470° and high fluorescence quantum yield of 86%. The luminescence spectra showed that, relative to the soln. sample, the emission peaks of the solid dendrimer film were apparently broadened and red-shifted, indicating the strong π-π stacking effect between the pyrene moieties. By doping 1.5% of the dendrimer in 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), a light-emitting diode device was fabricated in the ITO/NPB/NPB : dendrimer (1.5%)/TPBI/Mg : Ag configuration, which emitted a white color with Commission Internationale de L'Eclairage (CIEx,y) coordinates of (0.29, 0.34) and a max. brightness of 1300 cd m-2, exhibiting promising potential in white light-emitting diode application.
- 24Unny, D.; Kandregula, G. R.; Sivanadanam, J.; Ramanujam, K. Molecular Engineering of Pyrene Carbazole Dyes with a Single Bond and Double Bond as the Mode of Linkage. New J. Chem. 2020, 44, 16511– 16525, DOI: 10.1039/D0NJ03228J24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhs1ehurzM&md5=a412c98bffc73b3f154e4fa6d20d8f25Molecular engineering of pyrene carbazole dyes with a single bond and double bond as the mode of linkageUnny, Divya; Kandregula, Ganapathi Rao; Sivanadanam, Jagadeeswari; Ramanujam, KothandaramanNew Journal of Chemistry (2020), 44 (38), 16511-16525CODEN: NJCHE5; ISSN:1144-0546. (Royal Society of Chemistry)Both carbazole and pyrene are electron-rich arom. systems and are expected to be potential donors when used in a push-pull dye architecture in the field of DSSC technol. Herein, two novel pyrene-carbazole dyes bearing single bond (PC1) and double bond (PC2) linkers and cyano-acrylic acid as an acceptor were synthesized. The dye with a double bond spacer (PC2) in the presence of CDCA achieved an improved power conversion efficiency of 6.30% with a short circuit current of 11.59 mA cm-2, open circuit potential (VOC) of 0.80 V, and a fill factor of 0.68 under std. global AM 1.5G solar conditions. Cyclic voltammetry and d. functional theory studies indicate that the incorporation of two donors improved the ease of oxidn. of the dyes, which resulted in a high VOC. Despite having a rigid single bond, the charge transfer of the PC1 dye is found to be poor, which affected the photovoltaic performance. The dihedral angle measured at each joint of the optimized dye indicated that PC2 exhibits excellent intramol. charge transfer due to the near planarity in the structure. Besides, the high electron lifetime in the excited state of PC2 makes it the best performer among the three dyes studied.
- 25Zhao, Z.; Xu, X.; Wang, H.; Lu, P.; Yu, G.; Liu, Y. Zigzag Molecules from Pyrene-Modified Carbazole Oligomers: Synthesis, Characterization, and Application in OLEDs. J. Org. Chem. 2008, 73, 594– 602, DOI: 10.1021/jo702075r25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhsVCrsLvK&md5=5003eede45905eb95877639fc9bb2751Zigzag Molecules from Pyrene-Modified Carbazole Oligomers: Synthesis, Characterization, and Application in OLEDsZhao, Zujin; Xu, Xinjun; Wang, Hongbo; Lu, Ping; Yu, Gui; Liu, YunqiJournal of Organic Chemistry (2008), 73 (2), 594-602CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)A series of monodisperse, pyrene-modified oligocarbazoles was synthesized and fully characterized. Carbazoles were linked by ethynylene through the 3- and 6-positions, forming a zigzag mol. backbone and stable, size-independent absorption, and emission were obsd. from these oligomers in solns. because their conjugation length was confined. Oligomers with pyrene exhibited much higher fluorescence quantum yields than those of oligomers without it. Different positions of pyrene in the oligocarbazole main chain resulted in a remarkable change in absorption and emission spectra. Moreover, devices with four different architectures based on these oligomers were fabricated and investigated. Pyrene-modified carbazole oligomers exhibited bifunctional properties (light-emitting and hole-transport). Moreover, these devices showed moderate performances; for example,the device based on Cz3PyCz3 (I) presented an external quantum efficiency of 0.69% and a max. brightness of 1782 cd/m2 at 13.5 V, which indicated these oligomers were promising optoelec. materials.
- 26Valsange, N. G. A New Pyrene Cored Small Organic Molecule with a Flexible Alkyl Spacer: A Potential Solution Processable Blue Emitter with Bright Photoluminescence. New J. Chem. 2017, 41, 11383– 11390, DOI: 10.1039/C7NJ01921A26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsVejurvM&md5=102a6c8df2cd41facf459d2d8c347c20A new pyrene cored small organic molecule with a flexible alkyl spacer: a potential solution processable blue emitter with bright photoluminescenceValsange, Nitin G.; Wong, F. L.; Shinde, Durgaprasad; Lee, C. S.; Roy, V. A. L.; Manzhos, Sergei; Feron, K.; Chang, Samuel; Katoh, Ryuzi; Sonar, Prashant; Wadgaonkar, Prakash P.New Journal of Chemistry (2017), 41 (19), 11383-11390CODEN: NJCHE5; ISSN:1144-0546. (Royal Society of Chemistry)A new pyrene cored small org. mol. viz. 1,3,6,8-tetrakis(4-((5-(9H-carbazol-9-yl)pentyl)oxy)phenyl)pyrene (PY-II) was designed and synthesized. The carbazole moiety with an alkyl spacer was introduced at 1, 3, 6 and 8 positions of the pyrene core to improve the charge transport properties and soln. processability. PY-II exhibited excellent soly. in common org. solvents and high thermal stability up to 345°. The photoluminescence quantum yield (PLQY) of PY-II in soln. is 0.9 with bright blue emission near 450 nm which is just appropriate for the human eye. The soln. processed non-doped OLED device fabricated using PY-II as an emissive layer afforded a pure blue emission with CIE coordinates of 0.16 and 0.16, a power efficiency of 0.17 lm W-1, a max. current efficiency of 0.41 cd A-1 and a max. brightness of 202 cd m-2.
- 27Kotchapradist, P.; Prachumrak, N.; Tarsang, R.; Jungsuttiwong, S.; Keawin, T.; Sudyoadsuk, T.; Promarak, V. Pyrene-Functionalized Carbazole Derivatives as Non-Doped Blue Emitters for Highly Efficient Blue Organic Light-Emitting Diodes. J. Mater. Chem. C 2013, 1, 4916– 4924, DOI: 10.1039/c3tc30719k27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFKns77F&md5=aab2ba25107f379cec983accbb0be414Pyrene-functionalized carbazole derivatives as non-doped blue emitters for highly efficient blue organic light-emitting diodesKotchapradist, Palita; Prachumrak, Narid; Tarsang, Ruangchai; Jungsuttiwong, Siriporn; Keawin, Tinnagon; Sudyoadsuk, Taweesak; Promarak, VinichJournal of Materials Chemistry C: Materials for Optical and Electronic Devices (2013), 1 (32), 4916-4924CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)Pyrene-functionalized carbazole derivs., N-dodecyl-3,6-di(pyren-1-yl)carbazole (CP2), N-dodecyl-1,3,6-tri(pyren-1-yl)carbazole (CP3) and N-dodecyl-1,3,6,8-tetra(pyren-1-yl)carbazole (CP4), are synthesized and characterized as simple nondoped soln. processed blue emitters for OLEDs. By multiple substitution of pyrene on the carbazole ring, the authors are able to retain the high blue emissive ability of pyrene in the solid as well as improve the amorphous stability and soly. of the material. These materials show high soln. fluorescence quantum efficiencies (up to 94%) and can form morphol. stable amorphous thin films with Tg ≤ 170°. Soln. processed double-layer OLEDs using these materials as nondoped blue emitters exhibit good device performance with luminance efficiencies up to 2.53 cd A-1. Their multi-layer devices exhibit outstanding performances. The CP2-based device shows a low turn-on voltage (down to 2.6 V) with an excellent blue emission color (λem = 436 nm) and CIE coordinates of (0.16, 0.14), while the CP3 and CP4-based blue devices also display low turn-on voltages (down to 2.7 V) with high luminance (up to 24479 cd m-2) and luminance efficiencies (up to 6.92 cd A-1).
- 28Kaafarani, B. R. Bis(Tercarbazole) Pyrene and Tetrahydropyrene Derivatives: Photophysical and Electrochemical Properties, Theoretical Modeling, and OLEDs. J. Mater. Chem. C 2019, 7, 5009– 5018, DOI: 10.1039/C8TC06266H28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXlsFeqtr0%253D&md5=201753419955731a6b96bb9b2069dce9Bis(tercarbazole) pyrene and tetrahydropyrene derivatives: photophysical and electrochemical properties, theoretical modeling, and OLEDsKaafarani, Bilal R.; El-Assaad, Tarek H.; Smith, William A.; Ryno, Sean M.; Hermerschmidt, Felix; Lyons, Jeffrey; Patra, Digambara; Wex, Brigitte; List-Kratochvil, Emil J. W.; Risko, Chad; Barlow, Stephen; Marder, Seth R.Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2019), 7 (17), 5009-5018CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)2,7-Bis(3,3'',6,6''-tetra(tert-butyl)-9'H-9,3':6',9''-tercarbazol-9-yl)-4,5,9,10-tetrahydropyrene I and 2,7-bis(3,3'',6,6''-tetra(tert-butyl)-9'H-9,3':6',9''-tercarbazol-9-yl)pyrene II, along with a model compd., 3,3'',6,6''-tetra(tert-butyl)-9'-(4-(tert-butyl)phenyl)-9'H-9,3':6',9''-tercarbazole III, were synthesized using microwave-assisted palladium-catalyzed coupling and compared to analogous 3,6-di(tert-butyl)carbazol-9-yl species. Time-dependent d. functional theory (TDDFT) calcns. revealed absorption with quadrupolar (ter)carbazole-to-bridge CT character. Compd. II was unusual in showing dual fluorescence in a no. of solvents; the longer wavelength feature of which was markedly more solvatochromic than the bands of other compds. Following the obsd. three oxidns. on TCz model compd. III, compds. I and II could be electrochem. reversibly oxidized to hexacations with four oxidn. and three oxidn. steps in a 2 : 2 : 1 : 1 and a 2 : 2 : 2 current ratio, resp. Tercarbazole derivs. I and II had been used as the emissive layers of simple soln.-processed few-layer org. light-emitting diodes.
- 29Joseph, V.; Thomas, K. R. J.; Sahoo, S.; Singh, M.; Jou, J.-H. Cyano-Functionalized Carbazole Substituted Pyrene Derivatives for Promising Organic Light-Emitting Diodes. Dyes Pigm. 2018, 158, 295– 305, DOI: 10.1016/j.dyepig.2018.05.03829https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtVKrsbjJ&md5=abfe27712d29ce2ebee7b709a1516db9Cyano-functionalized carbazole substituted pyrene derivatives for promising organic light-emitting diodesJoseph, Vellaichamy; Thomas, K. R. Justin; Sahoo, Snehasis; Singh, Meenu; Jou, Jwo-HueiDyes and Pigments (2018), 158 (), 295-305CODEN: DYPIDX; ISSN:0143-7208. (Elsevier Ltd.)Balanced charge transport is crucial to realize efficient org. light-emitting diodes. In this work, pyrene derivs. featuring variable no. of cyano-functionalized carbazoles are synthesized and characterized by photophys., electrochem., thermal and electroluminescence studies. The compds. displayed progressive variation in absorption and emission wavelength reflecting the effect of chromophore loading. The electroluminescence color change from deep blue to green on varying the no./position of cyanocarbazole units on pyrene. 1,6-Disubstituted deriv. exhibited blue shift in absorption and emission when compared to the 1,8-analog. The current efficiency and power efficiency of the devices progressively increase on increasing the cyanocarbazole load on pyrene. It is probably originating from the balanced charge transport due to the increase in the no. of cyanocarbazole units on pyrene and effective harvest of excitons in emissive layer. The best electroluminescence performance of the doped device fabricated from tetra-substituted deriv. (1 wt%) displayed relatively high power efficiency (5.8 lm/W) and current efficiency (9.2 cd/A).
- 30Zhang, T.; Ye, J.; Luo, A.; Liu, D. Efficient Deep Blue Emitter Based on Carbazole-Pyrene Hybrid for Non-Doped Electroluminescent Device. Opt. Mater. 2020, 100, 109632– 109637, DOI: 10.1016/j.optmat.2019.10963230https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlWjtw%253D%253D&md5=ee659aadc3a499b771c87745e189caa4Efficient deep blue emitter based on carbazole-pyrene hybrid for non-doped electroluminescent deviceZhang, Ting; Ye, Jieyang; Luo, Ansheng; Liu, DiOptical Materials (Amsterdam, Netherlands) (2020), 100 (), 109632CODEN: OMATET; ISSN:0925-3467. (Elsevier B.V.)A new deep blue fluorescent material based on carbazole-pyrene hybrid, namely PyEtCz, was synthesized by palladium catalyzed C-C Suzuki coupling reaction, and structurally characterized by NMR, mass spectra and elemental anal. The thermal stability, photophys. and optoelectronic properties were fully investigated. The material shows good thermal stability and can form an amorphous glass state. Its CH2Cl2 soln. exhibits strong deep-blue emission with high fluorescent quantum yield of 75%. PyEtCz also possesses high HOMO level of -5.48 eV that would facilitate efficient hole injection into the emitting layer. The non-doped OLED using PyEtCz as emitter through vacuum evapn. was fabricated for purpose of investigating its electroluminescence properties. The device exhibited stable blue electroluminescence with CIE coordinate of (0.15, 0.10), a good performance with max. luminance of 6573 cd m-2 and max. luminance efficiency of 3.24 cd A-1 (3.35%) was achieved.
- 31Rachuta, K.; Bayda, M.; Majchrzak, M.; Koput, J.; Marciniak, B. Unusual Emission Properties of the Selected Organosilicon Compounds Containing a Styryl-Carbazole Chromophore: Inversion of the Singlet Excited States. Phys. Chem. Chem. Phys. 2017, 19, 11698– 11705, DOI: 10.1039/C7CP01292F31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXlslCrt70%253D&md5=0971f6a4aaf51a54f20b1b7e09a5cfd7Unusual emission properties of the selected organosilicon compounds containing a styryl-carbazole chromophore: inversion of the singlet excited statesRachuta, K.; Bayda, M.; Majchrzak, M.; Koput, J.; Marciniak, B.Physical Chemistry Chemical Physics (2017), 19 (18), 11698-11705CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)The spectroscopic and photophys. properties of silicon-contg. styryl-carbazole were investigated in various solvents, and the results were analyzed with ref. to its carbon derivs. In n-hexane, both the silicon- and the carbon-contg. compds. had very similar emission properties. In acetonitrile, the emission properties remained the same for the C-compd. but changed significantly for the Si-compds. In particular, the fluorescence spectra of the latter were red-shifted, and their radiative rate consts. were even 7 times larger than in n-hexane, which suggested that the emissive states of the silicon-contg. compds. were different in these two solvents. DFT calcns. using the CAM-B3LYP functional showed that the emissive state of the C-compd. involves the LUMO+1 orbital regardless of the medium. In contrast, for the Si-compd., changing the medium from n-hexane to acetonitrile resulted in the inversion of the emissive states from an excited state involving the LUMO+1 orbital (the dipole moment μ = 4.2 D) to an excited state involving the LUMO orbital (μ = 8.9 D).
- 32Eaton, D. F. Reference Materials for Fluorescence Measurement. Pure Appl. Chem. 1988, 60, 1107– 1114, DOI: 10.1351/pac19886007110732https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1cXlsFyrtL0%253D&md5=51ba5738e8da49584e6393251022a47fReference materials for fluorescence measurementEaton, David F.Pure and Applied Chemistry (1988), 60 (7), 1107-14CODEN: PACHAS; ISSN:0033-4545.A review with 19 refs. is given on std. practices and materials for fluorescence measurements and the avoidance of exptl. inadequacies attendant on their application in practical use. Appropriate methods are discussed which strike a balance between ease of application, generality of use, and reliability.
- 33Rachuta, K.; Bayda-Smykaj, M.; Majchrzak, M.; Koput, J.; Marciniak, B. Emission Properties of Si-Based Styryl-Carbazole Derivatives: Role of Meta- and Para-Vinyl Substituents and Silicon Atom. J. Lumin. 2018, 196, 57– 63, DOI: 10.1016/j.jlumin.2017.12.00733https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvF2ntr3P&md5=2fb4e18a07b8e68a40385c11831294fdEmission properties of Si-based styryl-carbazole derivatives: Role of meta- and para-vinyl substituents and silicon atomRachuta, K.; Bayda-Smykaj, M.; Majchrzak, M.; Koput, J.; Marciniak, B.Journal of Luminescence (2018), 196 (), 57-63CODEN: JLUMA8; ISSN:0022-2313. (Elsevier B.V.)A series of styryl-carbazole derivs. (with and without a silicon atom) were investigated in n-hexane and in acetonitrile in terms of their spectroscopic and photophys. properties. The major question addressed in this work is how the presence of a trimethylsilyl group modifies the absorption and emission properties of styryl-carbazoles depending whether vinyl groups are in a meta- or para- position. It was obsd. that only para-styryl-carbazole contg. silicon undergoes a solvent-induced inversion of its lowest singlet excited states whereas meta-styryl-carbazole contg. silicon retains the properties of the meta-styryl-carbazole itself. The different character of the emissive state was deduced from its 7-fold larger radiative rate const. in acetonitrile compared to results in n-hexane. DFT calcns. revealed on the mol. level why inversion of the excited states occurs only for this silicon-based styryl-carbazole whose vinyl group is in the para- and not in the meta- position.
- 34Berlman, I. B., Handbook of Florescence Spectra of Aromatic Molecules; Academic Press: New York and London, 1971.There is no corresponding record for this reference.
- 35Parker, C. A.; Hatchard, C. G. Delayed Fluorescence of Pyrene in Ethanol. Trans. Faraday Soc. 1963, 59, 284– 295, DOI: 10.1039/tf963590028435https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF3sXktVKls7Y%253D&md5=c3177bd5359a90bcd16337cd7bbda394Delayed fluorescence of pyrene in ethanolParker, C. A.; Hatchard, C. G.Transactions of the Faraday Society (1963), 59 (), 284-95CODEN: TFSOA4; ISSN:0014-7672.cf. CA 55, 19879f. Normal and delayed fluorescence at room temp. showed bands due to singlet excited monomer and excited dimer. At low pyrene concn. the relative intensity of the normal fluorescence of the dimer tends to zero, but the relative intensity of the delayed fluorescence of the dimer was almost const. The intensity of delayed fluorescence of both monomer and dimer was proportional to the sq. of the rate of absorption of exciting light. The delayed fluorescence was due to triplet-triplet quenching which resulted in the formation of excited dimer mols., some of which fluoresce and some of which dissoc. into excited and ground-state singlet mols. The delayed fluorescence of anthracene and phenanthrene solns. has the same mechanism.
- 36Sun, Y.-P.; Sears, J.; D. F; Saltiel, J. Three-Component Self-Modeling Technique Applied to Luminescence Spectra. Anal. Chem. 1987, 59, 2515– 2519, DOI: 10.1021/ac00147a01536https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2sXlsVCju7w%253D&md5=81269f70235a229572134af4d7dd7be0Three-component self-modeling technique applied to luminescence spectraSun, Ya Ping; Sears, Donald F., Jr.; Saltiel, JackAnalytical Chemistry (1987), 59 (20), 2515-19CODEN: ANCHAM; ISSN:0003-2700.The selection of pure component spectral coeffs. was improved when addnl. applicable constraints were imposed. The method was demonstrated for a 2-component system (the phosphorescence and delayed fluorescence of benzophenone) and extended to 3 components. It succeeded in reproducing theor. curves used to construct an artificial 3-component input matrix, and it was applied to resolve exptl. spectra composed of the fluorescence of 2 conformers of trans-1,2-di-2-naphthylethene and a background spectrum dominated by Raman emission at the excitation wavelength region.
- 37Catalán, J.; Zimányi, L.; Saltiel, J. Medium Controlled Aggregation of Trans Stilbene. J. Am. Chem. Soc. 2000, 122, 2377– 2378, DOI: 10.1021/ja991834o37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXhtlKjsLc%253D&md5=dc78333d6c6f832079c61c90d018981bMedium-Controlled Aggregation of trans-StilbeneCatalan, Javier; Zimanyi, Laszlo; Saltiel, JackJournal of the American Chemical Society (2000), 122 (10), 2377-2378CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)UV and fluorescence spectra of trans-stilbene solns. in isopentane at low temps. (98-110 K) undergo changes indicative of face to edge monomer assocn. A model based on rate detg. photodimerization and dimer monomer assocn. to trimer is discussed.
- 38Zimányi, L.; Kulcsár, Á.; Lanyi, J. K.; Sears, J.; D. F; Saltiel, J. Singular Value Decomposition with Self-Modeling Applied to Determine Bacteriorhodopsin Intermediate Spectra. Analysis of Simulated Data. Proc. Natl. Acad. Sci. U. S. A. 1999, 96, 4408– 4413, DOI: 10.1073/pnas.96.8.440838https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXjs1ylsrg%253D&md5=3d547b26bf19c0ea26f0d676c7f78426Singular value decomposition with self-modeling applied to determine bacteriorhodopsin intermediate spectra: analysis of simulated dataZimanyi, Laszlo; Kulcsar, Agnes; Lanyi, Janos K.; Sears, Donald F., Jr.; Saltiel, JackProceedings of the National Academy of Sciences of the United States of America (1999), 96 (8), 4408-4413CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)An a priori model-independent method for the detn. of accurate spectra of photocycle intermediates is developed. The method, singular value decompn. with self-modeling (SVD-SM), is tested on simulated difference spectra designed to mimic the photocycle of the Asp-96 → Asn mutant of bacteriorhodopsin. Stoichiometric constraints, valid until the onset of the recovery of bleached bacteriorhodopsin at the end of the photocycle, guide the self-modeling procedure. The difference spectra of the intermediates are detd. in eigenvector space by confining the search for their coordinates to a stoichiometric plane. In the absence of random noise, SVD-SM recovers the intermediate spectra and their time evolution nearly exactly. The recovery of input spectra and kinetics is excellent although somewhat less exact when realistic random noise is included in the input spectra. The difference between recovered and input kinetics is now visually discernible, but the same reaction scheme with nearly identical rate consts. to those assumed in the simulation fits the output kinetics well. SVD-SM relegates the selection of a photocycle model to the late stage of the anal. In thus avoids derivation of erroneous model-specific spectra that result from global model-fitting approaches that assume a model at the outset.
- 39Liu, K.-L.; Lee, S.-J.; Chen, I.-C.; Hsu, C.-P.; Yeh, M.-Y.; Luh, T.-Y. Ultrafast Energy Transfer in a Regioregular Silylene-Spaced Copolymer. J. Phys. Chem. C 2010, 114, 13909– 13916, DOI: 10.1021/jp102376x39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXpsVKksL0%253D&md5=a4db845332d50fb4900afb2eec52fd47Ultrafast Energy Transfer in a Regioregular Silylene-Spaced CopolymerLiu, Kuan-Lin; Lee, Sheng-Jui; Chen, I.-Chia; Hsu, Chao-Ping; Yeh, Mei-Yu; Luh, Tien-YauJournal of Physical Chemistry C (2010), 114 (32), 13909-13916CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)The energy-transfer properties of a regioregular silylene-spaced alternating donor-acceptor copolymer (donor-SiMe2-acceptor-SiMe2)m are detd. with time-resolved spectroscopy; 4,4'-divinylbiphenyl serves as donor and 4,4'-divinylstilbene as acceptor. Steady-state fluorescence spectra show that the energy transfer is efficient. With excitation at 266 nm, fluorescence up-conversion curves at various detection wavelengths are measured to explore the detailed dynamics of the energy transfer. A rate ∼(0.3 ps)-1 for energy transfer between the S1 states of the donor and acceptor moieties is obsd. Theor. calcns. based on fragment excitation difference provide a rate of energy transfer near the exptl. value with detailed insight into the mechanism of energy transfer. The results of theor. calcns. indicate that the Coulomb interaction is dominant and the Dexter process is weak. The high-multipole interactions are important for energy transfer.
- 40Lakowicz, J. R., Principles of Fluorescence Spectroscopy; Kluwer Academik/Plenum Publisher: New York, 1999.There is no corresponding record for this reference.
- 41Yoshihara, T.; Druzhinin, S. I.; Demeter, A.; Kocher, N.; Stalke, D.; Zachariasse, K. A. Kinetics of Intramolecular Charge Transfer with N-Phenylpyrrole in Alkyl Cyanides. J. Phys. Chem. A 2005, 109, 1497– 1509, DOI: 10.1021/jp046586j41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXhtVKlt7k%253D&md5=39507e9af3bc82d5e10ef0908e62088dKinetics of Intramolecular Charge Transfer with N-Phenylpyrrole in Alkyl CyanidesYoshihara, Toshitada; Druzhinin, Sergey I.; Demeter, Attila; Kocher, Nikolaus; Stalke, Dietmar; Zachariasse, Klaas A.Journal of Physical Chemistry A (2005), 109 (8), 1497-1509CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)For the electron acceptor/donor mol. N-phenylpyrrole (PP), the fast intramol. charge transfer (ICT) reaction accompanied by dual fluorescence from a locally excited (LE) and an ICT state is investigated in alkyl cyanide solvents as a function of temp. After a comparison of the x-ray crystal structure of PP with calcns. from the literature, absorption and fluorescence spectra of PP in a series of solvents over a wide polarity range are discussed. ICT with PP strongly depends on solvent polarity and starts to appear in solvents more polar than di-Et ether. From an anal. of the ICT/LE fluorescence quantum yield ratio Φ'(ICT)/Φ(LE), approx. data for the change in enthalpy -ΔH of the ICT reaction of PP are obtained, ranging from 9 kJ/mol in acetonitrile to 4 kJ/mol in Bu cyanide. From ICT and LE fluorescence decays of PP measured as a function of temp., the forward (Ea = 9 kJ/mol in Et cyanide (EtCN) and 6 kJ/mol in MeCN) and backward (Ed = 16 kJ/mol in EtCN and MeCN) ICT reaction barriers are detd. From these data, -ΔH (7 kJ/mol (EtCN); 10 kJ/mol (MeCN)) is calcd., in good agreement with the results coming from Φ'(ICT)/Φ(LE). The data for Ea show that the forward ICT barrier becomes smaller with increasing solvent polarity, whereas the absence of change for Ed comes from the compensating increase of -ΔH. Both observations are indicative of a late transition state for the LE → ICT reaction. For PP in EtCN and MeCN, the ICT radiative rate const. k'f(ICT) increases with temp. This is caused by the ICT low transition dipole moment and hence does not contain information on the mol. structure (twisted or planar) of the ICT state. The fast ICT obsd. with PP supports our previous conclusion, based on a comparison of PP with its planarized deriv. fluorazene, that the pyrrole and Ph moieties in the ICT state of PP are coplanar and possess substantial electronic coupling.
- 42Bayda, M.; Angulo, G.; Hug, G. L.; Ludwiczak, M.; Karolczak, J.; Koput, J.; Dobkowski, J.; Marciniak, B. Electron Transfer in Silicon-Bridged Adjacent Chromophores: The Source for Blue-Green Emission. Phys. Chem. Chem. Phys. 2017, 19, 11404– 11415, DOI: 10.1039/C7CP00590C42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXlsVars74%253D&md5=3b1710da709ca08e1f61d0c41265f5f0Electron transfer in silicon-bridged adjacent chromophores: the source for blue-green emissionBayda, Malgorzata; Angulo, Gonzalo; Hug, Gordon L.; Ludwiczak, Monika; Karolczak, Jerzy; Koput, Jacek; Dobkowski, Jacek; Marciniak, BronislawPhysical Chemistry Chemical Physics (2017), 19 (18), 11404-11415CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Si-Bridged chromophores were proposed as sources for blue-green emission in several technol. applications. The origin of this dual emission is to be found in an internal charge transfer reaction. The current work is an attempt to describe the details of these processes in these kinds of substances, and to design a mol. architecture to improve their performance. Nuclear motions essential for intramol. charge transfer (ICT) can involve processes from twisted internal moieties to dielec. relaxation of the solvent. To address these issues, the authors studied ICT between adjacent chromophores in a mol. compd. contg. N-isopropylcarbazole (CBL) and 1,4-divinylbenzene (DVB) linked by a dimethylsilylene bridge. In nonpolar solvents emission arises from the local excited state (LE) of carbazole whereas in solvents of higher polarity dual emission was detected (LE + ICT). The CT character of the addnl. emission band was concluded from the linear dependence of the fluorescence maxima on solvent polarity. Electron transfer from CBL to DVB resulted in a large excited-state dipole moment (37.3 D) as detd. from a solvatochromic plot and DFT calcns. Steady-state and picosecond time-resolved fluorescence expts. in butyronitrile (293-173 K) showed that the ICT excited state arises from the LE state of carbazole. These results were analyzed and are in accordance with an adiabatic version of Marcus theory including solvent relaxation.
Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpcc.1c00990.
Synthesis procedures and methods used, calculated ΔGel and ΔGHT, absorption and emission properties (λAbs, max, λf, max, τs, and Φf), and kinetic equations derived for CT1 and CT2 (PDF)
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