Regioselective Hydrogenation of a 60-Carbon Nanographene Molecule toward a Circumbiphenyl Core
- Xuelin YaoXuelin YaoMax Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, GermanyMore by Xuelin Yao,
- Xiao-Ye WangXiao-Ye WangMax Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, GermanyMore by Xiao-Ye Wang,
- Christopher SimpsonChristopher SimpsonMax Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, GermanyMore by Christopher Simpson,
- Giuseppe M. PaternòGiuseppe M. PaternòIstituto Italiano di Tecnologia, Center for Nano Science and Technology, 20133 Milano, ItalyMore by Giuseppe M. Paternò,
- Michele GuizzardiMichele GuizzardiIFN-CNR, Department of Physics, Politecnico di Milano, 20133 Milano, ItalyMore by Michele Guizzardi,
- Manfred WagnerManfred WagnerMax Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, GermanyMore by Manfred Wagner,
- Giulio CerulloGiulio CerulloIFN-CNR, Department of Physics, Politecnico di Milano, 20133 Milano, ItalyMore by Giulio Cerullo,
- Francesco ScotognellaFrancesco ScotognellaIstituto Italiano di Tecnologia, Center for Nano Science and Technology, 20133 Milano, ItalyIFN-CNR, Department of Physics, Politecnico di Milano, 20133 Milano, ItalyMore by Francesco Scotognella,
- Mark D. WatsonMark D. WatsonDepartment of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, United StatesMore by Mark D. Watson,
- Akimitsu Narita*Akimitsu Narita*[email protected]Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, GermanyOrganic and Carbon Nanomaterials Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, JapanMore by Akimitsu Narita, and
- Klaus Müllen*Klaus Müllen*[email protected]Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, GermanyInstitute of Physical Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, GermanyMore by Klaus Müllen
Copyright © 2019 American Chemical Society
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Abstract
Regioselective peripheral hydrogenation of a nanographene molecule with 60 contiguous sp2 carbons provides unprecedented access to peralkylated circumbiphenyl (1). Conversion to the circumbiphenyl core structure was unambiguously validated by MALDI-TOF mass spectrometry, NMR, FT-IR, and Raman spectroscopy. UV–vis absorption spectra and DFT calculations demonstrated the significant change of the optoelectronic properties upon peripheral hydrogenation. Stimulated emission from 1, observed via ultrafast transient absorption measurements, indicates potential as an optical gain material.
Large polycyclic aromatic hydrocarbons (PAHs), (1) i.e., with size >1 nm, can be regarded as nanographene molecules, and have attracted attention for their unique optical, electronic, and magnetic properties. (2) These properties are critically dependent on their aromatic core structure, motivating development of novel synthetic pathways to a variety of distinct aromatic frameworks. (3) Conventional synthetic strategies toward nanographene molecules are mostly based on π-expansion, mainly through planarization of tailor-made oligoarylene precursors, e.g., by oxidative cyclodehydrogenation, (4) photochemical cyclization, (5) and/or flash vacuum pyrolysis. (6) π-expansion of smaller PAH structures also provides access to larger PAHs, for example through Diels–Alder cycloaddition (7) or a sequence of arylation and cyclization at the periphery. (8)
Alternatively, it is possible to modify the aromatic structures of PAHs by “shrinking” the π-conjugated cores, for example through peripheral hydrogenation. We have previously reported that peripheral hydrogenation of hexa-peri-hexabenzocoronene (HBC) selectively leads to peralkylated coronenes. (9) More recently, Shionoya et al. described a catalytic reductive C–C bond cleavage of a corannulene derivative, leading to a benzo[ghi]fluoranthene structure. (10) On the other hand, “π-truncation” of aromatic structures has been applied to fullerene, with the formation of a hoop-shaped cyclic benzenoid compound by Nakamura et al. as one of the most elegant examples. (11) Nevertheless, compared with the π-expansion procedure, the “π-truncation” strategy is underdeveloped. We have been particularly interested in peripheral hydrogenation to produce new PAH or nanographene structures other than known skeletons such as coronene. However, hydrogenation of nanographene molecules larger than HBC has remained elusive.
Circumbiphenyl (2) is a PAH consisting of a biphenyl core encircled by an annulene ring (Figure 1). The parent 2 was accidentally obtained by E. Clar nearly half a century ago during his attempts to synthesize tetrabenzoperopyrene by reductive condensation of naphthanthrone (3). (12) However, this first reported synthetic approach yielded a complex mixture and required multistep separation processes to isolate 2. In 2013, Nuckolls et al. reported a synthesis of a contorted octabenzocircumbiphenyl. (13) However, a straightforward and efficient synthesis of the pristine aromatic structure of circumbiphenyl has never been achieved.
Figure 1
Figure 1. “π-Expansion” toward circumbiphenyl 2 by E. Clar and the postsynthetic “π-truncation” to peralkylated circumbiphenyl 1.
Herein, we report an efficient synthesis of peralkylated circumbiphenyl 1 through “π-truncation”, namely by regioselective hydrogenation of a nanographene molecule 4 with 60 sp2 carbons (Figure 1). Standard spectroscopic characterization corroborates the successful formation of the circumbiphenyl core. UV–vis absorption spectroscopy combined with DFT calculations demonstrate the modulating effect of peripheral hydrogenation on electronic properties, while ultrafast spectroscopy highlights the presence of optical gain. This work offers possibilities not only for acquiring new or unobtainable aromatic structures but also for tuning (opto-)electronic properties of PAHs.
The synthesis of peralkylated circumbiphenyl 1 is outlined in Figure 1. The hydrogenation of nanographene molecule 4, which was prepared following reported procedures, (14) was carried out with Pd/C in dry tetrahydrofuran (THF). The reaction mixture was pressurized to 150 bar H2 and stirred at 120 °C in an autoclave for 1 week to complete the reaction. At a lower pressure of 120 bar and the same temperature of 120 °C, the hydrogenation needed 2 weeks for completion. These conditions are indeed much harsher than those used for the previous hydrogenation of HBC with six dodecyl chains (55–65 bar, 60 °C, 12 h). (9) After cooling, the catalyst was removed by passing through a short pad of silica gel with THF as eluent, and the crude product was obtained as yellowish brown powder in 30% yield.
High-resolution MALDI-TOF MS analyses of 4 and the hydrogenation product revealed exact mass of m/z = 1414.9216 and 1437.0945, respectively, in agreement with the formation of 1 (C108H140) possessing 22 more hydrogen atoms than 4 (C108H118) (Figure 2). The isotopic distribution observed for 1 perfectly matched the simulated pattern, validating the successful hydrogenation of 4. Compound 1 was soluble even in n-hexane (0.65 mg/mL), in which 4 showed little solubility. Both the room-temperature and high-temperature 1H NMR spectra of 1 revealed the disappearance of signals from protons attached to aromatic systems and appearance of new signals in the aliphatic region, indicating the peripheral hydrogenation of 4. 2D NMR analyses of 1 could distinguish different aliphatic proton signals originating from > CH–, −CH2– and −CH3 (NMR spectra see Figures S1–S6 in the Supporting Information). However, accurate assignment of each proton signal of 1 was hampered by the existence of multiple diastereotopic peripheral protons and 1H signal overlap. Compound 1 might consist of multiple stereoisomers, depending on the relative orientations of the four alkyl chains, which is under further investigation in our laboratory.
Figure 2
Figure 2. High-resolution MALDI-TOF MS spectrum of 1 and 4 (inset: the corresponding experimental and simulated isotopic distributions of 1).
FT-IR spectroscopic analysis of 1 and 4 demonstrates the disappearance of aromatic C–H stretching bands at around 3073 cm–1, (15) as well as the fingerprint aromatic C–H bending bands between 730 and 860 cm–1, corroborating peripheral hydrogenation (Figure 3, for full spectra, see Figure S7). Additionally, appearance of bands at 1080 and 465 cm–1 from the saturated C–C stretching vibrations and out-of-plane bending, respectively, verifies the hydrogenated periphery of 1. (16) In Raman spectra (Figure S8), the ratios between D and G bands, I(D)/I(G) for 4 and 1 are 0.50 and 0.56, respectively, in accordance with the fact that I(D)/I(G) varies inversely with the extension of the π-conjugation. (17)
Figure 3
Figure 3. Representative FTIR spectra regions of 1 (blue line) and 4 (red line) measured on powder samples.
In contrast to the broad optical spectra of 4, which could be ascribed to the presence of aggregates, (18) those of 1 (THF solution, see Figure 4a) reveal well-resolved vibronic structures, indicating a significant improvement of solubility after peripheral hydrogenation, suppressing the aggregation. (19) The absorption maximum of 1 (λmax = 381 nm) exhibits a significant blue-shift with respect to 4 (λmax = 411 nm), indicating truncation of the π-skeleton. Notably, the absorption profile of peralkylated circumbiphenyl 1 perfectly matches that of the parent circumbiphenyl 2 (absorption maximum: 364 nm) reported by E. Clar, (12) with a red-shift of the absorption maximum by 17 nm. Peralkylated circumbiphenyl 1 displays a green fluorescence with the emission maximum at 512 nm. The fluorescence quantum yield ΦF of 1 was measured as 12% using 9,10-diphenylanyhracene (in toluene under air, ΦF: 70%) as reference. (20) Compound 4 exhibits a broad fluorescence peaking at 700 nm. The broad peak originates from aggregation, as revealed by concentration-dependent fluorescence studies, whereas the emission maximum of the monomer is at 555 nm (Figure S9). The weak fluorescence of 4 hindered the determination of its fluorescence quantum yield.
Figure 4
Figure 4. (a) Normalized UV–vis absorption and fluorescence spectra (excited at the absorption maxima) of 1 and 4 in THF solution (2 × 10–5 M) (inset: emission of 1 and 4 under 365 nm wavelength of UV lamp). (b) Frontier molecular orbitals and energy diagrams of 1, 2 and 4 at the B3LYP/6-311G(d) level. For simplicity of computation, dodecyl chains of 1 and 4 were removed.
DFT calculations were performed to compare the electronic properties of pristine 4, peripheral hydrogenated 1 and parent circumbiphenyl 2 (Figure 4b). The HOMO and LUMO energy levels of 4 are calculated to be −5.18 and −2.27 eV, respectively, with a HOMO–LUMO gap of 2.91 eV. Peripheral hydrogenation results in a higher lying HOMO (−4.78 eV) and LUMO energy levels (−1.61 eV) of 1, with an energy gap of 3.17 eV which is by 0.26 eV greater than that of 4. These observations are in accordance with the UV–vis experiment, indicating the ability of electronic tuning of PAHs through peripheral hydrogenation. Besides, the DFT-calculated HOMO and LUMO of peralkylated circumbiphenyl 1 reveal the same orbital distribution pattern as that of 2. In addition, the HOMO–LUMO gap of 1 is smaller than that of 2 (3.32 eV), in line with the red-shifted onset of absorption of 1.
Ultrafast transient absorption (TA) spectroscopy (see the Supporting Information) discloses the effect of peripheral hydrogenation on the excited state photodynamics of the molecules. Figure 5 presents the TA spectra for 1 and 4 excited at the low-energy absorption edge (470 nm). Interestingly, whereas for 4 we can distinguish two photobleaching (PB) peaks (500 and 530 nm) and a broad photoinduced absorption (PA) from 600 to 750 nm, 1 exhibits a sharp positive band at 500 nm that can be attributed to stimulated emission (SE), as it overlaps with one of the multiple well-resolved fluorescence peaks and cannot be connected to ground state absorption. Note that the other potential SE signals (550 and 600 nm) are overlapped with the strong and broad PA in the midvisible, which is typical for conjugated systems. (21) The reason why 1 displays SE likely lies in its improved solubility brought about by selective peripheral substitution, as we have recently reported that intermolecular interactions in nanographenes lead to the formation of aggregates with charge-transfer character, in which charge generation quenches SE and gain. (22) The TA dynamics (probe at 500 nm, Figure 5b) show a longer lifetime for 1 (τ1 = 0.4 ± 0.04 ps; τ2 = 420 ± 20 ps) than 4 (τ1 = 0.1 ± 0.01 ps ; τ2 = 120 ± 15 ps), a result that can also correlate with the poorer solubility of 4 with respect to the hydrogenated molecule. In general, these findings highlight the potential of peralkylated circumbiphenyl 1 for applications in photonics and optoelectronics.
Figure 5
Figure 5. (a) Femtosecond transient absorption spectra of 1 and 4 in THF solution at 1 fs pump–probe delay obtained by exciting at 470 nm and probing with a broadband probe light. (b) Transient dynamics for 1 and 4 at a probe wavelength of 500 nm. The solid blue and red lines represent the biexponential best-fit curves for 1 and 4, respectively.
In summary, we have presented hydrogenation as a “π-truncation” strategy leading to the first peralkylated circumbiphneyl 1. MALDI-TOF MS, 1D and 2D NMR combined with FT-IR and Raman results provided an explicit structure proof of the regiospecific peripheral hydrogenation of nanographene molecule 4, leading to a peralkylated circumbiphenyl core. Moreover, investigation of 1 by ultrafast transient absorption measurements revealed stimulated emission, which was absent for 4 before the hydrogenation, pointing toward the possible application of such hydrogenated nanographene molecules as optical gain materials, for example to develop an organic laser. Considering the directness and efficiency of π-truncation, this strategy could serve as a general approach to other unique aromatic structures not available by π-expansion, providing new candidates for (opto-)electronic devices and supramolecular chemistry.
Supporting Information
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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.9b00384.
Materials and methods, synthetic procedure, NMR, Raman, FT-IR spectroscopy and photoluminescence spectroscopy, transient absorption information (PDF)
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Author Information
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- Akimitsu Narita - Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany; Organic and Carbon Nanomaterials Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan;
http://orcid.org/0000-0002-3625-522X;
- Klaus Müllen - Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany; Institute of Physical Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany;http://orcid.org/0000-0001-6630-8786;
- Xiao-Ye Wang - Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany;http://orcid.org/0000-0003-3540-0277
- Giuseppe M. Paternò - Istituto Italiano di Tecnologia, Center for Nano Science and Technology, 20133 Milano, Italy;http://orcid.org/0000-0003-2349-566X
Acknowledgments
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This work was financially supported by Max Planck Society and the European Union’s Horizon 2020 research and innovation programme under Marie-Curie ITN project “iSwitch” (GA No.642196) and under Graphene Flagship (785219 GrapheneCore 2). X. Yao is grateful for the scholarship from China Council Scholarship (CSC).
References
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Stimulated by the challenge to address this long-standing problem, we and other org. chemists have envisioned a new prodn. strategy involving the controlled elongation of small hydrocarbon templates, such as hemispherical nanotube end-caps, prepd. by bottom-up chem. synthesis; the diam. and rim structure encoded in the template would dictate the diam. and chirality of the resulting CNT. Toward that objective, a short [5,5] CNT I has now been synthesized by stepwise chem. methods. This C50H10 geodesic polyarene has been isolated, purified, crystd., and fully characterized by NMR spectroscopy, UV-vis absorption spectroscopy, high resoln. mass spectrometry, and X-ray crystallog.(c) Scott, L. T.; Boorum, M. M.; McMahon, B. J.; Hagen, S.; Mack, J.; Blank, J.; Wegner, H.; de Meijere, A. A Rational Chemical Synthesis of C60. Science 2002, 295, 1500, DOI: 10.1126/science.1068427[Crossref], [PubMed], [CAS], Google Scholar6chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XhsFyqsL0%253D&md5=2b6ed9d2e7619219deece1198ee31136A rational chemical synthesis of C60Scott, Lawrence T.; Boorum, Margaret M.; McMahon, Brandon J.; Hagen, Stefan; Mack, James; Blank, Jarred; Wegner, Hermann; de Meijere, ArminScience (Washington, DC, United States) (2002), 295 (5559), 1500-1503CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Isolable quantities of C60, the smallest stable fullerene, have been synthesized in 12 steps from com. available starting materials by rational chem. methods. The polycyclic arom. precursor I bearing chlorine substituents at key positions forms C60 when subjected to flash vacuum pyrolysis at 1100°C. No other fullerenes are formed as byproducts. The methods here developed for the target-specific synthesis of fullerenes, applied to a synthesis of C60, should make possible the directed lab. prepn. of other fullerenes as well, including those not accessible by graphite vaporization. - 7(a) Clar, E.; Zander, M. 927. Syntheses of coronene and 1:2–7:8-dibenzocoronene. J. Chem. Soc. 1957, 4616– 4619, DOI: 10.1039/jr9570004616 .(b) Fort, E. H.; Donovan, P. M.; Scott, L. T. Diels–Alder Reactivity of Polycyclic Aromatic Hydrocarbon Bay Regions: Implications for Metal-Free Growth of Single-Chirality Carbon Nanotubes. J. Am. Chem. Soc. 2009, 131, 16006– 16007, DOI: 10.1021/ja907802g[ACS Full Text.], [CAS], Google Scholar7bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXht1OktbnE&md5=1a1640c374017ed953c3ffb60d256954Diels-Alder Reactivity of Polycyclic Aromatic Hydrocarbon Bay Regions: Implications for Metal-Free Growth of Single-Chirality Carbon NanotubesFort, Eric H.; Donovan, Patrick M.; Scott, Lawrence T.Journal of the American Chemical Society (2009), 131 (44), 16006-16007CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A sol. bisanthene deriv., 4,11-dimesitylbisanthene, has been synthesized in three steps from bianthrone. In hot toluene, this bisanthene undergoes a clean Diels-Alder reaction with di-Et acetylenedicarboxylate to give a rearomatized 1:1 cycloadduct and, more slowly, a rearomatized 2:1 cycloadduct. In a competition expt. with the shorter "periacene" perylene, only the bisanthene reacts, and the perylene remains unchanged. The exptl. results stand in complete accord with d. functional calcns. (B3LYP/6-31G*), which predict that the activation energies for Diels-Alder cycloaddns. in the bay regions of periacenes should diminish monotonically as the length of the mol. increases. This structure-activity relationship offers hope that single-chirality carbon nanotubes can be grown from suitable hydrocarbon templates, without metal catalysis, by a Diels-Alder cycloaddn./rearomatization strategy, using acetylene or a "masked acetylene" as the dienophile.(c) Fort, E. H.; Scott, L. T. Gas-phase Diels–Alder cycloaddition of benzyne to an aromatic hydrocarbon bay region: Groundwork for the selective solvent-free growth of armchair carbon nanotubes. Tetrahedron Lett. 2011, 52, 2051– 2053, DOI: 10.1016/j.tetlet.2010.10.033[Crossref], [CAS], Google Scholar.7chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXkt1yks70%253D&md5=2c8bf3fde641b97d3bc543f253072926Gas-phase Diels-Alder cycloaddition of benzyne to an aromatic hydrocarbon bay region: Groundwork for the selective solvent-free growth of armchair carbon nanotubesFort, Eric H.; Scott, Lawrence T.Tetrahedron Letters (2011), 52 (17), 2051-2053CODEN: TELEAY; ISSN:0040-4039. (Elsevier Ltd.)Benzyne, generated in the gas phase by pyrolysis of phthalic anhydride, has been shown to undergo Diels-Alder cycloaddn. to the bay region of perylene, a typical polycyclic arom. hydrocarbon, under solvent-free conditions in a high temp. flow system. The initial cycloadduct spontaneously loses two hydrogen atoms, thereby rearomatizing to give naphtho[1,2,3,4-ghi]perylene (I). Analogous Diels-Alder cycloaddn. of benzyne to bay regions on the rims of suitable cylindrical hydrocarbon templates, when followed by rearomatization and thermal cyclodehydrogenation to join adjacent benzo groups, are proposed as key steps for a directed chem. synthesis of uniform diam. armchair carbon nanotubes.(d) Konishi, A.; Hirao, Y.; Matsumoto, K.; Kurata, H.; Kubo, T. Facile Synthesis and Lateral π-Expansion of Bisanthenes. Chem. Lett. 2013, 42, 592– 594, DOI: 10.1246/cl.130153[Crossref], [CAS], Google Scholar.7dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtVSmsrzN&md5=70e458d606426bad7ebcff1ccfd80524Facile synthesis and lateral π-expansion of bisanthenesKonishi, Akihito; Hirao, Yasukazu; Matsumoto, Kouzou; Kurata, Hiroyuki; Kubo, TakashiChemistry Letters (2013), 42 (6), 592-594CODEN: CMLTAG; ISSN:0366-7022. (Chemical Society of Japan)The improved Scholl reaction allows for the direct cyclization of anthracene oligomers to give bisanthene, teranthene, and quateranthene. Furthermore, a variety of π-expanded bisanthenes are obtained by the Diels-Alder cycloaddn. of bisanthene with several arynes. These reactions would allow us to synthesize various size- and shape-controlled polyperiacenes.(e) Li, J.; Jiao, C.; Huang, K.-W.; Wu, J. Lateral Extension of π Conjugation along the Bay Regions of Bisanthene through a Diels–Alder Cycloaddition Reaction. Chem. - Eur. J. 2011, 17, 14672– 14680, DOI: 10.1002/chem.201102120[Crossref], [PubMed], [CAS], Google Scholar.7ehttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsVKgtb3F&md5=5199ab8c61f86a65f3adc4fb9f313ae0Lateral Extension of π Conjugation along the Bay Regions of Bisanthene through a Diels-Alder Cycloaddition ReactionLi, Jinling; Jiao, Chongjun; Huang, Kuo-Wei; Wu, JishanChemistry - A European Journal (2011), 17 (51), 14672-14680, S14672/1-S14672/37CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)Diels-Alder cycloaddn. reactions at the bay regions of 7,14-(3,5-di-tert-butylphenyl)bisanthene (I) with dienophiles such as 1,4-naphthoquinone have been investigated. The products were submitted to nucleophilic addn. followed by reductive aromatization reactions to afford the laterally extended bisanthene derivs. . Attempted synthesis of a larger expanded bisanthene revealed an unexpected hydrogenation reaction at the last reductive aromatization step. Unusual Michael addn. was obsd. on quinone deriv. which was obtained by Diels-Alder reaction between I and 1,4-anthraquinone. I and fused ring mono- and bis(1,4-(3,5-di-tert-butylphenyl)naphth-2,3-diyl) derivs. (II and III) exhibited near-IR (NIR) absorption and emission with high-to-moderate fluorescent quantum yields. Their structures and absorption spectra were studied by d. function theory and non-planar twisted structures were calcd. for II and III. All compds. showed amphoteric redox behavior with multiple oxidn./redn. waves. Oxidative titrn. with SbCl5 gave stable radical cations, and the process was followed by UV/Vis/NIR spectroscopic measurements. Their photostability was measured and correlated to their different geometries and electronic structures.(f) Schuler, B.; Collazos, S.; Gross, L.; Meyer, G.; Pérez, D.; Guitián, E.; Peña, D. From Perylene to a 22-Ring Aromatic Hydrocarbon in One-Pot. Angew. Chem., Int. Ed. 2014, 53, 9004– 9006, DOI: 10.1002/anie.201403707[Crossref], [CAS], Google Scholar7fhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVOisLvO&md5=43efc5ed8a6a6440dd896eab2e411fe1From perylene to a 22-ring aromatic hydrocarbon in one-potSchuler, Bruno; Collazos, Sara; Gross, Leo; Meyer, Gerhard; Perez, Dolores; Guitian, Enrique; Pena, DiegoAngewandte Chemie, International Edition (2014), 53 (34), 9004-9006CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The successful synthesis of the 3-fold sym. C78H36 mol. I with 22 fused benzene rings is reported. This clover-shaped nanographene was characterized on an ultrathin insulating film with at. resoln. by scanning probe microscopy.
- 8(a) Zhang, Q.; Kawasumi, K.; Segawa, Y.; Itami, K.; Scott, L. T. Palladium-Catalyzed C–H Activation Taken to the Limit. Flattening an Aromatic Bowl by Total Arylation. J. Am. Chem. Soc. 2012, 134, 15664– 15667, DOI: 10.1021/ja306992k[ACS Full Text.], [CAS], Google Scholar8ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlGkurvN&md5=584b5492cfbf258e4a187f98f83a5348Palladium-Catalyzed C-H Activation Taken to the Limit. Flattening an Aromatic Bowl by Total ArylationZhang, Qianyan; Kawasumi, Katsuaki; Segawa, Yasutomo; Itami, Kenichiro; Scott, Lawrence T.Journal of the American Chemical Society (2012), 134 (38), 15664-15667CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)All 10 C-H positions on the rim of corannulene can be arylated by repetitive palladium-catalyzed C-H activation. To relieve congestion among the 10 tightly packed aryl substituents in the product, the central corannulene adopts a nearly planar geometry.(b) Kawasumi, K.; Zhang, Q.; Segawa, Y.; Scott, L. T.; Itami, K. A grossly warped nanographene and the consequences of multiple odd-membered-ring defects. Nat. Chem. 2013, 5, 739, DOI: 10.1038/nchem.1704[Crossref], [PubMed], [CAS], Google Scholar8bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFSgtrnJ&md5=2d687d61c97466e84631bd321c6bab94A grossly warped nanographene and the consequences of multiple odd-membered-ring defectsKawasumi, Katsuaki; Zhang, Qianyan; Segawa, Yasutomo; Scott, Lawrence T.; Itami, KenichiroNature Chemistry (2013), 5 (9), 739-744CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Graphite, the most stable form of elemental carbon, consists of pure carbon sheets stacked upon one another like reams of paper. Individual sheets, known as graphene, prefer planar geometries as a consequence of the hexagonal honeycomb-like arrangements of trigonal carbon atoms that comprise their two-dimensional networks. Defects as nonhexagonal rings in such networks cause distortions away from planarity. Herein the authors report an extreme example of this phenomenon. A 26-ring C80H30 nanographene that incorporates five seven-membered rings and one five-membered ring embedded in a hexagonal lattice was synthesized by stepwise chem. methods, isolated, purified and fully characterized spectroscopically. Its grossly warped structure was revealed by single-crystal x-ray crystallog. An independent synthetic route to a freely sol. deriv. of this new type of nanocarbon' is also reported. Exptl. data reveal how the properties of such a large graphene subunit are affected by multiple odd-membered-ring defects.
- 9Watson, M. D.; Debije, M. G.; Warman, J. M.; Müllen, K. Peralkylated coronenes via regiospecific hydrogenation of hexa-peri-hexabenzocoronenes. J. Am. Chem. Soc. 2004, 126, 766– 771, DOI: 10.1021/ja037522+[ACS Full Text], [CAS], Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXjt1Cj&md5=10ccc9ea0c0939a9322e4621b6520865Peralkylated Coronenes via Regiospecific Hydrogenation of Hexa-peri-hexabenzocoronenesWatson, Mark D.; Debije, Michael G.; Warman, John M.; Muellen, KlausJournal of the American Chemical Society (2004), 126 (3), 766-771CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A remarkable, regiospecific hydrogenation zips around the ∼4 nm perimeter of hexa-peri-hexabenzocoronenes (HBC) adding 18 H atoms, leading to the first peralkylated coronenes, in quant. yields in some cases. Increasing steric bulk of side chains was found to hinder the reaction, while unsubstituted HBC could be converted to a modest extent despite its vanishing soly. The structures of the novel coronenes are unequivocally confirmed by MALDI-TOF, 1H, 13C, and heteronuclear correlation NMR, and UV-visible absorption spectroscopy. The puckered-ring periphery of these discotics does not prohibit self-assembly to columnar structures in a fashion similar to that of the planar precursors, as detd. from wide-angle x-ray diffraction, but decreases the isotropization temp. by ∼300° relative to the latter. Branching in the alkyl chains frustrates nucleation from the melt, resulting in clear polymorphism depending on the thermal treatment. Nonetheless, preliminary measurements indicate high charge-carrier mobilities and lifetimes within the bulk material, on the same order as those previously found for HBCs.
- 10Tashiro, S.; Yamada, M.; Shionoya, M. Iridium-Catalyzed Reductive Carbon–Carbon Bond Cleavage Reaction on a Curved Pyridylcorannulene Skeleton. Angew. Chem., Int. Ed. 2015, 54, 5351– 5354, DOI: 10.1002/anie.201500819[Crossref], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXkvF2murg%253D&md5=92810c62f7d71b4ab685d2337dc892caIridium-Catalyzed Reductive Carbon-Carbon Bond Cleavage Reaction on a Curved Pyridylcorannulene SkeletonTashiro, Shohei; Yamada, Mihoko; Shionoya, MitsuhikoAngewandte Chemie, International Edition (2015), 54 (18), 5351-5354CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The cleavage of C-C bonds in π-conjugated systems is an important method for controlling their shape and coplanarity. An efficient way for the cleavage of an arom. C-C bond in a typical buckybowl corannulene skeleton is reported. The reaction of 2-pyridylcorannulene with a catalytic amt. of IrCl3·nH2O in ethylene glycol at 250 °C resulted in a structural transformation from the curved corannulene skeleton to a strain-free flat benzo[ghi]fluoranthene skeleton through a site-selective C-C cleavage reaction. This cleavage reaction was found to be driven by both the coordination of the 2-pyridyl substituent to iridium and the relief of strain in the curved corannulene skeleton. This finding should facilitate the design of carbon nanomaterials based on C-C bond cleavage reactions.
- 11Matsuo, Y.; Tahara, K.; Sawamura, M.; Nakamura, E. Creation of hoop-and bowl-shaped benzenoid systems by selective detraction of [60] fullerene conjugation.[10] cyclophenacene and fused corannulene derivatives. J. Am. Chem. Soc. 2004, 126, 8725– 8734, DOI: 10.1021/ja048683w
- 12Clar, E.; Mackay, C. C. Circobiphenyl and the attempted synthesis of 1:14, 3:4, 7:8, 10:11-tetrabenzoperopyrene. Tetrahedron 1972, 28, 6041– 6047, DOI: 10.1016/0040-4020(72)88138-9[Crossref], [CAS], Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3sXhsF2gs7o%253D&md5=08bd0a851e8161a9f44293f6cef80eb7Circobiphenyl and the attempted synthesis of 1,14:3,4:7,8:10,11-tetrabenzoperopyreneClar, E.; Mackay, C. C.Tetrahedron (1972), 28 (24), 6041-7CODEN: TETRAB; ISSN:0040-4020.Reducing condensation of naphthanthrone (I) gave circobiphenyl (II), 3 isomeric dinaphthoperopyrenes, naphthanthrene, and 1,10-trimethylenepyrene. NMR data showed superaromaticity in II. Tetrabenzoperopyrene was not formed; it could not be prepd. from 2,5-dimethylterephthalic acid.
- 13Xiao, S.; Kang, S. J.; Wu, Y.; Ahn, S.; Kim, J. B.; Loo, Y.-L.; Siegrist, T.; Steigerwald, M. L.; Li, H.; Nuckolls, C. Supersized contorted aromatics. Chem. Sci. 2013, 4, 2018– 2023, DOI: 10.1039/c3sc50374g[Crossref], [CAS], Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXltVOltrc%253D&md5=fbd5b5c607eced31c6d5ce543f489d18Supersized contorted aromaticsXiao, Shengxiong; Kang, Seok Ju; Wu, Ying; Ahn, Seokhoon; Kim, Jong Bok; Loo, Yueh-Lin; Siegrist, Theo; Steigerwald, Michael L.; Li, Hexing; Nuckolls, ColinChemical Science (2013), 4 (5), 2018-2023CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)We describe here the synthesis and electronic device properties of a new type of polycyclic arom. mol., the contorted octabenzocircumbiphenyl (c-OBCB). Contorted polycyclic arom. hydrocarbons (PAHs) are promising small active mols. for org. devices. We present two different methods to synthesize c-OBCB derivs. that allow the smooth incorporation of functional groups. The material has a highly contorted exterior with six 4-helicenes and two 5-helicenes around the exterior of the expanded core of the arom. With appropriate sidechains, the material is sol. in common org. solvents and forms thin films. In thin films, the tetradodecyloxy-substituted c-OBCB self-assembles to form the active layer in org. field effect transistors. It is a hole transporting org. semiconductor. In the transistors, the c-OBCB forms good contact with source and drain contacts made from graphene. The c-OBCB self-assembles into a heterojunction from soln. with phenyl-C70-butyric acid Me ester (PC70BM). We obsd. power conversion efficiencies of ∼2.9 % under 100 mW cm-2 illumination at a 1 : 4 wt. ratio of the c-OBCB relative to PC70BM. The c-OBCB is shape complementary to the ball shaped PC70BM.
- 14Iyer, V. S.; Yoshimura, K.; Enkelmann, V.; Epsch, R.; Rabe, J. P.; Müllen, K. A Soluble C60 Graphite Segment. Angew. Chem., Int. Ed. 1998, 37, 2696– 2699, DOI: 10.1002/(SICI)1521-3773(19981016)37:19<2696::AID-ANIE2696>3.0.CO;2-E[Crossref], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXnt1Kruro%253D&md5=cd30920bc078b008faaa8c70bcd29288A soluble C60 graphite segmentIyer, Vivekanantan S.; Yoshimura, Kimihiro; Enkelmann, Volker; Epsch, Rebekka; Rabe, Jurgen P.; Mullen, KlausAngewandte Chemie, International Edition (1998), 37 (19), 2696-2699CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH)C60H22 PAH I (R = R1 = H) and its alkylated derivs. I (R = H, R1 = n-C12H25) and I (R = R1 = n-C12H25) were prepd. As a result of the soly. of the alkylated derivs., formation of monolayers is possible.
- 15Hudgins, D. M.; Sandford, S. A. Infrared Spectroscopy of Matrix Isolated Polycyclic Aromatic Hydrocarbons. 2. PAHs Containing Five or More Rings. J. Phys. Chem. A 1998, 102, 344– 352, DOI: 10.1021/jp983482y
- 16Wei, J.; Jia, X.; Yu, J.; Shi, X.; Zhang, C.; Chen, Z. Synthesis of 1,4,5,8,9,12-hexabromododecahydrotriphenylene and its application in constructing polycyclic thioaromatics. Chem. Commun. 2009, 31, 4714– 4716, DOI: 10.1039/b904477a
- 17(a) Wu, J.; Tomović, Ž.; Enkelmann, V.; Müllen, K. From Branched Hydrocarbon Propellers to C3-Symmetric Graphite Disks. J. Org. Chem. 2004, 69, 5179– 5186, DOI: 10.1021/jo049452a .(b) Casiraghi, C.; Ferrari, A. C.; Robertson, J. Raman spectroscopy of hydrogenated amorphous carbons. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72, 085401, DOI: 10.1103/PhysRevB.72.085401[Crossref], [CAS], Google Scholar17bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXhtVWqtLvM&md5=3787cc5d447333915c1db3dc6984044fRaman spectroscopy of hydrogenated amorphous carbonsCasiraghi, C.; Ferrari, A. C.; Robertson, J.Physical Review B: Condensed Matter and Materials Physics (2005), 72 (8), 085401/1-085401/14CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)A comprehensive multiwavelength Raman study is presented of a variety of hydrogenated amorphous carbons (a-C:H), ranging from polymeric a-C:H to diamond-like a-C:H and ta-C:H, which allows derivation of values for their bonding, d., band gap, H content, and mech. properties. The Raman spectra of a-C:Hs show 2 different trends. In 1 case, the G peak width increases with G peak dispersion. In the 2nd case, the opposite trend is found. In the 1st case, the Raman parameters vary with optical, structural, and mech. properties in the same way as in H-free C films. In the 2nd case, typical of polymeric a-C:H, the G peak width correlates with the d., while the G peak dispersion varies with the optical gap and H content. This allows a unified picture of bonding and disorder of all C films. UV Raman is particularly useful for a-C:Hs, as it gives clear measurements in the D and G peaks spectral region even for highly hydrogenated samples, for which the visible Raman spectra are overshadowed by luminescence. The slope of the luminescence background in visible Raman spectra can be used to est. the H content. UV Raman measurements allow the detection of C-H stretching vibrations.
- 18Kastler, M.; Pisula, W.; Wasserfallen, D.; Pakula, T.; Müllen, K. Influence of Alkyl Substituents on the Solution- and Surface-Organization of Hexa-peri-hexabenzocoronenes. J. Am. Chem. Soc. 2005, 127, 4286– 4296, DOI: 10.1021/ja0430696[ACS Full Text], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXitVWrs7w%253D&md5=9422fc0e50247b34ff89c405b161a766Influence of Alkyl Substituents on the Solution- and Surface-Organization of Hexa-peri-hexabenzocoronenesKastler, Marcel; Pisula, Wojciech; Wasserfallen, Daniel; Pakula, Tadeusz; Muellen, KlausJournal of the American Chemical Society (2005), 127 (12), 4286-4296CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Three hexa-peri-hexabenzocoronenes (HBCs) with branched, bulky alkyl substituents of different lengths in the periphery of the arom. core were synthesized to tune the self-assocn. properties in soln. 1H NMR and photophys. measurements were used to probe the soln. organization in comparison to the known hexa-dodecyl-substituted HBC in different solvent systems. Thermodn. parameters for the self-assocn. in soln., obtained by curve fitting of the concn.- and temp.-dependent NMR data using van't Hoff anal., indicated that the self-assocn. is an enthalpically driven process that is entropically disfavored. Photoluminescence and NMR results were both employed to det. the crit. concn. where no self-assocn. for different compds. occurred. The interactions between the mols. could be controlled by varying the nonsolvent content in the solvent mixts., supporting the model of solvophobic effects. The spatial demand of the solubilizing side chains modulated the self-assocn. in soln. This behavior was translated into the soln. casting process, where the kinetic in addn. to the thermodn. parameters played an essential role for structure formation. The study illuminates the relation between the soln. assocn. of HBCs and the morphol., when processed on a surface. These results are essential for the application of these materials in devices.
- 19Wasserfallen, D.; Kastler, M.; Pisula, W.; Hofer, W. A.; Fogel, Y.; Wang, Z.; Müllen, K. Suppressing Aggregation in a Large Polycyclic Aromatic Hydrocarbon. J. Am. Chem. Soc. 2006, 128, 1334– 1339, DOI: 10.1021/ja056782j[ACS Full Text], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XitVykug%253D%253D&md5=290b3a31b4b8ac6c8d5c851d6bbd9ae9Suppressing Aggregation in a Large Polycyclic Aromatic HydrocarbonWasserfallen, Daniel; Kastler, Marcel; Pisula, Wojciech; Hofer, Werner A.; Fogel, Yulia; Wang, Zhaohui; Muellen, KlausJournal of the American Chemical Society (2006), 128 (4), 1334-1339CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)With the approach presented herein, a large arom. π-system is synthesized, which shows extraordinarily high soly. and an effective suppression of aggregation. This was due to a distortion of the arom. core by bulky tert-Bu groups and the solubilizing effects of alkyl chains in the corona of the arom. core. Therefore not only the processing and cleaning of the materials with std. lab. techniques became possible, but moreover the first structure-rich UV/vis and a resolved 1H NMR spectra for an arom. system two times larger than hexa-peri-hexabenzocoronene were recorded. The bulk properties in an extruded fiber as well as on the surface showed a columnar self-assembly including a phase in which a homeotropic alignment on a substrate was obsd., which turns the material into an interesting candidate for future applications in electronic devices.
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- 22(a) Paternò, G. M.; Chen, Q.; Wang, X.-Y.; Liu, J.; Motti, S. G.; Petrozza, A.; Feng, X.; Lanzani, G.; Müllen, K.; Narita, A.; Scotognella, F. Synthesis of Dibenzo[hi,st]ovalene and Its Amplified Spontaneous Emission in a Polystyrene Matrix. Angew. Chem., Int. Ed. 2017, 56, 6753– 6757, DOI: 10.1002/ange.201700730 .(b) Paternò, G. M.; Nicoli, L.; Chen, Q.; Müllen, K.; Narita, A.; Lanzani, G.; Scotognella, F. Modulation of the Nonlinear Optical Properties of Dibenzo[hi,st]ovalene by Peripheral Substituents. J. Phys. Chem. C 2018, 122, 25007– 25013, DOI: 10.1021/acs.jpcc.8b06536[ACS Full Text], [CAS], Google Scholar22bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvV2js7jE&md5=ad5cb86ee8b3bbe833f491e3372dbeceModulation of the Nonlinear Optical Properties of Dibenzo[hi,st]ovalene by Peripheral SubstituentsPaterno, Giuseppe M.; Nicoli, Luca; Chen, Qiang; Mullen, Klaus; Narita, Akimitsu; Lanzani, Guglielmo; Scotognella, FrancescoJournal of Physical Chemistry C (2018), 122 (43), 25007-25013CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Dibenzo[hi,st]ovalene (DBOV) is a nanographene mol. with quasi-zero dimensional electronic confinement that displays relatively high oscillator strength, remarkable photostability, and optical gain property. For these reasons, DBOV has been proposed as a gain medium and active material for achieving strong exciton-photon coupling in microcavities. Here, we study the stimulated emission properties of three DBOV derivs. with different substitution patterns. We found that these mols. likely undergo ultrafast intermol. charge-transfer processes occurring within their π-aggregates, which ultimately leads to quenching of stimulated emission and increase of the amplified spontaneous emission threshold. These effects can be minimized by installing bulky substituents on the peripheries that prevent π-π stacking. Thus, by engineering the side groups, we can selectively favor either the luminescence/gain properties or the charge-transport features.
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- Marcel Dillenburger, Zijie Qiu, Cheng-Wei Ju, Beate Müller, Svenja Morsbach, Dieter Schollmeyer, Akimitsu Narita, Klaus Müllen. From Hexaphenylbenzene to 1,2,3,4,5,6-Hexacyclohexylcyclohexane. Journal of the American Chemical Society 2020, 142 (30) , 12916-12920. https://doi.org/10.1021/jacs.0c04956
- Paolo Fantuzzi, Andrea Candini, Qiang Chen, Xuelin Yao, Tim Dumslaff, Neeraj Mishra, Camilla Coletti, Klaus Müllen, Akimitsu Narita, Marco Affronte. Color Sensitive Response of Graphene/Graphene Quantum Dot Phototransistors. The Journal of Physical Chemistry C 2019, 123 (43) , 26490-26497. https://doi.org/10.1021/acs.jpcc.9b05013
- Xiaoqing Yu, Shuai Fu, Mukunda Mandal, Xuelin Yao, Zhaoyang Liu, Wenhao Zheng, Paolo Samorì, Akimitsu Narita, Klaus Müllen, Denis Andrienko, Mischa Bonn, Hai I. Wang. Tuning interfacial charge transfer in atomically precise nanographene–graphene heterostructures by engineering van der Waals interactions. The Journal of Chemical Physics 2022, 156 (7) , 074702. https://doi.org/10.1063/5.0081074
- Giuseppe M. Paternò, Qiang Chen, Rafael Muñoz-Mármol, Michele Guizzardi, Víctor Bonal, Ryota Kabe, Alexander J. Barker, Pedro G. Boj, Shreyam Chatterjee, Yutaka Ie, José M. Villalvilla, José A. Quintana, Francesco Scotognella, Klaus Müllen, María A. Díaz-García, Akimitsu Narita, Guglielmo Lanzani. Excited states engineering enables efficient near-infrared lasing in nanographenes. Materials Horizons 2022, 9 (1) , 393-402. https://doi.org/10.1039/D1MH00846C
- Giuseppe Maria Paternò, Goudappagouda, Qiang Chen, Guglielmo Lanzani, Francesco Scotognella, Akimitsu Narita. Large Polycyclic Aromatic Hydrocarbons as Graphene Quantum Dots: from Synthesis to Spectroscopy and Photonics. Advanced Optical Materials 2021, 9 (23) , 2100508. https://doi.org/10.1002/adom.202100508
- Zijie Qiu, Akimitsu Narita, Klaus Müllen. Spiers Memorial Lecture : Carbon nanostructures by macromolecular design – from branched polyphenylenes to nanographenes and graphene nanoribbons. Faraday Discussions 2021, 227 , 8-45. https://doi.org/10.1039/D0FD00023J
Abstract
Figure 1
Figure 1. “π-Expansion” toward circumbiphenyl 2 by E. Clar and the postsynthetic “π-truncation” to peralkylated circumbiphenyl 1.
Figure 2
Figure 2. High-resolution MALDI-TOF MS spectrum of 1 and 4 (inset: the corresponding experimental and simulated isotopic distributions of 1).
Figure 3
Figure 3. Representative FTIR spectra regions of 1 (blue line) and 4 (red line) measured on powder samples.
Figure 4
Figure 4. (a) Normalized UV–vis absorption and fluorescence spectra (excited at the absorption maxima) of 1 and 4 in THF solution (2 × 10–5 M) (inset: emission of 1 and 4 under 365 nm wavelength of UV lamp). (b) Frontier molecular orbitals and energy diagrams of 1, 2 and 4 at the B3LYP/6-311G(d) level. For simplicity of computation, dodecyl chains of 1 and 4 were removed.
Figure 5
Figure 5. (a) Femtosecond transient absorption spectra of 1 and 4 in THF solution at 1 fs pump–probe delay obtained by exciting at 470 nm and probing with a broadband probe light. (b) Transient dynamics for 1 and 4 at a probe wavelength of 500 nm. The solid blue and red lines represent the biexponential best-fit curves for 1 and 4, respectively.
References
ARTICLE SECTIONSThis article references 22 other publications.
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- 5(a) Xiao, S.; Myers, M.; Miao, Q.; Sanaur, S.; Pang, K.; Steigerwald, M. L.; Nuckolls, C. Molecular Wires from Contorted Aromatic Compounds. Angew. Chem., Int. Ed. 2005, 44, 7390– 7394, DOI: 10.1002/anie.200502142[Crossref], [CAS], Google Scholar.5ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXhtlSms77K&md5=8ef3fa50b05cd0af3b112d01ef2af52eMolecular wires from contorted aromatic compoundsXiao, Shengxiong; Myers, Matthew; Miao, Qian; Sanaur, Sebastien; Pang, Keliang; Steigerwald, Michael L.; Nuckolls, ColinAngewandte Chemie, International Edition (2005), 44 (45), 7390-7394CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A design strategy for mol.-based electronic materials using arom. compds. with a nonplanar core is presented. A new class of hexabenzocoronene is put forth that has its core severely distorted out of planarity into a corrugated structure. When substituted with four alkoxy side chains, this material self-assembles into infinitely long columns through stacking and acts as an active layer in field-effect transistors.(b) Chiu, C.-Y.; Kim, B.; Gorodetsky, A. A.; Sattler, W.; Wei, S.; Sattler, A.; Steigerwald, M.; Nuckolls, C. Shape-shifting in contorted dibenzotetrathienocoronenes. Chem. Sci. 2011, 2, 1480– 1486, DOI: 10.1039/C1SC00156F[Crossref], [CAS], Google Scholar.5bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXoslWlur4%253D&md5=c04bfa2266894524929d70b242c721a9Shape-shifting in contorted dibenzotetrathienocoronenesChiu, Chien-Yang; Kim, Bumjung; Gorodetsky, Alon A.; Sattler, Wesley; Wei, Sujun; Sattler, Aaron; Steigerwald, Michael; Nuckolls, ColinChemical Science (2011), 2 (8), 1480-1486CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)The authors detail a general method for the synthesis of dibenzotetrathienocoronenes and elucidate their solid state structures in crystals and co-crystals. The contorted dibenzotetrathienocoronene (c-DBTTC) is a tetrathiophene-fused version of the previously studied contorted hexabenzocoronenes (c-HBC). The synthesis detailed here is simple and provides easy access to this important class of materials. These materials display mol. flexibility and tunable supramol. self-assembly properties in the solid state by shifting mol. conformations between two different conformations. Depending on the conditions under which a c-DBTTC-contg. material crystallizes, the c-DBTTC adopts either the up-down or the butterfly conformation. When grown from the vapor phase, crystals of the unsubstituted c-DBTTC show the mol. only in the up-down conformation, and it packs into dense crystals contg. columnar arrays with close intracolumnar packing. The packing is controlled by the inherent mol. corrugation of the three-dimensional core and sulfur-sulfur interactions. When grown as co-crystals with electron acceptors from soln., the butyl-substituted c-DBTTC either adopts the butterfly conformation when the electron acceptor is small enough to be completely enveloped (TCNQ) or the up-down conformation when the electron acceptor is relatively large (C60). When grown from org. solvent crystals of the butyl-substituted c-DBTTC contain mols. of the solvent as the only guest, and the authors observe both conformations of the c-DBTTC. Controlling the supramol. structure is the key to developing these materials for electronic applications.(c) Daigle, M.; Picard-Lafond, A.; Soligo, E.; Morin, J.-F. Regioselective Synthesis of Nanographenes by Photochemical Cyclodehydrochlorination. Angew. Chem., Int. Ed. 2016, 55, 2042– 2047, DOI: 10.1002/anie.201509130[Crossref], [CAS], Google Scholar5chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitVygurvP&md5=73ba14b4381a808afbc799310ea344dcRegioselective Synthesis of Nanographenes by Photochemical CyclodehydrochlorinationDaigle, Maxime; Picard-Lafond, Audrey; Soligo, Eliane; Morin, Jean-FrancoisAngewandte Chemie, International Edition (2016), 55 (6), 2042-2047CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Novel nanographenes were prepd. by a photochem. cyclodehydrochlorination (CDHC, cyclization) reaction. Chlorinated precursors were irradiated in acetone in the presence of a base or in pure benzene and underwent multiple (up to four) regioselective cyclization reactions to provide rigid π-conjugated mols. Pure compds. were recovered in good yields by simple filtration at the end of the reaction. The CDHC reaction showed compatibility with both electron-poor and electron-rich substrates, thus allowing the synthesis of pyridine- and thiophene-fused nanographenes. It also enabled the synthesis of sterically hindered contorted π-conjugated mols. without causing full aromatization. A kinetic study showed that the CDHC reaction under the conditions used is a very fast process, and some reactions are completed within minutes. The CDHC reaction thus shows great potential as an alternative to other reactions involving harsher conditions for the prepn. of nanographenes. Starting materials included 2-chloro-1,1':2',1''-terphenyl, (chlorobiphenyl)pyridine, 2-(2,3-dichlorophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 1,4-dichloro-2,5-diiodobenzene. The title compds. thus formed included triphenylene, dibenzo[f,j]picene, phenanthro[9,10-b]triphenylene, dibenzo[ij,rst]phenanthro[9,10,1,2-defg]pentaphene, dibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene, dibenz[f,h]isoquinoline.
- 6(a) Scott, L. T.; Cheng, P.-C.; Hashemi, M. M.; Bratcher, M. S.; Meyer, D. T.; Warren, H. B. Corannulene. A Three-Step Synthesis1. J. Am. Chem. Soc. 1997, 119, 10963– 10968, DOI: 10.1021/ja972019g .(b) Scott, L. T.; Jackson, E. A.; Zhang, Q.; Steinberg, B. D.; Bancu, M.; Li, B. A Short, Rigid, Structurally Pure Carbon Nanotube by Stepwise Chemical Synthesis. J. Am. Chem. Soc. 2012, 134, 107– 110, DOI: 10.1021/ja209461g[ACS Full Text.], [CAS], Google Scholar6bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsFGmtL%252FL&md5=3607f961a10ed6da83ea1223b40b7baeA Short, Rigid, Structurally Pure Carbon Nanotube by Stepwise Chemical SynthesisScott, Lawrence T.; Jackson, Edward A.; Zhang, Qianyan; Steinberg, Brian D.; Bancu, Mihail; Li, BoJournal of the American Chemical Society (2012), 134 (1), 107-110CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The inaccessibility of uniform-diam., single-chirality carbon nanotubes (CNTs) in pure form continues to thwart efforts by scientists to use these ultrathin materials in innovative applications that could revolutionize nanoscale electronics. Stimulated by the challenge to address this long-standing problem, we and other org. chemists have envisioned a new prodn. strategy involving the controlled elongation of small hydrocarbon templates, such as hemispherical nanotube end-caps, prepd. by bottom-up chem. synthesis; the diam. and rim structure encoded in the template would dictate the diam. and chirality of the resulting CNT. Toward that objective, a short [5,5] CNT I has now been synthesized by stepwise chem. methods. This C50H10 geodesic polyarene has been isolated, purified, crystd., and fully characterized by NMR spectroscopy, UV-vis absorption spectroscopy, high resoln. mass spectrometry, and X-ray crystallog.(c) Scott, L. T.; Boorum, M. M.; McMahon, B. J.; Hagen, S.; Mack, J.; Blank, J.; Wegner, H.; de Meijere, A. A Rational Chemical Synthesis of C60. Science 2002, 295, 1500, DOI: 10.1126/science.1068427[Crossref], [PubMed], [CAS], Google Scholar6chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XhsFyqsL0%253D&md5=2b6ed9d2e7619219deece1198ee31136A rational chemical synthesis of C60Scott, Lawrence T.; Boorum, Margaret M.; McMahon, Brandon J.; Hagen, Stefan; Mack, James; Blank, Jarred; Wegner, Hermann; de Meijere, ArminScience (Washington, DC, United States) (2002), 295 (5559), 1500-1503CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Isolable quantities of C60, the smallest stable fullerene, have been synthesized in 12 steps from com. available starting materials by rational chem. methods. The polycyclic arom. precursor I bearing chlorine substituents at key positions forms C60 when subjected to flash vacuum pyrolysis at 1100°C. No other fullerenes are formed as byproducts. The methods here developed for the target-specific synthesis of fullerenes, applied to a synthesis of C60, should make possible the directed lab. prepn. of other fullerenes as well, including those not accessible by graphite vaporization.
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(American Chemical Society)A sol. bisanthene deriv., 4,11-dimesitylbisanthene, has been synthesized in three steps from bianthrone. In hot toluene, this bisanthene undergoes a clean Diels-Alder reaction with di-Et acetylenedicarboxylate to give a rearomatized 1:1 cycloadduct and, more slowly, a rearomatized 2:1 cycloadduct. In a competition expt. with the shorter "periacene" perylene, only the bisanthene reacts, and the perylene remains unchanged. The exptl. results stand in complete accord with d. functional calcns. (B3LYP/6-31G*), which predict that the activation energies for Diels-Alder cycloaddns. in the bay regions of periacenes should diminish monotonically as the length of the mol. increases. This structure-activity relationship offers hope that single-chirality carbon nanotubes can be grown from suitable hydrocarbon templates, without metal catalysis, by a Diels-Alder cycloaddn./rearomatization strategy, using acetylene or a "masked acetylene" as the dienophile.(c) Fort, E. H.; Scott, L. T. Gas-phase Diels–Alder cycloaddition of benzyne to an aromatic hydrocarbon bay region: Groundwork for the selective solvent-free growth of armchair carbon nanotubes. Tetrahedron Lett. 2011, 52, 2051– 2053, DOI: 10.1016/j.tetlet.2010.10.033[Crossref], [CAS], Google Scholar.7chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXkt1yks70%253D&md5=2c8bf3fde641b97d3bc543f253072926Gas-phase Diels-Alder cycloaddition of benzyne to an aromatic hydrocarbon bay region: Groundwork for the selective solvent-free growth of armchair carbon nanotubesFort, Eric H.; Scott, Lawrence T.Tetrahedron Letters (2011), 52 (17), 2051-2053CODEN: TELEAY; ISSN:0040-4039. (Elsevier Ltd.)Benzyne, generated in the gas phase by pyrolysis of phthalic anhydride, has been shown to undergo Diels-Alder cycloaddn. to the bay region of perylene, a typical polycyclic arom. hydrocarbon, under solvent-free conditions in a high temp. flow system. The initial cycloadduct spontaneously loses two hydrogen atoms, thereby rearomatizing to give naphtho[1,2,3,4-ghi]perylene (I). Analogous Diels-Alder cycloaddn. of benzyne to bay regions on the rims of suitable cylindrical hydrocarbon templates, when followed by rearomatization and thermal cyclodehydrogenation to join adjacent benzo groups, are proposed as key steps for a directed chem. synthesis of uniform diam. armchair carbon nanotubes.(d) Konishi, A.; Hirao, Y.; Matsumoto, K.; Kurata, H.; Kubo, T. Facile Synthesis and Lateral π-Expansion of Bisanthenes. Chem. Lett. 2013, 42, 592– 594, DOI: 10.1246/cl.130153[Crossref], [CAS], Google Scholar.7dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtVSmsrzN&md5=70e458d606426bad7ebcff1ccfd80524Facile synthesis and lateral π-expansion of bisanthenesKonishi, Akihito; Hirao, Yasukazu; Matsumoto, Kouzou; Kurata, Hiroyuki; Kubo, TakashiChemistry Letters (2013), 42 (6), 592-594CODEN: CMLTAG; ISSN:0366-7022. (Chemical Society of Japan)The improved Scholl reaction allows for the direct cyclization of anthracene oligomers to give bisanthene, teranthene, and quateranthene. Furthermore, a variety of π-expanded bisanthenes are obtained by the Diels-Alder cycloaddn. of bisanthene with several arynes. These reactions would allow us to synthesize various size- and shape-controlled polyperiacenes.(e) Li, J.; Jiao, C.; Huang, K.-W.; Wu, J. Lateral Extension of π Conjugation along the Bay Regions of Bisanthene through a Diels–Alder Cycloaddition Reaction. Chem. - Eur. J. 2011, 17, 14672– 14680, DOI: 10.1002/chem.201102120[Crossref], [PubMed], [CAS], Google Scholar.7ehttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsVKgtb3F&md5=5199ab8c61f86a65f3adc4fb9f313ae0Lateral Extension of π Conjugation along the Bay Regions of Bisanthene through a Diels-Alder Cycloaddition ReactionLi, Jinling; Jiao, Chongjun; Huang, Kuo-Wei; Wu, JishanChemistry - A European Journal (2011), 17 (51), 14672-14680, S14672/1-S14672/37CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)Diels-Alder cycloaddn. reactions at the bay regions of 7,14-(3,5-di-tert-butylphenyl)bisanthene (I) with dienophiles such as 1,4-naphthoquinone have been investigated. The products were submitted to nucleophilic addn. followed by reductive aromatization reactions to afford the laterally extended bisanthene derivs. . Attempted synthesis of a larger expanded bisanthene revealed an unexpected hydrogenation reaction at the last reductive aromatization step. Unusual Michael addn. was obsd. on quinone deriv. which was obtained by Diels-Alder reaction between I and 1,4-anthraquinone. I and fused ring mono- and bis(1,4-(3,5-di-tert-butylphenyl)naphth-2,3-diyl) derivs. (II and III) exhibited near-IR (NIR) absorption and emission with high-to-moderate fluorescent quantum yields. Their structures and absorption spectra were studied by d. function theory and non-planar twisted structures were calcd. for II and III. All compds. showed amphoteric redox behavior with multiple oxidn./redn. waves. Oxidative titrn. with SbCl5 gave stable radical cations, and the process was followed by UV/Vis/NIR spectroscopic measurements. Their photostability was measured and correlated to their different geometries and electronic structures.(f) Schuler, B.; Collazos, S.; Gross, L.; Meyer, G.; Pérez, D.; Guitián, E.; Peña, D. From Perylene to a 22-Ring Aromatic Hydrocarbon in One-Pot. Angew. Chem., Int. Ed. 2014, 53, 9004– 9006, DOI: 10.1002/anie.201403707[Crossref], [CAS], Google Scholar7fhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVOisLvO&md5=43efc5ed8a6a6440dd896eab2e411fe1From perylene to a 22-ring aromatic hydrocarbon in one-potSchuler, Bruno; Collazos, Sara; Gross, Leo; Meyer, Gerhard; Perez, Dolores; Guitian, Enrique; Pena, DiegoAngewandte Chemie, International Edition (2014), 53 (34), 9004-9006CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The successful synthesis of the 3-fold sym. C78H36 mol. I with 22 fused benzene rings is reported. This clover-shaped nanographene was characterized on an ultrathin insulating film with at. resoln. by scanning probe microscopy.
- 8(a) Zhang, Q.; Kawasumi, K.; Segawa, Y.; Itami, K.; Scott, L. T. Palladium-Catalyzed C–H Activation Taken to the Limit. Flattening an Aromatic Bowl by Total Arylation. J. Am. Chem. Soc. 2012, 134, 15664– 15667, DOI: 10.1021/ja306992k[ACS Full Text.], [CAS], Google Scholar8ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlGkurvN&md5=584b5492cfbf258e4a187f98f83a5348Palladium-Catalyzed C-H Activation Taken to the Limit. Flattening an Aromatic Bowl by Total ArylationZhang, Qianyan; Kawasumi, Katsuaki; Segawa, Yasutomo; Itami, Kenichiro; Scott, Lawrence T.Journal of the American Chemical Society (2012), 134 (38), 15664-15667CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)All 10 C-H positions on the rim of corannulene can be arylated by repetitive palladium-catalyzed C-H activation. To relieve congestion among the 10 tightly packed aryl substituents in the product, the central corannulene adopts a nearly planar geometry.(b) Kawasumi, K.; Zhang, Q.; Segawa, Y.; Scott, L. T.; Itami, K. A grossly warped nanographene and the consequences of multiple odd-membered-ring defects. Nat. Chem. 2013, 5, 739, DOI: 10.1038/nchem.1704[Crossref], [PubMed], [CAS], Google Scholar8bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFSgtrnJ&md5=2d687d61c97466e84631bd321c6bab94A grossly warped nanographene and the consequences of multiple odd-membered-ring defectsKawasumi, Katsuaki; Zhang, Qianyan; Segawa, Yasutomo; Scott, Lawrence T.; Itami, KenichiroNature Chemistry (2013), 5 (9), 739-744CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Graphite, the most stable form of elemental carbon, consists of pure carbon sheets stacked upon one another like reams of paper. Individual sheets, known as graphene, prefer planar geometries as a consequence of the hexagonal honeycomb-like arrangements of trigonal carbon atoms that comprise their two-dimensional networks. Defects as nonhexagonal rings in such networks cause distortions away from planarity. Herein the authors report an extreme example of this phenomenon. A 26-ring C80H30 nanographene that incorporates five seven-membered rings and one five-membered ring embedded in a hexagonal lattice was synthesized by stepwise chem. methods, isolated, purified and fully characterized spectroscopically. Its grossly warped structure was revealed by single-crystal x-ray crystallog. An independent synthetic route to a freely sol. deriv. of this new type of nanocarbon' is also reported. Exptl. data reveal how the properties of such a large graphene subunit are affected by multiple odd-membered-ring defects.
- 9Watson, M. D.; Debije, M. G.; Warman, J. M.; Müllen, K. Peralkylated coronenes via regiospecific hydrogenation of hexa-peri-hexabenzocoronenes. J. Am. Chem. Soc. 2004, 126, 766– 771, DOI: 10.1021/ja037522+[ACS Full Text], [CAS], Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXjt1Cj&md5=10ccc9ea0c0939a9322e4621b6520865Peralkylated Coronenes via Regiospecific Hydrogenation of Hexa-peri-hexabenzocoronenesWatson, Mark D.; Debije, Michael G.; Warman, John M.; Muellen, KlausJournal of the American Chemical Society (2004), 126 (3), 766-771CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A remarkable, regiospecific hydrogenation zips around the ∼4 nm perimeter of hexa-peri-hexabenzocoronenes (HBC) adding 18 H atoms, leading to the first peralkylated coronenes, in quant. yields in some cases. Increasing steric bulk of side chains was found to hinder the reaction, while unsubstituted HBC could be converted to a modest extent despite its vanishing soly. The structures of the novel coronenes are unequivocally confirmed by MALDI-TOF, 1H, 13C, and heteronuclear correlation NMR, and UV-visible absorption spectroscopy. The puckered-ring periphery of these discotics does not prohibit self-assembly to columnar structures in a fashion similar to that of the planar precursors, as detd. from wide-angle x-ray diffraction, but decreases the isotropization temp. by ∼300° relative to the latter. Branching in the alkyl chains frustrates nucleation from the melt, resulting in clear polymorphism depending on the thermal treatment. Nonetheless, preliminary measurements indicate high charge-carrier mobilities and lifetimes within the bulk material, on the same order as those previously found for HBCs.
- 10Tashiro, S.; Yamada, M.; Shionoya, M. Iridium-Catalyzed Reductive Carbon–Carbon Bond Cleavage Reaction on a Curved Pyridylcorannulene Skeleton. Angew. Chem., Int. Ed. 2015, 54, 5351– 5354, DOI: 10.1002/anie.201500819[Crossref], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXkvF2murg%253D&md5=92810c62f7d71b4ab685d2337dc892caIridium-Catalyzed Reductive Carbon-Carbon Bond Cleavage Reaction on a Curved Pyridylcorannulene SkeletonTashiro, Shohei; Yamada, Mihoko; Shionoya, MitsuhikoAngewandte Chemie, International Edition (2015), 54 (18), 5351-5354CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The cleavage of C-C bonds in π-conjugated systems is an important method for controlling their shape and coplanarity. An efficient way for the cleavage of an arom. C-C bond in a typical buckybowl corannulene skeleton is reported. The reaction of 2-pyridylcorannulene with a catalytic amt. of IrCl3·nH2O in ethylene glycol at 250 °C resulted in a structural transformation from the curved corannulene skeleton to a strain-free flat benzo[ghi]fluoranthene skeleton through a site-selective C-C cleavage reaction. This cleavage reaction was found to be driven by both the coordination of the 2-pyridyl substituent to iridium and the relief of strain in the curved corannulene skeleton. This finding should facilitate the design of carbon nanomaterials based on C-C bond cleavage reactions.
- 11Matsuo, Y.; Tahara, K.; Sawamura, M.; Nakamura, E. Creation of hoop-and bowl-shaped benzenoid systems by selective detraction of [60] fullerene conjugation.[10] cyclophenacene and fused corannulene derivatives. J. Am. Chem. Soc. 2004, 126, 8725– 8734, DOI: 10.1021/ja048683w
- 12Clar, E.; Mackay, C. C. Circobiphenyl and the attempted synthesis of 1:14, 3:4, 7:8, 10:11-tetrabenzoperopyrene. Tetrahedron 1972, 28, 6041– 6047, DOI: 10.1016/0040-4020(72)88138-9[Crossref], [CAS], Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3sXhsF2gs7o%253D&md5=08bd0a851e8161a9f44293f6cef80eb7Circobiphenyl and the attempted synthesis of 1,14:3,4:7,8:10,11-tetrabenzoperopyreneClar, E.; Mackay, C. C.Tetrahedron (1972), 28 (24), 6041-7CODEN: TETRAB; ISSN:0040-4020.Reducing condensation of naphthanthrone (I) gave circobiphenyl (II), 3 isomeric dinaphthoperopyrenes, naphthanthrene, and 1,10-trimethylenepyrene. NMR data showed superaromaticity in II. Tetrabenzoperopyrene was not formed; it could not be prepd. from 2,5-dimethylterephthalic acid.
- 13Xiao, S.; Kang, S. J.; Wu, Y.; Ahn, S.; Kim, J. B.; Loo, Y.-L.; Siegrist, T.; Steigerwald, M. L.; Li, H.; Nuckolls, C. Supersized contorted aromatics. Chem. Sci. 2013, 4, 2018– 2023, DOI: 10.1039/c3sc50374g[Crossref], [CAS], Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXltVOltrc%253D&md5=fbd5b5c607eced31c6d5ce543f489d18Supersized contorted aromaticsXiao, Shengxiong; Kang, Seok Ju; Wu, Ying; Ahn, Seokhoon; Kim, Jong Bok; Loo, Yueh-Lin; Siegrist, Theo; Steigerwald, Michael L.; Li, Hexing; Nuckolls, ColinChemical Science (2013), 4 (5), 2018-2023CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)We describe here the synthesis and electronic device properties of a new type of polycyclic arom. mol., the contorted octabenzocircumbiphenyl (c-OBCB). Contorted polycyclic arom. hydrocarbons (PAHs) are promising small active mols. for org. devices. We present two different methods to synthesize c-OBCB derivs. that allow the smooth incorporation of functional groups. The material has a highly contorted exterior with six 4-helicenes and two 5-helicenes around the exterior of the expanded core of the arom. With appropriate sidechains, the material is sol. in common org. solvents and forms thin films. In thin films, the tetradodecyloxy-substituted c-OBCB self-assembles to form the active layer in org. field effect transistors. It is a hole transporting org. semiconductor. In the transistors, the c-OBCB forms good contact with source and drain contacts made from graphene. The c-OBCB self-assembles into a heterojunction from soln. with phenyl-C70-butyric acid Me ester (PC70BM). We obsd. power conversion efficiencies of ∼2.9 % under 100 mW cm-2 illumination at a 1 : 4 wt. ratio of the c-OBCB relative to PC70BM. The c-OBCB is shape complementary to the ball shaped PC70BM.
- 14Iyer, V. S.; Yoshimura, K.; Enkelmann, V.; Epsch, R.; Rabe, J. P.; Müllen, K. A Soluble C60 Graphite Segment. Angew. Chem., Int. Ed. 1998, 37, 2696– 2699, DOI: 10.1002/(SICI)1521-3773(19981016)37:19<2696::AID-ANIE2696>3.0.CO;2-E[Crossref], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXnt1Kruro%253D&md5=cd30920bc078b008faaa8c70bcd29288A soluble C60 graphite segmentIyer, Vivekanantan S.; Yoshimura, Kimihiro; Enkelmann, Volker; Epsch, Rebekka; Rabe, Jurgen P.; Mullen, KlausAngewandte Chemie, International Edition (1998), 37 (19), 2696-2699CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH)C60H22 PAH I (R = R1 = H) and its alkylated derivs. I (R = H, R1 = n-C12H25) and I (R = R1 = n-C12H25) were prepd. As a result of the soly. of the alkylated derivs., formation of monolayers is possible.
- 15Hudgins, D. M.; Sandford, S. A. Infrared Spectroscopy of Matrix Isolated Polycyclic Aromatic Hydrocarbons. 2. PAHs Containing Five or More Rings. J. Phys. Chem. A 1998, 102, 344– 352, DOI: 10.1021/jp983482y
- 16Wei, J.; Jia, X.; Yu, J.; Shi, X.; Zhang, C.; Chen, Z. Synthesis of 1,4,5,8,9,12-hexabromododecahydrotriphenylene and its application in constructing polycyclic thioaromatics. Chem. Commun. 2009, 31, 4714– 4716, DOI: 10.1039/b904477a
- 17(a) Wu, J.; Tomović, Ž.; Enkelmann, V.; Müllen, K. From Branched Hydrocarbon Propellers to C3-Symmetric Graphite Disks. J. Org. Chem. 2004, 69, 5179– 5186, DOI: 10.1021/jo049452a .(b) Casiraghi, C.; Ferrari, A. C.; Robertson, J. Raman spectroscopy of hydrogenated amorphous carbons. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72, 085401, DOI: 10.1103/PhysRevB.72.085401[Crossref], [CAS], Google Scholar17bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXhtVWqtLvM&md5=3787cc5d447333915c1db3dc6984044fRaman spectroscopy of hydrogenated amorphous carbonsCasiraghi, C.; Ferrari, A. C.; Robertson, J.Physical Review B: Condensed Matter and Materials Physics (2005), 72 (8), 085401/1-085401/14CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)A comprehensive multiwavelength Raman study is presented of a variety of hydrogenated amorphous carbons (a-C:H), ranging from polymeric a-C:H to diamond-like a-C:H and ta-C:H, which allows derivation of values for their bonding, d., band gap, H content, and mech. properties. The Raman spectra of a-C:Hs show 2 different trends. In 1 case, the G peak width increases with G peak dispersion. In the 2nd case, the opposite trend is found. In the 1st case, the Raman parameters vary with optical, structural, and mech. properties in the same way as in H-free C films. In the 2nd case, typical of polymeric a-C:H, the G peak width correlates with the d., while the G peak dispersion varies with the optical gap and H content. This allows a unified picture of bonding and disorder of all C films. UV Raman is particularly useful for a-C:Hs, as it gives clear measurements in the D and G peaks spectral region even for highly hydrogenated samples, for which the visible Raman spectra are overshadowed by luminescence. The slope of the luminescence background in visible Raman spectra can be used to est. the H content. UV Raman measurements allow the detection of C-H stretching vibrations.
- 18Kastler, M.; Pisula, W.; Wasserfallen, D.; Pakula, T.; Müllen, K. Influence of Alkyl Substituents on the Solution- and Surface-Organization of Hexa-peri-hexabenzocoronenes. J. Am. Chem. Soc. 2005, 127, 4286– 4296, DOI: 10.1021/ja0430696[ACS Full Text], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXitVWrs7w%253D&md5=9422fc0e50247b34ff89c405b161a766Influence of Alkyl Substituents on the Solution- and Surface-Organization of Hexa-peri-hexabenzocoronenesKastler, Marcel; Pisula, Wojciech; Wasserfallen, Daniel; Pakula, Tadeusz; Muellen, KlausJournal of the American Chemical Society (2005), 127 (12), 4286-4296CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Three hexa-peri-hexabenzocoronenes (HBCs) with branched, bulky alkyl substituents of different lengths in the periphery of the arom. core were synthesized to tune the self-assocn. properties in soln. 1H NMR and photophys. measurements were used to probe the soln. organization in comparison to the known hexa-dodecyl-substituted HBC in different solvent systems. Thermodn. parameters for the self-assocn. in soln., obtained by curve fitting of the concn.- and temp.-dependent NMR data using van't Hoff anal., indicated that the self-assocn. is an enthalpically driven process that is entropically disfavored. Photoluminescence and NMR results were both employed to det. the crit. concn. where no self-assocn. for different compds. occurred. The interactions between the mols. could be controlled by varying the nonsolvent content in the solvent mixts., supporting the model of solvophobic effects. The spatial demand of the solubilizing side chains modulated the self-assocn. in soln. This behavior was translated into the soln. casting process, where the kinetic in addn. to the thermodn. parameters played an essential role for structure formation. The study illuminates the relation between the soln. assocn. of HBCs and the morphol., when processed on a surface. These results are essential for the application of these materials in devices.
- 19Wasserfallen, D.; Kastler, M.; Pisula, W.; Hofer, W. A.; Fogel, Y.; Wang, Z.; Müllen, K. Suppressing Aggregation in a Large Polycyclic Aromatic Hydrocarbon. J. Am. Chem. Soc. 2006, 128, 1334– 1339, DOI: 10.1021/ja056782j[ACS Full Text], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XitVykug%253D%253D&md5=290b3a31b4b8ac6c8d5c851d6bbd9ae9Suppressing Aggregation in a Large Polycyclic Aromatic HydrocarbonWasserfallen, Daniel; Kastler, Marcel; Pisula, Wojciech; Hofer, Werner A.; Fogel, Yulia; Wang, Zhaohui; Muellen, KlausJournal of the American Chemical Society (2006), 128 (4), 1334-1339CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)With the approach presented herein, a large arom. π-system is synthesized, which shows extraordinarily high soly. and an effective suppression of aggregation. This was due to a distortion of the arom. core by bulky tert-Bu groups and the solubilizing effects of alkyl chains in the corona of the arom. core. Therefore not only the processing and cleaning of the materials with std. lab. techniques became possible, but moreover the first structure-rich UV/vis and a resolved 1H NMR spectra for an arom. system two times larger than hexa-peri-hexabenzocoronene were recorded. The bulk properties in an extruded fiber as well as on the surface showed a columnar self-assembly including a phase in which a homeotropic alignment on a substrate was obsd., which turns the material into an interesting candidate for future applications in electronic devices.
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- 21Cabanillas-Gonzalez, J.; Grancini, G.; Lanzani, G. Pump-Probe Spectroscopy in Organic Semiconductors: Monitoring Fundamental Processes of Relevance in Optoelectronics. Adv. Mater. 2011, 23, 5468– 5485, DOI: 10.1002/adma.201102015[Crossref], [PubMed], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlKgurbK&md5=485c9ae1395b490f6afcc9a8c1cb6d49Pump-Probe Spectroscopy in Organic Semiconductors: Monitoring Fundamental Processes of Relevance in OptoelectronicsCabanillas-Gonzalez, Juan; Grancini, Giulia; Lanzani, GuglielmoAdvanced Materials (Weinheim, Germany) (2011), 23 (46), 5468-5485CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. In this review the authors highlight the contribution of pump-probe spectroscopy to understand elementary processes taking place in org. based optoelectronic devices. The techniques described in this article span from conventional pump-probe spectroscopy to electromodulated pump-probe and the state-of-the-art confocal pump-probe microscopy. The article is structured according to 3 fundamental processes (optical gain, charge photogeneration and charge transport) and the contribution of these techniques on them. The combination of these tools opens up new perspectives for assessing the role of short-lived excited states on processes lying underneath org. device operation.
- 22(a) Paternò, G. M.; Chen, Q.; Wang, X.-Y.; Liu, J.; Motti, S. G.; Petrozza, A.; Feng, X.; Lanzani, G.; Müllen, K.; Narita, A.; Scotognella, F. Synthesis of Dibenzo[hi,st]ovalene and Its Amplified Spontaneous Emission in a Polystyrene Matrix. Angew. Chem., Int. Ed. 2017, 56, 6753– 6757, DOI: 10.1002/ange.201700730 .(b) Paternò, G. M.; Nicoli, L.; Chen, Q.; Müllen, K.; Narita, A.; Lanzani, G.; Scotognella, F. Modulation of the Nonlinear Optical Properties of Dibenzo[hi,st]ovalene by Peripheral Substituents. J. Phys. Chem. C 2018, 122, 25007– 25013, DOI: 10.1021/acs.jpcc.8b06536[ACS Full Text], [CAS], Google Scholar22bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvV2js7jE&md5=ad5cb86ee8b3bbe833f491e3372dbeceModulation of the Nonlinear Optical Properties of Dibenzo[hi,st]ovalene by Peripheral SubstituentsPaterno, Giuseppe M.; Nicoli, Luca; Chen, Qiang; Mullen, Klaus; Narita, Akimitsu; Lanzani, Guglielmo; Scotognella, FrancescoJournal of Physical Chemistry C (2018), 122 (43), 25007-25013CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Dibenzo[hi,st]ovalene (DBOV) is a nanographene mol. with quasi-zero dimensional electronic confinement that displays relatively high oscillator strength, remarkable photostability, and optical gain property. For these reasons, DBOV has been proposed as a gain medium and active material for achieving strong exciton-photon coupling in microcavities. Here, we study the stimulated emission properties of three DBOV derivs. with different substitution patterns. We found that these mols. likely undergo ultrafast intermol. charge-transfer processes occurring within their π-aggregates, which ultimately leads to quenching of stimulated emission and increase of the amplified spontaneous emission threshold. These effects can be minimized by installing bulky substituents on the peripheries that prevent π-π stacking. Thus, by engineering the side groups, we can selectively favor either the luminescence/gain properties or the charge-transport features.
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