Luminescent Iridium Complexes with a Sulfurated Bipyridine Ligand: PCET Thermochemistry of the Disulfide Unit and Photophysical Properties
- Manuel OelschlegelManuel OelschlegelInstitute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, GermanyMore by Manuel Oelschlegel
- ,
- Shao-An HuaShao-An HuaInstitute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, GermanyMore by Shao-An Hua
- ,
- Lucius SchmidLucius SchmidDepartment of Chemistry, University of Basel, CH-4056Basel, SwitzerlandMore by Lucius Schmid
- ,
- Philipp MarquetandPhilipp MarquetandInstitute of Theoretical Chemistry, University of Vienna, Währingerstraße 17, A-1090 Vienna, AustriaMore by Philipp Marquetand
- ,
- Anna BäckAnna BäckInstitute of Theoretical Chemistry, University of Vienna, Währingerstraße 17, A-1090 Vienna, AustriaMore by Anna Bäck
- ,
- Jan-Hendrik BorterJan-Hendrik BorterDepartment of Dynamics at Surfaces, Max-Planck-Institute for Multidisciplinary Sciences, Am Faßberg 11, D-37077 Göttingen, GermanyMore by Jan-Hendrik Borter
- ,
- Jana LückenJana LückenInstitute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, GermanyMore by Jana Lücken
- ,
- Sebastian DechertSebastian DechertInstitute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, GermanyMore by Sebastian Dechert
- ,
- Oliver S. WengerOliver S. WengerDepartment of Chemistry, University of Basel, CH-4056Basel, SwitzerlandMore by Oliver S. Wenger
- ,
- Inke SiewertInke SiewertInstitute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, GermanyInstitute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, GermanyMore by Inke Siewert
- ,
- Dirk Schwarzer*Dirk Schwarzer*Email: [email protected]Department of Dynamics at Surfaces, Max-Planck-Institute for Multidisciplinary Sciences, Am Faßberg 11, D-37077 Göttingen, GermanyMore by Dirk Schwarzer
- ,
- Leticia González*Leticia González*Email: [email protected]Institute of Theoretical Chemistry, University of Vienna, Währingerstraße 17, A-1090 Vienna, AustriaMore by Leticia González
- , and
- Franc Meyer*Franc Meyer*Email: [email protected]Institute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, GermanyInternational Center for Advanced Studies of Energy Conversion (ICASEC), D-37077 Göttingen, GermanyMore by Franc Meyer
Abstract
Molecular systems combining light harvesting and charge storage are receiving great attention in the context of, for example, artificial photosynthesis and solar fuel generation. As part of ongoing efforts to develop new concepts for photoinduced proton-coupled electron transfer (PCET) reactivities, we report a cyclometallated iridium(III) complex [Ir(ppy)2(S–Sbpy)](PF6) ([1]PF6) equipped with our previously developed sulfurated bipyridine ligand S–Sbpy. A new one-step synthetic protocol for S–Sbpy is developed, starting from commercially available 2,2′-bipyridine, which significantly facilitates the use of this ligand. [1]+ features a two-electron reduction with potential inversion (|E1| > |E2|) at moderate potentials (E1 = −1.12, E2 = −1.11 V versus. Fc+/0 at 253 K), leading to a dithiolate species [1]–. Protonation with weak acids allows for determination of pKa = 23.5 in MeCN for the S–H···S– unit of [1H]. The driving forces for both the H atom and the hydride transfer are calculated to be ∼60 kcal mol–1 and verified experimentally by reaction with a suitable H atom and a hydride acceptor, demonstrating the ability of [1]+ to serve as a versatile PCET reagent, albeit with limited thermal stability. In MeCN solution, an orange emission for [1]PF6 from a triplet-excited state was found. Density functional calculations and ultrafast absorption spectroscopy are used to give insight into the excited-state dynamics of the complex and suggest a significantly stretched S–S bond for the lowest triplet-state T1. The structural responsiveness of the disulfide unit is proposed to open an effective relaxation channel toward the ground state, explaining the unexpectedly short lifetime of [1]+. These insights as well as the quantitative ground-state thermochemistry data provide valuable information for the use of S–Sbpy-functionalized complexes and their disulfide-/dithiol-directed PCET reactivity.
Cited By
This article has not yet been cited by other publications.