Time-Resolved Femtosecond Stimulated Raman Spectra and DFT Anharmonic Vibrational Analysis of an Electronically Excited Rhenium Photosensitizer

0522634 - ÚFCH JH 2021 RIV US eng J - Článek v odborném periodiku
Pižl, Martin - Picchiotti, Alessandra - Rebarz, Mateusz - Lenngren, Nils - Yingliang, Liu - Záliš, Stanislav - Kloz, Miroslav - Vlček, Antonín
Time-Resolved Femtosecond Stimulated Raman Spectra and DFT Anharmonic Vibrational Analysis of an Electronically Excited Rhenium Photosensitizer.
Journal of Physical Chemistry A. Roč. 124, č. 7 (2020), s. 1253-1265. ISSN 1089-5639. E-ISSN 1520-5215
Grant CEP: GA ČR GA17-01137S; GA MŠMT EF15_003/0000447; GA MŠMT EF16_019/0000789
Výzkumná infrastruktura: ELI Beamlines III - 90141
Institucionální podpora: RVO:61388955 ; RVO:68378271 ; RVO:86652036
Klíčová slova: Rhenium Photosensitizer * Raman Spectra * vibrational spectroscopic methods
Obor OECD: Physical chemistry; Physical chemistry (BTO-N); Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) (FZU-D)
Impakt faktor: 2.781, rok: 2020
Způsob publikování: Omezený přístup

Time-resolved femtosecond stimulated Raman spectra (FSRS) of a prototypical organometallic photosensitizer/photocatalyst ReCl(CO)3(2,2′-bipyridine) were measured in a broad spectral range ∼40–2000 (4000) cm–1 at time delays from 40 fs to 4 ns after 400 nm excitation of the lowest allowed electronic transition. Theoretical ground- and excited-state Raman spectra were obtained by anharmonic vibrational analysis using second-order vibrational perturbation theory on vibrations calculated by harmonic approximation at density functional theory-optimized structures. A good match with anharmonically calculated vibrational frequencies allowed for assigning experimental Raman features to particular vibrations. Observed frequency shifts upon excitation (ν(ReCl) and ν(CC inter-ring) vibrations upward, ν(CC, CN) and ν(Re–C) downward) are consistent with the bonding/antibonding characters of the highest occupied molecular orbital and the lowest unoccupied molecular orbital involved in excitation and support the delocalized formulation of the lowest triplet state as ReCl(CO)3 → bpy charge transfer. FSRS spectra show a mode-specific temporal evolution, providing insights into the intersystem crossing (ISC) mechanism and subsequent relaxation. Most of the Raman features are present at ∼40 fs and exhibit small shifts and intensity changes with time. The 1450–1600 cm–1 group of bands due to CC, CN, and CC(inter-ring) stretching vibrations undergoes extensive restructuring between 40 and ∼150 fs, followed by frequency upshifts and a biexponential (0.38, 21 ps) area growth, indicating progressing charge separation in the course of the formation and relaxation of the lowest triplet state. Early (40–150 fs) restructuring was also observed in the low-frequency range for ν(Re–Cl) and δ(Re–C–O) vibrations that are presumably activated by ISC. FSRS experimental innovations employed to measure low- and high-energy Raman features simultaneously are described and discussed in detail.
Trvalý link: http://hdl.handle.net/11104/0307098