We have taken nanosecond time-resolved resonance Raman spectra of the T1→Tn transition of 4,4′-dibromobiphenyl in cyclohexane solution and of the radical cation of 4,4′-dibromobiphenyl in ...acetonitrile solution. The resonance Raman spectrum of T1 4,4′-dibromobiphenyl is consistent with a planar quinoidal structure. The C–Br bond appears stronger in the T1 state than in the S0 ground state and this is in agreement with photochemistry studies done for 4-bromobiphenyl that indicate that the T1 state must be further excited by excimer formation and/or electron transfer with an appropriate donor prior to a debromination reaction.
Resonance Raman spectra including absolute Raman cross-section measurements and density functional theory (DFT) calculations were performed to study the A-band absorption of C
5H
5WCCPhO
2. The ...three most intense Franck–Condon active modes, the nominal WO stretch, CC stretch and CC stretch, show noticeable intensity in their overtones as well as their combination bands with each other. This is consistent with the changes in the HOMO–LUMO electron densities obtained from the DFT calculations. This suggests that the excited-state experiences significant structural changes simultaneously in the WO, CC and CC groups and the charge transfer is delocalized in the electronic transition.
Resonance Raman and preresonance Raman spectra of chloroiodomethane in cyclohexane solution have been obtained at excitation wavelengths of 282, 309, 320, 342, 355, and 532 nm. The 282 nm spectrum is ...in resonance with the directly dissociative A-state absorption band of chloroiodomethane. We observe a large degree of Raman intensity in the C-1 stretch overtone progression as well as combination bands of the C-Cl stretch mode with the C-1 stretch overtones indicating that most of the initial photodissociation dynamics in the Franck-Condon region involves the C-1 stretch motion as well as some C-Cl stretch motion.
