Journal of Physical Chemistry, Vol.99, No.19, 7246-7250, 1995
Resonance Raman Characterization of the Triplet-State of Zinc Tetraphenylchlorin
The T-1 excited state of zinc(II) tetraphenylchlorin, ZnTPC, has been studied by nanosecond time-resolved transient absorption (TA) and transient resonance Raman (TR(3)) spectroscopy. The TA difference spectrum shows an induced absorption at 450 nm that is assigned as arising from a (3)(pi,pi*) state. The most striking feature of the (3)(ZnTPC) TR(3) spectrum is the significant frequency downshifts and strong intensity enhancements of the pyrrole half-ring stretch, nu(4), and of other pyrrole ring motions which together produce a broad band in the 1150-1300-cm(-1) region. In addition, the enhancement of CalphaCm modes (nu 2 and nu(11)) changes with their phasing between the S-0 and T-1 states. Weaker intensity enhancements, with no frequency shifts, are seen for the phenyl substituent ring mode, Phi(4) and nu(1), and C-m-phenyl stretch. These findings suggest that there is less electronic participation from the phenyl rings in the resonant triplet state, T-n, for ZnTPC than for its parent metalloporphyrin, ZnTPP.
Keywords:DISSIMILATORY NITRITE REDUCTASE;EXCITED-STATES;PROSTHETIC GROUP;MODEL COMPOUNDS;SPECTRA;SPECTROSCOPY;PORPHYRINS;TETRAPHENYLPORPHINE;OCTAETHYLPORPHYRIN;METALLOPORPHYRINS