Picosecond transient resonance Raman study on the excited-state conformational dynamics of a highly ruffled nickel porphyrin

Picosecond to nanosecond transient resonance Raman spectroscopy was applied to track down the excited-state conformational excursions of (NiT)-T-II(t- Bu)P [nickel(II) 5,10,15,20-tetra-tert-butylporphyrinl in various solvents with different dielectric properties. From the resonance Raman spectra of ( NiT)-T-II(t-Bu)P obtained by picosecond pulse photoexcitation, the alpha (4 )-type conformer was suggested to be dominant in the (1)(d,d) excited state at the initial stage of deactivation processes (similar to3 ps). However, only one conformer of alpha beta alpha beta type was found to persist on th e nanosecond time-scale. We also observed that the initial formation of the (1)(d,d) excited state of (NiT)-T-II(t-Bu)P from the (1)(pi,pi*) excited s tate is independent of the solvent, but the subsequent decay of the (1)(d,d ) to the ground state is strongly solvent dependent. Copyright (C) 2001 Joh n Wiley & Sons, Ltd.