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 Ni II T( t ‐Bu)P [nickel(II) 5,10,15,20‐tetra‐ tert ‐butylporphyrin] in various solvents with different dielectric properties. From the resonance Raman spectra of Ni II T( t ‐Bu)P obtained by picosecond pulse photoexcitation, the α 4 ‐type conformer was suggested to be dominant in the 1 (d,d) excited state at the initial stage of deactivation processes (∼3 ps). However, only one conformer of αβαβ type was found to persist on the nanosecond time‐scale. We also observed that the initial formation of the 1 (d,d) excited state of Ni II T( t ‐Bu)P from the 1 (π,π*) excited state is independent of the solvent, but the subsequent decay of the 1 (d,d) to the ground state is strongly solvent dependent. Copyright © 2001 John Wiley & Sons, Ltd.