The triplet state decay kinetics and deactivation funnel geometry of a series of nonplanar saddle-shaped porphyrins

Abstract

It is found that the triplet state lifetimes of the series of nonplanar saddle-shaped porphyrins are much shorter than those of their planar analogs (hundreds of nanoseconds vs. several milliseconds). As our calculations show, two low-lying conformations with strongly different triplet-ground singlet state energy gap Δ E TS exist for each molecule in its triplet state. An energy inversion of these conformations for the most distorted porphyrin molecule is found to be responsible for the observed non-monotonic dependence of the triplet state deactivation rate on the degree of nonplanar distortion.