Time-resolved electron paramagnetic resonance study of the lowest excited triplet states of trans-cinnamic acid and trans-cinnamate anion

Abstract

Time-resolved and steady-state electron paramagnetic resonance spectra have been observed for the lowest excited triplet (T 1) states of trans-cinnamic acid (RCOOH) and trans-cinnamate anion (RCOO −) in methanol-water and in stretched poly(vinyl alcohol) films at 77 K. The zero-field splitting parameters | D| and | E| in the T 1 state slightly increase on deprotonation. The sublevel preferentially populated by intersystem crossing in T y in RCOOH, while the in-plane T x and T y sublevels are prefentially populated in RCOO − (the x and y axes are close to the long and short in-plane molecular axis, respectively).