NANOSECOND TIME-RESOLVED RESONANCE RAMAN INVESTIGATION OF THE RADICAL-CATION OF 4,4'-DIBROMOBIPHENYL AND THE T-1 -] T-N TRANSITION OF 4,4'-DIBROMOBIPHENYL

We have taken nanosecond time-resolved resonance Raman spectra of the T-1 --> T-n, transition of 4,4'-dibromobiphenyl in cyclohexane solutio n and of the radical cation of 4, 4'-dibromobiphenyl in acetonitrile s olution. The resonance Raman spectrum of T-1 4,4'-dibromobiphenyl is c onsistent with a planar quinoidal structure. The C-Br bond appears str onger in the T-1 state than in the S-0 ground state and this is in agr eement with photochemistry studies done for 4-bromobiphenyl that indic ate that the T-1 state must be further excited by excimer formation an d/or electron transfer with an appropriate donor prior to a debrominat ion reaction. (C) 1998 Published by Elsevier Science B.V. All rights r eserved.