PHOTOSENSITIZATION VIA CHARGE TRANSFER OR REVERSIBLE ELECTRON TRANSFER. OXIRANE ISOMERIZATION AND SULFUR DIOXIDE EXTRUSION

Abstract

Abstract— N, N, N ′ N ′ ‐Tetramethylbenzidine (NTMB) photosensitizes the cis‐trans isomerization of stilbene oxiranes (SO) and the extrusion of SO 2 from dibenzyl sulfone (DBS). In acetonitrile solution it is found that in the absence of SO or DBS, singlet NTMB undergoes three processes: intersystem crossing to triplet NTMB (φ ISC = 0.63, k ISC = 6.3 × 10 7 s ‐1 ), fluorescence (φ f = 0.30, k f = 3 × 10 7 s ‐1 ), and formation of a cation by electron ejection (φ ion = 0.09). Both singlet and triplet sensitization are observed. A charge transfer or reversible electron transfer mechanism is proposed to explain the results.