Pulse radiolysis and DFT investigation of a one-way photochromic diarylethene in solution: Observation of triplet-triplet absorption

Abstract

Pulse radiolysis studies of a diarylethene (PTSO₂) that shows only ring-closing photochromism were performed in toluene to form the triplet state. Radiolysis of the ring-opened PTSO₂ (o-PTSO₂) in toluene achieved the triplet sensitization by observing the triplet-triplet (T-T) absorption at 520 nm without ring-closing reaction to the corresponding ring-closed PTSO₂ (c-PTSO₂). Conversely, radiolysis of c-PTSO₂ also showed the T-T absorption at 520 nm with an unidentified absorption band at 600 nm. It was unable to confirm the ring-opening reaction to o-PTSO₂ in triplet c-PTSO_2. The lifetimes of the triplets and the unknown intermediates were determined. Based on DFT calculations, T-T absorption spectra for o- and c-PTSO₂s were simulated, which agreed with those obtained experimentally.