Nature of excited singlet and non-phosphorescent triplet states of perinaphthenone

Natures of excited singlet and triplet states of perinaphthenone (PPS) were investigated. Assignment of low-lying excited states was carried out by el ectronic spectra and CNDO/S-CI molecular orbital calculation. No phosphores cence was observed and an emission reported as phosphorescence was assigned to the emission of PN ketyl radical. Tripler energy and electronic nature of the lowest triplet state were determined by the time-resolved thermal le nsing (TRTL) and the time-resolved ESR experiments. The triplet energy was determined to be 164 kJ mol(-1) and the ZFS parameters were determined to b e 0.075 and 0.014 cm(-1) for \D\ and \E\ values, respectively. \D\ value of PN indicates that the electronic nature of the triplet state is pi pi*. A liner relationship was confirmed between the triplet energy and the \D\ val ue. The triplet energy and D value of PN satisfy this relationship. (C) 200 0 Elsevier Science S.A. All rights reserved.