Estudo fotoquímico por fotólise por pulso de laser em nanossegundo de tioxantona

Abstract

This work had as objective the determination of the rate constants for quenching of triplet state excited of Thioxanthone by hydrogen, electron and energy donors, being by the nanossecond laser flash photolysis technique in Acetonitrile solution. Also were studied its behavior in solvents of differents polarities. The substance produced in commercial scale and, for exemple, is a photoinitiator in photopolymerization reactions. The study of its photochemistry reactions with differents quencchers is necessary to analysis of possible transients. The obtained results show rate constants of reaction are of the order of (1,98 ± 0,04) x 1010 to (1,96 ± 0,04) x 105 L. mol-1, that depends on the process involved in the suppression reaction: energy, electron transfer or abstraction of hydrogen. Preliminary analyses demonstrate that the state excited triplet of lower energy of Thioxanthone presents a character nπ*, in other words, there is no inversion of states triplet, although it is still necessary to accomplish other experiments for this confirmation