Photodissociation of Hexaarylbiimidazole. 1. Triplet-State Formation

Article abstract of DOI:10.1021/j100168a022

The mechanism of photodissociation of 2-chlorohexaarylbiimidazole is studied by laser flash photolysis in organic liquids and by EPR methods in polymer and low-molecular-weight organic matrices.It is found that at low temperature (ca. 10 K) the ultraviolet irradiation produces a triplet hexaarylbiimidazole rather than the radicals.No triplet-state decomposition into radicals is observed, supporting the results of indirect measurements reported by other researchers.At higher temperatures, the radicals formed from the dissociation of the singlet state dominate.This is the first direct observation of the hexaarylbiimidazole triplet reported to date.The results are explained by considering the molecular structure and hexaarylbiimidazole mobility.