Influence of Steric Effects on the Excited Triplet-State Lifetime of 2,2'-Dinitrostilbene and 2,2',4,4',6,6'-Hexanitrostilbene in Acetonitrile Solution

Article abstract of DOI:10.1021/j100195a010

Solutions of 4,4'-dinitrostilbene, 2,2'-dinitrostilbene, 2,2',4,4',6,6'-hexanitrostilbene (HNS), and deuterated derivatives of HNS in acetonitrile have been studied by laser flash photolysis.Transient species with decay lifetimes of 125, 55, and 21 ns, respectively, were observed for the nondeuterated compounds.The decay lifetimes for these species provide evidence that the excited triplet-state lifetime is being reduced as steric hindrance to molecular planarity is increased.This is partly attributed to a reduction in the S₀-T₁ energy gap of the perpendicular configuration with increasing intramolecular steric hindrance although, for HNS, rapid formation of photoproducts also occurs.The degree of intramolecular steric hindrance associated with nitro groups ortho to the central double bond is indicated by singlet ground-state absorption measurements.