Solvent effects in the photoisomerization of phenazine 5-oxide
Abstract
The photoisomerization of phenazine 5-oxide in acetonitrile–water mixtures has been investigated. The quantum yields of 10H-azepino[1,2-a]benzimidazol-10-one (3) and 2-(4-cyanobuta-1,3-dienyl)benzoxazole (4) are closely related to solvent composition in that they decrease strongly with increasing content of water. In acetonitrile ϕ3 and ϕ4 are temperature independent. The quantum yield of oxepino[2,3-b]quinoxaline (5) is almost independent of the composition of the solvent mixtures. A mechanism is proposed which relates the quantum yield variations to the properties of the excited state.