The Effect of Cyano Substitution on the Fluorescence Behavior of 1,2-Bis(pyridylphenyl)ethene

The effect of cyano substitution on the fluorescence behavior of 1,2-bis(pyridylphenyl)ethene was investigated. While nonsubstituted 1,2-bis(pyridylphenyl)ethene has fluorescence quantum yield of 97 % in CH2Cl2 solution, cyano-substituted ones fluoresces very little. In contrast, both the no-substituted and the cyano-substituted ones fluoresce moderately in the solid state. The aggregate-induced enhanced emission (AIEE) behavior for the cyano-substituted 1,2-bis(pyridylphenyl)ethene was understood as that the severe quenching of the fluorescence in solution was not operating in the solid state. The fluorescent behaviors in solution and in the solid state are discussed in terms of the emission and the nonradiative decay rate constants.