Two Isomers of a Cyanostilbene Derivative in Viscous Solution Observed by Fluorescence Spectroscopy

1-Cyano-trans-1,2-bis(4′-methylbiphenyl)ethylene (CN-MBE) is a prototypical molecule that exhibits aggregation-induced emission (AIE); however, there is very little information about its molecular structure. Viscosity-dependence of fluorescence excitation and fluorescence spectra, fluorescence quantum yield, and fluorescence lifetime were recorded for CN-MBE in an EtOH/glycerin mixed solution. The experimental results indicate that S1→S0 fluorescence arises from the twisted and (near) planar structures.