The influence of solvent dielectric constant on the photophysical properties of cyano and alkoxy substituted phenylene vinylene model compounds

We report time-resolved and steady-state photoluminescence studies of three substituted phenylene vinylene model compounds in solvents of different dielectric constant. We note that the compound containing both the alkoxy and cyano substitution exhibits a drop in the quantum yield relative to the monosubstituted alkoxy or alkyl compounds. In addition, the emission spectrum loses structure and shifts to the red in high dielectric constant solvent. Estimates of the non-radiative lifetime of the emitting species in this model compound are markedly longer and we interpret this as an indication that the emitting state has a high degree of charge-transfer character.