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.