Theoretical and experimental study of cyano- and alkoxy-substituted phenylenevinylene model compounds

We present a theoretical and experimental investigation of methoxy- and cyano-substituted p-phenylenevinylene model compounds. The compound containing both the alkoxy and cyano substitution exhibits a drop in the quantum yield relative to the singly-substituted alkoxy or alkyl compounds. In addition the emission spectrum loses structure and shifts to the red. Model calculations are performed on the chromophore and ab-initio CIS calculations show that the first excited state HOMO to LUMO transition is delocalised in methoxy-substituted compounds and localised on methoxy- and cyano-substituted compounds.