Intramolecular charge-transfer fluorescence of 4-(4-cyano-1-naphthylmethylene)-1-phenylpiperidine in cyclohexane–methyl acetate binary mixtures and related aliphatic esters. Polarity vs. mobility control of the relaxation of a highly dipolar excited state
The charge transfer (CT) emissive behaviour of the dipolar excited state of 4-(4-cyano-1-naphthylmethylene)-1-phenylpiperidine and two of its derivatives, containing an alkyl chain at the para position of the dialkylanilino donor moiety is studied in cyclohexane–methyl acetate binary solvent mixtures and structurally related liquid and solid aliphatic esters. In the liquid matrices, changes of the CT emission maximum can be related to stabilization of the dipolar excited state by the polarity of the matrix sites, which accommodate the probe molecule. However, in solid matrices, the relaxation behaviour of the dipolar excited state is affected mainly by the mobility of the matrix sites.