Styrylthiophene-amine exciplexes

The reductive fluorescence quenching of para-substituted-trans-3-styrylthiophene (X=OCH3, CH3, CH(CH3)(2), H, F, Cl, Br, CN) by tertiary amines (triethylamine TEA, diisopropylethylamine DIPEA, diisopropylmethylamine DIPMA) were studied in both polar and nonpolar solvents. Stern-Volmer quenching constants increase with both increasing electron-withdrawing ability of the acceptor and electron-donating ability of the donor and were higher in acetonitrile than in nonpolar solvents. Twenty-four fluorescent exciplexes were observed between excited styrylthiophene and tertiary amines in nonpolar solvents at room temperature. The transition energies of the exciplex maximum fluorescence were correlated with the Rehm and Weller values. Better correlation with those exciplexes which have larger enthalpies of dissociation is observed. The transition energies of the exciplexes give linear correlation with Hammett a, constant. The dipole moments obtained from the Lippert equation were larger for the triethylamine systems.