STYRYLPYRIDINE AMINE EXCIPLEXES - SUBSTITUENT EFFECTS

Fluorescent exciplexes were observed between excited para-substituted trans-styrylpyridines (n-StP, n = 2,3,4 and X = CN, Cl, H, (CH3)2CH, C H3, CH3O) and three tertiary amines, (i.e. diisopropyl ethylamine, tri butylamine and triethylamine) in n-hexane at room temperature. The exc iplex emission for the 2-StP-amine system was extremely weak. The maxi mum fluorescence energies were correlated with the values of Rehm and Weller, except for those for the StP with cyano groups. There was bett er correlation when a stronger electron-donating amine was used. The q uenching rate constants increase as DELTAG0 for electron transfer beco mes more exergonic, except for the case of cyano derivatives. The exci plex fluorescent energies also showed a linear correlation with the Ha mmett sigma(p) constants, again except for the cyano derivatives. The calculated dipole moments for the styrylpyridine-amine exciplexes are larger than those for stilbene-amine exciplex systems.