Formation and anomalous behavior of aminonaphthalene-cinnamonitrile exciplexes

dThe solvent dependence of the electronic spectra of several 1-aminonaphtha lenes and 2-aminonaphthalenes in the absence and presence of two styrene de rivatives, cinnamonitrile and 1-phenylpropene, has been investigated. The a bsorption maxima of the aminonaphthalenes are dependent upon both the polar ity and hydrogen-bond donor and acceptor properties of the solvent and disp lay both red and blue solvent shifts. The fluorescence maxima are more sens itive to solvent polarity than are the absorption maxima and display red sh ifts in both non-hydroxylic and hydroxylic solvents. The excited state dipo le moments of the l-aminonaphthalenes are larger than those of the 2-aminon aphthalenes, Quenching of the aminonaphthalene fluorescence by cinnamonitri le occurs with diffusion-controlled rates in all solvents, in accord with t he occurrence of exergonic electron transfer. Exciplex fluorescence is obse rved only for the tertiary aminonaphthalenes in nonpolar solvents. The exci plex fluorescence displays anomalous temperature dependence in hexane solut ion, an increase in temperature resulting in blue-shifted exciplex fluoresc ence and an increase in the exciplex decay time. Quenching of the aminonaph thalene fluorescence by 1-phenylpropene is slower than diffusion controlled and is not accompanied by exciplex fluorescence.