The solvent dependence of the electronic spectra of several 1-aminonaphthalenes and 2-aminonaphthalenes in the absence and presence of two styrene derivatives, cinnamonitrile and 1-phenylpropene, has been investigated. The absorption maxima of the aminonaphthalenes are dependent upon both the polarity and hydrogen-bond donor and acceptor properties of the solvent and display both red and blue solvent shifts. The fluorescence maxima are more sensitive to solvent polarity than are the absorption maxima and display red shifts in both non-hydroxylic and hydroxylic solvents. The excited state dipole moments of the 1-aminonaphthalenes are larger than those of the 2-aminonaphthalenes. Quenching of the aminonaphthalene fluorescence by cinnamonitrile occurs with diffusion-controlled rates in all solvents, in accord with the occurrence of exergonic electron transfer. Exciplex fluorescence is observed only for the tertiary aminonaphthalenes in nonpolar solvents. The exciplex fluorescence displays anomalous temperature dependence in hexane solution, an increase in temperature resulting in blue-shifted exciplex fluorescence and an increase in the exciplex decay time. Quenching of the aminonaphthalene fluorescence by 1-phenylpropene is slower than diffusioncontrolled and is not accompanied by exciplex fluorescence.Aromatic amines are strong electron donors that have been widely employed in investigations of exciplex formation and photoinduced electron transfer. [1][2][3][4][5] In most such studies, ground state N,N-dialkylanilines have been used to quench relatively nonpolar singlet acceptors. Since the exciplex or contact ion pair formed in such reactions is more polar than the locally excited singlet state, solvent polarity has a pronounced effect on exciplex formation and behavior. Increasing solvent polarity has little effect on the fluorescence of the locally excited singlet but causes a red shift in the exciplex emission and a decrease in the exciplex fluorescence intensity and lifetime due increased rates of nonradiative decay or ionic dissociation. The formation of fluorescent exciplexes has been observed for N,N-dialkylanilines but not for primary or secondary anilines. 2 The absence of exciplex fluorescence from exciplexes formed by secondary and tertiary anilines has been attributed to proton transfer processes and enhanced intersystem crossing. 2,5 Quenching of singlet aromatic amines by ground state acceptors can also result in electron transfer. [6][7][8][9][10][11] In comparison to the quenching of singlet acceptors by aromatic amines, quenching of singlet aromatic amines by ground state acceptors has received limited attention. Beens and Weller 1a noted the failure of dimethylaniline and benzene to form an exciplex and suggested that it might be a consequence of limited orbital overlap. Intermolecular exciplex formation upon quenching of 2-dimethylaminonaphthalene by dimethylphthalates in nonpolar solvents was observed by Kaneta and Kiozumi. 6 Fluorescence