Interactions of β-Naphthol and β-NaphthyIamine in Their Excited Singlet States with Triethylamine

Abstract

Abstract Proton donor-acceptor interactions in excited states were studied by measuring mainly time-resolved fluorescence spectra for β-naphthol–TEA in toluene and in acetonitrile, and for β-naphthylamine–TEA in nonpolar mixed solvents. The Stern-Volmer relation was found to be satisfied for β-naphthol–TEA in toluene. The rate constant and activation energy of hydrogen bond formation in the excited state of this system were obtained to be 2.2×109 M−1 s−1 at 30 °C and 1.6 kcal/mol, respectively, indicating that the process is diffusion-controlled. The time dependences of the intensities of the fluorescence bands due to the free and complexed β-naphthol were measured with the solutions containing various concentrations of triethylamine in acetonitrile. From the analysis of the result, it is shown that this system is led to the ion-pair formation via the hydrogen-bonded species in the excited state. For β-naphthylamine–TEA in nonpolar mixed solvents, the bands due to hydrogen-bonded species in the ground and excited states were observed at 370 and ∼390 nm in the absorption and fluorescence spectra, respectively.