GROUND AND EXCITED SINGLET-STATES OF 2-VINYLNAPHTALENE, ETHYL-2-NAPHTHYLACRYLATE AND N,N-DIMETHYL-2-NAPHTHYLACRYLAMIDE IN SOLUTION

The molecular conformation, spectroscopy and photochemical behavior of 2-vinylnaphthalene and its acrylate and acrylamide analogs were inves tigated. All three molecules exist as mixtures of syn and anti conform ers. Ground state conformer populations were studied by nuclear Overha user effect (NOE) spectroscopy and MM2 calculations. The electronic st ructure and spectra of the syn and anti conformers were investigated b y INDO/S-SCF-CI calculations and were found to be very similar. Dual e xponential fluorescence decay is observed for these molecules and is a ttributed to fluorescence from both the syn and anti conformers. The a bsence of a wavelength dependence for the fluorescence excitation and emission spectra provides experimental evidence that the syn and anti conformers have similar spectra. Photoisomerization of the acrylate an d acrylamide occurs via a triplet state mechanism. Quenching of the ac rylate singlet states by amines is more rapid for the syn relative to the anti conformer. Quenching by secondary and tertiary amines results in the regioselective formation of N-H and alpha-C-H adducts respecti vely. The quantum yields of photoisomerization and photoaddition were determined for a mixture of the conformers, but were not separated int o values for the individual conformers. The spectroscopy and photochem istry of ethyl-1-naphthylacrylate, which exists as a single conformer, were also investigated.