Isomerism in jet-cooled 1-cyanonaphthalene complexes

Abstract

The effect of complexation on the first electronic transition of 1-cyanonaphthalene has been studied for complexes with aprotic polar solvents (acetonitrile, diethylether) or olefins (2-methyl-2-butene, 2,3-dimethyl-2-butene). In both cases, isomerism has been evidenced.

With polar solvents, two strong absorption bands appear in the 0 ⁰₀ region, one being shifted to the red and the other one to the blue side of the bare cyanonaphthalene transition. These two bands have been assigned to two isomeric forms involving specific interactions between the solvent and the cyanonaphthalene molecule. These isomers have been shown to interconvert at higher vibronic energies.

With the 2,3-dimethyl-2-butene a broad absorption band leading to a red shifted fluorescence has been observed and assigned to an exciplex. With the 2-methyl-2-butene, one observes the superposition of narrow and broad bands in the excitation spectrum. These two systems have been assigned to two isomeric forms, one of them crossing to an exciplex in the excited state. At higher vibronic energy, emission from the two conformers is observed.