Effect of the nitrogen heteroatom on the photophysics and photochemistry of trans‐1‐styrylnaphthalene and trans‐9‐styrylphenanthrene in different solvents

Abstract

The effect of the nitrogen heteroatom on the excited state properties of trans‐1‐styryl‐naphthalene (1‐StN) and trans‐9‐styrylphenanthrene (9‐StPh) has been investigated by fluorimetric and photochemical techniques. The relaxation processes of two aza analogues of each of these diarylethylenes, bearing the nitrogen atom in the mono‐ and polycyclic aryl group, respectively, were studied in different solvents and over a large temperature range. The aza derivatives have smaller radiative and large reactive decay yields compared with the parent hydrocarbons. The polar solvent reduces the torsional energy barrier and favours the trans → cis photoisomerization while intramolecular hydrogen bonding may slow down the rate of the reactive deactivation. Copyright © 1995 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim