EXCITED-STATE REACTIVITY OF AZA-AROMATICS .7. PRODUCTION AND QUENCHING OF TRIPLET NAPHTHYLPYRIDYLETHYLENE INDUCED BY HALIDE ANIONS

The effect of alkali halides on the fluorescence and trans → cis photoisomerization of 1-(β-naphthyl),2-(4-pyridyl)ethylene in the protonated form has been investigated. The results are compared with those obtained for azastilbenes. In contrast to the effect observed for the latter compounds, both the fluorescence and photoisomerization quenching efficiency follow the order of the oxidation potentials of the anions (Cl- < Br- < I-). With the weaker perturber, the photoreaction is enhanced by induction of S1 → T1 intersystem crossing. In the case of the heavier perturbers, the parallel induction of T1 → S0 intersystem crossing leads to a reduction of the overall reaction yield. The analysis of the results obtained gives information on the inherent properties of the excited naphthylpyridylethylenes. © 1979.