Hydrogen bond studies in thermochromic and photochromic N-salicylidene anilines

Abstract

Using nuclear quadrupole resonance and nuclear quadrupole double resonance techniques, the temperature dependence of 35Cl, 14N and 17O frequencies have been measured in some photochromic and thermochromic solid N-salicylidene anilines. The results are compatible with a model where thermochromism and photochromism are accompanied by a fast intramolecular proton transfer in the O H⋯N bond resulting in an enol-keto transformation. This exchange is reflected in the temperature dependence of the 17O and 14N electric field gradient tensors.