PIEZOCHROMISM OF N-SALICYLIDENE AMINOPYRIDINES IN POLYMERIC MATRICES

In this paper we present data on the pressure induced isomerization of N-salicylidene-x-aminopyridine (x = 2, 3, 4), from the enol form to cis-keto forms. The studies took place in polymeric matrices. The conversion was independent of concentration in the polymer and of the value of x. It varied only slightly with the polymeric medium. The process indicates a lowering of the energy barrier between the two ground electronic states upon compression, and is primarily an intramolecular one. A decrease in conversion with time at a given pressure was noted. This effect decreased rapidly with increasing pressure. Evidently a mechanical relaxation of the environment can effect the chemical equilibrium.