Hemioxonol dyes

Abstract

Abstract Following the classification of hemicyanine dyes Leslie G. S. Brooker suggested the term hemioxonol dye be applied to the case of an oxonol colorant in which one of its terminal unsaturated heterocycles has been replaced by an open chain N(R1)R2 group or saturated heterocyclic ring. For historical reasons, dyes formed from the reaction of 4-N,N-dialkylaminobenzaldehydes or 4-N,N-dialkylaminocinnamaldehydes with a heterocycle containing an active methylene group adjacent to a carbonyl group are often called benzylidene dyes and cinnamylidene dyes, respectively. In terms of systematic nomenclature, their proper classification is as hemioxonol dyes. They are used as filter dyes and antihalation dyes in silver halide photography. Their current main usage is in dye diffusion thermal transfer printing (D2T2).