TWO HETEROCYCLIC MEROCYANINE CLASSES AND THEIR OPTICAL PROPERTIES IN RELATION TO THE DONOR-ACCEPTOR STRENGTH OF END SUBSTITUENTS
Keywords:heterocyclic merocyanines, cyanine limit, donor-acceptor strength, first electronic transition, graphical hyperbolic model
The relationship between the first electronic transition energy of heterocyclic merocyanines and donor-acceptor properties of their end substituents has been quailtatively treated and analytically substantiated in terms of the classical valence bond model and the biradicaloid theory. A simple graphical technique has been suggested to classify donor-acceptor-substituted compounds in relation to their electronic structure and to predict the effect of donor-acceptor strength on their optical behavior. In this context, merocyanines can be divided into two classes which differ in charges and electron populations of their donor and acceptor moieties and exhibit mirror-like responses to the variation of donor-acceptor strength. Two families of new heterocyclic merocyanines have been synthesized and their experimentally observed spectroscopic properties have been rationalized using the approach developed.
Also published in Chemistry of Heterocyclic Compounds, 2011, 47 (10), pp 1244-1257