Quantification of Push-Pull Character of Azo Dyes and a Basis for Their Evaluation as Potential Nonlinear Optical Materials

Abstract

The push–pull character of a series of para-phenyl substituted isophorone chromophores has been quantified by the 13C chemical shift difference of the three conjugated partial Cdouble bond; length as m-dashC double bonds and the quotient of the occupations of both the bonding and anti-bonding orbitals of these Cdouble bond; length as m-dashC double bonds as well. The correlations of the two push–pull quantifying parameters, and to the corresponding bond lengths, strongly recommend View the MathML sourceπCC∗/πCdouble bond; length as m-dashC as the general parameter to estimate charge alternation and as a very useful indication of the molecular hyperpolarizabilities for NLO application of the compounds studied