Unveiling electronic transitions in three novel chiral azo-compounds using linear and nonlinear circular dichroism: a theoretical-experimental study.

Herein, we report on the experimental and theoretically study of the linear absorption, electronic circular dichroism (ECD) spectra, as well as the two-photon absorption circular−linear dichroism measurements of three different chiral azo derivatives in dimethylsulfoxide solution. Using potential energy surfaces and frontier orbital analysis, we established the most stable conformation for each molecule and elucidated their different electronic transitions. Our theoretical calculations allowed us to unambiguously identify the spectral position of such transitions and correlate them with the spectral profiles observed in the two-photon absorption spectra. To further elucidate the characteristics of the main electronic transitions in terms of spectral shape and position, we carried out measurements of the polarization dependent two-photon absorption cross sections and determined the two-photon circular−linear dichroism spectra of these azo dyes.