Inspired by a previous experimental study on the
first-order hyperpolarizabilities of 1,3-thiazolium-5-thiolates mesoionic
compounds using Hyper-Rayleigh scattering technique, we
theoretically investigated the UV-Vis absorption spectra and every order polarizabilities
of these mesoionic molecules. Based on the fact that the photophysical and
nonlinear properties observed in the experiment can be perfectly replicated,
our theoretical calculations explored the essential characteristics of the
optical properties of the mesoionic compounds
with different electron-donating groups at the level of electronic structures
through various wave function analysis methods. The influence of the
electron-donating ability of the donor on the optical properties of the
molecules and the contribution of the mesoionic ring moiety to their optical
nonlinearity are clarified, which have not been reported by any research so
far. This work will help people understand the nature of optical properties of mesoionic-based
molecules and provide guidance for the rational design of molecules with
excellent photoelectric performance in the future.
