Molecular Orbital Calculations of Nonlinear Optical Parameters for Test Molecules of a Highly Amphoteric and Polar Molecule (HAPM)

Abstract

Semiempirical molecular orbital calculations of 2-(4-dicyanomethylenecyclohexa-2,5-dienylidene)-4,5-ethylenedithio-1,3-dithiole and its analogues, as test molecules towards a highly amphoteric and polar molecule (HAPM) designed on the basis of combination of electron-donating and accepting molecular segments with a pseudo-delocalized electron system were carried out to estimate several molecular parameters, in particular, those regarding the second-order optical nonlinearity, in order to examine a difference between the proposed molecular design and the conventional one for the ‚push-pull’ type of molecules. Large values of the first molecular hyperpolarizability are obtained for the present molecules, however, it is turned out that the trade-off relation between hyperpolarizability and transparency of a material is also concerned with these materials. This indicates that the proposed molecular design toward HAPM is unique and can be useful to bring about novel materials with remarkable properties.

Key Words:

• amphoteric molecule
• intramolecular charge transfer
• electronic delocalization
• hyperpolarizability
• second harmonic generation