Nonlinear optical (NLO) properties of the octupolar molecule: Structure-function relationships and solvent effects

Nonlinear optical (NLO) properties of two series of octupolar molecules are investigated to establish the structure-NLO-property relationships by carrying out the ab initio (HF/6-31G) calculations of the molecular polarizability (a), the first hyperpolarizability (β), and the second hyperpolarizability (γ). It is found that, as the charge-transfer character of the ground state increases by introducing a stronger donor, (i) the absolute BLA value decreases and (ii) α, β, and γ increase. Thus, the design strategy to maximize the NLO properties of the octupolar molecule is established. Also, the solvation-induced effects on the NLO properties are studied by using the self-consistent reaction field (SCRF) method. As the solvent polarity increases, α, β, and γ increase monotonically. These observations are in good agreement with the predictions based on the valence-bond three-charge-transfer model.