Molecular polarizability and first hyperpolarizability of octupolar molecules: Donor-substituted triphenylmethane dyes

Molecular polarizabilities and hyperpolarizabilities of a series of octupolar molecules that are donor-substituted triphenylmethane dyes are calculated. The four-state model of an octupolar molecule is used to describe the nonlinear optical properties of this type of molecules. As the charge-transfer character of the ground state is increased by using a strong donor, both the molecular polarizability and first hyperpolarizability increase monotonically. These patterns are in strong contrast with those exhibited by the linear push-pull polyene. On the basis of these results, it is suggested that a common strategy to maximize the molecular polarizability can also be used to optimize the first hyperpolarizability in the case of octupolar molecules such as triphenylmethane dyes.