Theoretical Investigations on One-Photon Absorption Wavelengths and First Hyperpolarizabilities of Dipolar Subunits Described for an Octupolar System

The microscopic second-order nonlinear optical (NLO) phenomena of dipolar subunits described for an octupolar system have been investigated by means of calculating both dispersion-free and also frequency-dependent first hyperpolarizability (beta) values from the density functional theory (DFT) and time-dependent Hartree-Fock (TDHF) approaches, respectively. We have estimated the maximum one-photon absorption (OPA) wavelengths by quantum chemical computations utilizing a configuration interaction (CI) technique for the title molecules in the UV area to be lower than 450 nm, indicating well optical transparencies to the visible beam. To find out the optical nonlinearity behaviour describing the molecular orbital structures; the highest occupied molecular orbitals (HOMOs), the lowest unoccupied molecular orbitals (LUMOs) and the HOMO-LUMO energy band gap properties belonging to the first and second frontier MOs have been computationally produced by the DFT procedure.