Second and third-order nonlinear optical properties and molecular parameters of azo chromophores: semiempirical analysis.

The static and frequency dependent average polarizability (<α>), first- and second-hyperpolarizabilities (<β> and <γ>) and highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LUMO) energies of nonlinear optical chromophores with nitro acceptors 1-5 have been investigated by using the Austin Model 1 (AM1), Modified Neglect of Diatomic Overlap (MNDO), MNDO with d orbitals (MNDO-d), Parameterization Method 3 (PM3), Recife Model 1 (RM1) and Parameterization Method 6 (PM6) methods within a time-dependent Hartree-Fock (TDHF) approaches. The electronic properties of chromophores 1-5 have been reported by employing two-state model calculated at Zerner's spectroscopic version of the Intermediate Neglect of Differential Overlap singly excited configuration interaction (ZINDO/S-SCI) method. Also, the molecular hardness (η) and electronegativity (χ) parameters have been obtained by using molecular frontier orbital energies. The <α>, <β>, <γ> HOMO, LUMO energies, η and χ parameters have been investigated with respect to the choice of different semiempirical methods.