Ab initio and DFT study of the static dipole (hyper)polarizabilities of benzaldehyde and thio-benzaldehyde molecules in gas phase

Abstract

The results of ab initio and density functional theory DFT calculations of dipole moments and electronic contributions to static dipole (hyper)polarizabilities of benzaldehyde and thiobenzaldehyde molecules in gas phase are presented. These properties were evaluated at the SCF, MP2, MP4 and DFT (B3LYP) levels of theory with a selection of basis sets that include polarization and diffuse functions on the C, O, S and H atoms: 6-31+G(d,p) (A), 6-311++G(3d,3p) (B), 6-31+G(d*,p) (C) and the Sadlej (D) basis sets, using HF/A, MP2/A and B3LYP/A optimized geometries under the Cs symmetry restriction. The C basis set has been optimized in terms of the maxima second hyperpolarizability at HF level. Both MP2 and MP4 methods, performed at full electron configuration, have shown to perform well in the calculation of such properties. Considering the basis sets effects, the impact of the electron correlation in the (hyper)polarizabilities of these molecules is analyzed systematically in terms of the differences between MP2 and MP4 perturbation theory and those from DFT(B3LYP) methods. The effects of substitution of the C=S fragment by the C=O group in the benzaldehyde molecule, giving the formation of thiobenzaldehyde, lead to enhanced results of nonlinear optical properties in terms of their first (β) and second hyperpolarizability (γ), that shown to be higher than those for para-Nitroaniline molecules. In fact, thiobenzaldehyde exhibit significant values of nonlinear optical properties which make this chromophore a prospective building block for nonlinear optical materials.