Ab initio and DFT study of the dipole (hyper) polarizabilities of p-nitrophenylphosphine molecule

Abstract

The static dipole (hyper) polarizabilities (α,β and γ) of p-nitrophenylphospine (PNPhP), a hypothetical Push-Pull organic molecule, were calculated using ab initio (HF, MP2, MP4) and density functional theory DFT (B3LYP, CAM-B3LYP, WB97X-D) hybrid approaches, in conjunction with the standard 6-31+G(d,p) and 6-311++G(3d,3p) basis sets. Similar (hyper) polarizability calculations were additionally carried out for p-Nitroaniline PNA molecule for comparison purposes. These response properties were evaluated within the Finite Field methodology based in the Kurtz equations, where the effects of replacing the -NH₂ donor group of PNA by the -PH₂ group originating the p-nitrophenylphospine PNPhP molecule are analyzed. The results of α, β and γ properties evaluated at different levels of theory show that PNPhP molecule is much more (hyper)polarizable than PNA one. Electron correlation effects, evaluated at MP2, MP4, DFT/B3LYP, CAM-B3LYP and WB97X-D levels of theory, show that α_ave increases between 7 to 16% with respect to the HF values. Likewise, the largest responses are obtained with the most extended basis sets such as 6-311++G(3d,3p), where polarizability increase between 4 to 9% with respect to 6-31+G(d,p) one. The tendencies for β and γ NLO values follow the electron density delocalization of the molecular system, that is more extended in PNPhP than PNA one. Electron correlation effects increase β and γ properties in the order of two or three times with respect to the HF values. Finally, the impact of dynamic and solvent effects on the first hyperpolarizability of PNA molecule were also taken into account, which are discussed in terms of recent literature. The analysis of results, allow us to conclude that PNPhP is an interesting hypothetic molecule that can be useful as building block for the design and creation of new materials with enhanced nonlinear optic applications.