Prediction of electronic structure, dielectric and thermodynamical properties of flurbiprofen by density functional theory calculation

Abstract

The molecular structure of the pain killer drug Flurbiprofen has been fully optimized using Berny's optimization algorithm in Gaussian 09, using redundant internal coordinates. The dipole moments, polarizability tensors, average polarizability, anisotropy, first molecular hyperpolarizability, thermodynamics properties, dielectric constant, refractive index, dielectric susceptibility, molar refractivity, IR and Raman spectra have also been studied. A tentative assignment of the IR vibration frequencies was equally carried out. This was done by using Density functional theory calculations with three different functional B3LYB, X3LYP and BPBE by employing cc-pVDZ basis set. The calculated energy band gap (Egap) of the molecule obtained by using HOMO and LUMO molecular orbitals show that the molecule has an Egap value of 0.195 eV, 0.201 eV and 0.244 eV at the BPBE, B3LYP and X3LYP levels respectively. The first molecular hyperpolarizability value obtained by using the BPBE (6.79187 × 10−30 esu), B3LYP (5.07308 × 10−30 esu) and (2.74471 × 10−30 esu) methods are very large compared to that of Urea (0.1947 × 10−30 esu) reported in literature. The results also show that the molecule has a dielectric constant of 2.85 × 10−11, 3.03 × 10−11 and 2.99 × 10−11 obtained at the PBPE, B3LYP and X3LYP levels respectively. Equally, our IR and Raman spectra were in the same range as those reported in literature.