Quantum chemical calculations on the geometrical, conformational, spectroscopic (FTIR, FT-Raman) analysis and NLO activity of milrinone (5-cyano-2-methyl-(3,4'-bipyridin)-6(1h)-one) by using Hartree-Fock and density functional methods

The Fourier transform infrared (FTIR) and Fourier transform Raman (FT-Raman) spectra of milrinone (5-Cyano-2- methyl-(3,4'-bipyridin)-6(1H)-one) in solid phase have been recorded and analyzed. Quantum chemical calculations of the optimized molecular structure, energies, molecular surfaces, conformational, nonlinear optical (NLO) properties and vibrational studies of milrinone have been calculated by using Hartree-Fock (HF) and density functional theory (DFT/B3LYP) with 6-31G(d,p) basis set. Obtained results on the geometric structure are compared with the experimental X-ray diffraction. The calculated highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies also confirm that charge transfer occurs within the molecule. Molecular parameters like global hardness (η), global softness (σ) and electronegativity (χ) have been calculated with the results obtained from the HOMO and LUMO molecular orbital energies. Nonlinear optical parameters (mean polarizability (<α>), the anisotropy of the polarizability (<Δα>) and the mean first-order hyperpolarizability (<β>)) of the title compound have been investigated theoretically. A detailed interpretation of the infrared and raman spectra of milrinone have been performed with HF and DFT calculations and the potential energy distribution (PED) obtained from the vibrational energy distribution analysis (VEDA4) program. (author)