Density functional theory and Ab initio studies of vibrational spectroscopic (FT-IR, FT-Raman and UV) first order hyperpolarizabilities, NBO, HOMO–LUMO and TD-DFT analysis of the 1,2-Dihydropyrazolo (4,3-E) Pyrimidin-4-one

Fourier transform Raman and Fourier transform infrared spectra of 1,2-Dihydropyrazolo (4,3-E) Pyrimidin-4-one were recorded in the regions 3500–100 cm−1 and 4000–400 cm−1 respectively in the solid phase. 1,2-Dihydropyrazolo (4, 3-E) Pyrimidin-4-one is used to treat hyperuricemia and its complication including chronic gout. The equilibrium geometry harmonic vibrational frequencies, infrared intensities and Raman intensities were calculated by Hartee Fock and density functional B3LYP methods with 6-31G (d, p) basis set, using Gaussian 03W program package on a Pentium IV/1.6 GHz personal computer. The thermodynamic functions of the title compound were also performed at the above methods and basis set. A detailed interpretation of the infrared and Raman spectra of 1,2-Dihydropyrazolo (4,3-E) Pyrimidin-4-one is reported. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV–vis of the compound was recorded. The calculated HOMO and LUMO energies show that chemical activity of the molecule. The first order hyperpolarizability (β) of this novel molecular system and related properties of 1,2-Dihydropyrazolo (4,3-E) Pyrimidin-4-one are calculated using HF/6-31G (d, p) method on the finite field approach. The experimental spectra also coincide satisfactorily with those of theoretically constructed spectra.

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► 1, 2,-Dihydropyrazolo (4, 3,-e) Pyrimidin – 4 – one is used for the treatment of hyperuricemia.
► MEP confirms the non-existence of intermolecular interactions within the molecule.
► Frontier molecular orbital plays an important role in the electric and optical properties.