Spectroscopic (FT-IR, FT-Raman, NMR) investigation on 2-[(2-amino-6-oxo-6,9-dihydro-3H-purin-9-yl)methoxy]ethyl(2S)-2-amino-3-methylbutanoate by Density Functional Theory

Abstract

Abstract I In the present study, Quantum mechanical approach was carried out on the title compound to study the vibrational spectrum, the stability of the compound, the inter and intra-molecular interactions by using Density Functional Theory (DFT) with B3LYP 6-311++G(d,p) basis set. The B3LYP/DFT method was chosen because diverse studies have shown that the results obtained with it are in good agreement with those determined by other costly computational methods. The computational methods were aided by the experimental spectroscopic techniques, FT-IR, FT-Raman and NMR spectroscopies. The optimized molecular geometry (Fig), the vibrational wavenumbers, the infrared intensities and the Raman scattering activities were calculated. The calculated HOMO and LUMO energies were found to be -6.0856 eV and -2.4833 eV which gives rise to a band gap energy of 3.6023 eV indicating the charge transfer within the molecule. Natural Bond Orbital analysis has been carried out to explain the charge transfer (or) delocalization of charge due to the intra molecular interactions. The total, partial and overlap DOS spectrum were convoluted to study the overlapping interactions of the various bonds present in the compound. Molecular electrostatic potential (MEP) and first order hyperpolarisability calculations were also performed. Mulliken population analysis was made in order to find the charge distribution throughout the compound.