Molecular structure and spectroscopic characterization of Metformin with experimental techniques and DFT quantum chemical calculations

Metformin is one of the important antidiabetic drugs to treat non – insulin dependent diabetes mellitus. A complete vibrational assignment and analysis of the fundamental modes of Metformin was carried out using FT-IR, FT-Raman and Quantum Chemical studies. The observed vibrational data were compared with the wave numbers derived theoretically. Thermodynamic properties like entropy, heat capacity and enthalpy have been calculated for the molecule. HOMO, LUMO energy gap has been calculated, the intra-molecular contacts have been interpreted using natural bond orbital (NBO) and Natural Localized Molecular Orbital (NLMO) analysis. Finally the Mulliken Population Analysis on atomic charges of the title compound has been calculated. The B3LYP/6-311++G (d, p) based NMR calculation procedure was also done. The NLO properties of the molecule have also been studied. It was used to assign the 13C and 1 H NMR chemical shift of Metformin. The results of the calculations were applied to simulated spectra of the title compound which show excellent agreement with observed spectra.