Vibrational frequencies and electronic structures of 2-amino-1, 9-dihydro-9-[(2-hydroxuethoxy) methyl]-6H-purin-6-one using density functional theory method

In this study, Density Functional Theory (DFT) calculations were conducted on Acyclovir (ACV) hydrate molecular system with the chemical formula of 3[C8H11N5O3]·2[H2O]. Geometry optimization calculations were performed to find the equilibrium structure of 3[C8H11N5O3]·2[H2O]. The optimized geometries were used to find the electronic structures of title molecule, i.e. total energies, frontier molecular orbital energies, atomic charges, and others. The results show that all structural parameters obtained are close to that of experiment. The total energies of 3[C8H11N5O3]·2[H2O] are −70355.92 eV and −70373.84 eV, respectively for DFT/B3LYP/6-31G** and DFT/B3LYP/6-311G** levels of calculations. Using the scheme of Mulliken population analysis (MPA), the highest positive charge was localised on the atom of C12, while for natural atomic charge distribution, C9 atom possesses the highest positive charge. Moreover, the results of vibrational frequencies computed with two different basis sets are close to each other. The computed vibrational frequencies are overall corresponded with the region in the literature studies.