An experimental and theoretical study on concomitant polymorphism of a dithiocarbonimidates derivate in a single space group

The title organic dithiocarbonimidates derivate crystallizes in two different polymorphic modifications. The conformational differences between the two crystalline modifications lead to differences in crystal packing and thus result in the formation of the two polymorphic forms. In this paper, we will report a combined experimental and theoretical investigation of the molecular structure and spectroscopic parameters (FT-IR, 1H NMR and 13C NMR) of 5-benzoyl-2-oxo-4-phenyl-1(2H)-[diethyldithiocarbonimidate]-pyrimidine.The molecular geometry was also optimized using density functional theory (DFT/B3LYP) method with the 6-311G(d,p) basis set in ground state and compared with the experimental data. From the optimized geometry of the molecule, vibrational frequencies, Gauge-Independent Atomic Orbital (GIAO) 1H and 13C-NMR chemical shift values, molecular electrostatic potential (MEP) distribution, frontier molecular orbitals (FMO) and thermodynamic properties of the title compound were performed at B3LYP/6-311G(d,p). The calculated MEP map verifies the solid-state interactions. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. The results of the calculations were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. The calculated HOMO–LUMO energy gap shows that charge transfer occur within the molecule. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential (ESP).