Natural bond orbital analysis and vibrational spectroscopic studies of H-bonded N,N′-diphenylguanidinium nitrate

NIR-FT Raman and FT-IR spectra of the crystallized biologically active molecule N,N′-diphenylguanidinium nitrate (DGN) have been recorded and analyzed using quantum chemical computations based on density functional theory. The extraordinary basicity and strong stability of this novel bioactive compound has been discussed as the consequence of resonance stabilization leading to Y-aromaticity and hydrogen bonding. This peculiar Y-delocalization character of DGN is well reflected in the optimized geometry and bond order (BO) calculations. The observance of the equality of C–N bond lengths in the protonated species indicates delocalization of the π-electron system. The spectroscopic and natural bonds orbital (NBO) analysis confirms the occurrence of strong network of inter molecular hydrogen bonds. The changes in electron density in the global minimum and in the energy of hyperconjugative interactions of DGN calculated by second order perturbation theory have been studied extensively in comparison with the values of the neutral species. The observed characteristic ring vibrations are well fit with the theoretical values calculated at B3LYP/6-31G∗ level.