Crystal structure, vibrational and DFT simulation studies of melaminium dihydrogen phosphite monohydrate

• XRD, FTIR, FT-Raman and DFT studies of melaminium dihydrogenphosphite monohydrate were done.
• It crystallizes in monoclinic crystal system and the space group is P21/c.
• The melaminium cation is joined with dihydrogen phosphite anion and water molecule.
• The electrostatic potential of the molecule is +1.94e × 10−2 to −1.94e × 10−2.

The crystal structure investigations of melamine with phosphorous acid, namely melaminium dihydrogenphosphite monohydrate (C3N6H7·H2PO3·H2O) have been investigated by means of single crystal X-ray diffraction method. The title compound crystallizes in monoclinic crystal system, and the space group is P21/c with a = 10.069 Å, b = 21.592 Å, c = 12.409 Å and Z = 12. The vibrational assignments and analysis of melaminium dihydrogen phosphite monohydrate have also been performed by FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical simulations were performed with DFT (B3LYP) method using 6-31G**, cc-pVTZ, and 6-311++G** basis sets to determine the energy, structural, thermodynamic parameters and vibrational frequencies of melaminium dihydrogen phosphite monohydrate. The hydrogen atom from phosphorous acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak OH···O and NH···O hydrogen bonds shows notable vibrational effects.