FT-IR, FT-Raman, and DFT computational studies of melaminium nitrate molecular–ionic crystal

The experimental and theoretical vibrational spectra of melaminium nitrate were studied. The Raman and infrared (FT-IR) spectra of the melaminium nitrate and its deuterated analogue were recorded in the solid phase. Molecular geometry and vibrational frequency values of melaminium nitrate in the electronic ground state were calculated using the density functional method (B3LYP) with the 6-31++G(d,p) basis set. The calculated results show that the optimized geometry can well reproduce the crystal structure, and the theoretical vibrational frequency values show good agreement with experimental values. The NBO analysis reveals that the N–H···O and N–H···N intermolecular interactions significantly influence crystal packing in this molecule.

► Solid state vibrational spectra of melaminium nitrate and deuterated analogue were recorded.
► B3LYP method in conjunction with the 6-31++G(d,p) basis set was used to compute FTIR and FTRaman spectra.
► Octupolar melamine participates in spontaneous supramolecular self-organization phenomenon.
► The value of the energy separation between the HOMOs and LUMOs is very large.
► NBO analysis indicates intermolecular interactions influencing crystal packing.