Influence of methyl and nitro group substitutions on the structure and vibrational characteristics of the hydrazo-bridge in 6,6′-dimethyl-3,3′,5,5′-tetranitro-2,2′-hydrazobipyridine

•The crystal structure of 6,6′-dimethyl-3,3′,5,5′-tetranitro-2,2′-hydrazobipyridine was studied.•The IR and Raman spectra of studied compound were recorded.•The IR and Raman wavenumbers were calculated from the optimized geometry of molecule.•X-Ray, IR, Raman and DFT methods confirm the existence of an intramolecular HBs.•The vibrational characteristics of the hydrazo-bond were reported.

The crystal and molecular structures of 6,6′-dimethyl-3,3′,5,5′-tetranitro-2,2′-hydrazobipyridine have been determined by X-ray diffraction and DFT quantum chemical methods. The B3LYP/6-311G(2d,2p) approach has been used in the theoretical calculations. The studied compound crystallizes in the monoclinic P21/n space group (Z = 2) with one-half molecule in the asymmetric unit. In the molecular structure of the studied compound the intramolecular NH⋯O hydrogen bonds play a crucial role. These molecules also interact in the unit cell by means of weak intermolecular CH⋯O contacts. IR and Raman spectra have been measured and simulated from the optimized geometry. In the calculations the monomeric unit has been taken into account because the intermolecular interactions between the components of the unit cell are weak and the factor group splitting is not observed in the experimental spectra. The structural and vibrational properties of the hydrazo bonds have been described with their relation to the intramolecular NH⋯O interaction existing in the structure of the monomeric form.