Vibrational spectra, crystal structure, DFT quantum chemical calculations and conformation of the hydrazo - bond in 6-methyl-3-nitro-2-(2-phenylhydrazinyl)pyridine

The crystal and molecular structures of 6-methyl-3-nitro-2-(2-phenylhydrazinyl)pyridine (6-methyl-3-nitro-2-phenylhydrazopyridine) have been determined by X-ray diffraction and quantum chemical DFT analysis. The crystal is monoclinic, space group C2/c, with Z = 8 formula units in the elementary unit cell of dimensions a = 16.791(4), b = 6.635(2), c = 21.704(7) angstrom, beta = 100.54(3)degrees. The molecule consists of two nearly planar pyridine subunits. A conformation of the linking hydrazo-bridge C-NH-NH-C is bend and the dihedral angle between the planes of the phenyl and pyridine rings is 88.2(5)degrees. The hydrogen bonding of the type N-H center dot center dot center dot N and possibly also C-H center dot center dot center dot O favors a dimer formation in the crystal structure. The dimers are further linked by a N-H center dot center dot center dot O hydrogen bond, so forming a layer parallel to the ab plane. The molecular structure of the studied compound has been determined using the DFT B3LYP/6-311G(2d,2p) approach and compared to that derived from X-ray studies. The IR and Raman wavenumbers have been calculated for the optimized geometry of a possible monomer structural model but the possibility of the dimer formation through the N-H center dot center dot center dot N hydrogen bond has also been considered. The structural and vibrational properties of the intra-molecular N-H center dot center dot center dot O interaction are described. (c) 2013 Elsevier B.V. All rights reserved.