Vibrational study, crystal structure and quantum calculations of 2,2 '-azobipyridine and 4,4 '-dimethyl-3,3 '-dinitro-2,2 '-azobipyridine

摘要

Synthesis of 2,2'-azobipyridine and 4,4-dimethyl-3,3'-dinitro-2,2'-azobipyridine is described. The X-ray structure of the later compound is reported and discussed in terms of its molecular structure with a particular attention to the conformation of the azo-bond and intermolecular C-(HO)-O-... bonds. The crystal is monoclinic, space group P2(1)/c, with the unit cell parameters a = 12.388(2), b = 14.983(3), c = 7.370(1) Angstrom, and beta = 102.49(3)degrees. The asymmetric unit consists of two 3-nitro-4-methyl-pyridine units linked by the -N=N- diazene bond. The pyridine rings are planar. The methyl carbon and the N atom of the nitro groups, substituted to the ring, are lying approximately in the plane. In the crystal structure the molecules are arranged in dimers due to the hydrogen bonding between the methyl group and the oxygen of the nitro group of the molecule related by a centre of symmetry. Fourier transform IR and Raman spectra of this compound have been measured and compared to the spectra of 2,2'-azobipyridine. The 6-31G basis set with the B3LYP and MPW1PW31 functionals have been used to discuss the structure and dynamics of the compounds studied. (C) 2004 Elsevier B.V. All rights reserved.