STRUCTURE, POLARIZED MICRO-RAMAN AND FT-IR SPECTRA, AND AB-INITIO CALCULATIONS OF 1,2-DICYANOBENZENE

The infrared and polarized Raman spectra of solid 1,2-dicyanobenzene ( phthalonitrile) have been recorded and measured. A general assignment of the vibrational fundamentals has been proposed on the basis of the intensity changes observed in the polarized spectra. A powder X-ray di ffraction study has been performed showing that this compound crystall izes in the orthorhombic space group, Pmmn, with lattice parameters of a = 12.625(4) angstrom, b = 6.974(3) angstrom, c = 3.909(2) angstrom, and Z = 2. Ab initio quadratic force field calculations at the 3-21G and 6-31G levels were carried out. The frequencies, normal modes, and infrared intensities obtained from scaled quantum mechanical force fie lds support the previous results from experimental data.