Molecular structure and ring distortions of 1,3-dicyanobenzene in the gas phase and in the crystal

The crystals of 1,3-dicyanobenzene have been obtained by a sublimation meth od. 1,3-Dicyanobenzene crystallizes in the monoclinic system. The X-ray geo metry of the 1,3-dicyanobenzene molecule has been compared with the ab init io (HF/6-31 +G(d) basis sets level) calculated structure in the gas-phase. The difference between equivalent parameters obtained by these methods is a consequence of the intermolecular interactions present in the crystal. The distortion of the benzene ring from the Dbh symmetry is consistent with th e substitution effect caused by two highly polar groups. The distortion of the benzene ring in 1,3-dicyanonbenzene has been compared and discussed in relation to the o- and p-isomers of dicyanobenzene. The differences in the C-C bond lengths of the phenyl ring in the gas-phase have been analyzed in terms of the distribution of the charge density. The calculated charge dens ity and its Laplacian function were analyzed in term of the topological pro perties at the (3,- 1) critical points. Some comments on the crystal packin g and intermolecular interactions present in the crystals of o-, m-and p-di cyanobenzene and their melting points have also been presented. (C) 2000 El sevier Science B.V. All rights reserved.