Solid-State Intermolecular Contacts Involving the Nitrile Group in p-Cyano-N-(p-cyanobenzylidene)aniline and 4,4′-(azinodimethylidyne)bis-benzonitrile

As part of an investigation of the solid-state intermolecular contacts in which the nitrile group participates, the crystal structures of p-cyano-N-(p-cyanobenzylideneani- line), C15H9N3 (CN/CN) and 4,4 0 -(azinodimethylidyne) bis-benzonitrile, C16H10N4 (CN//CN) have been determined at -100 C. Cell parameters for CN/CN: a = 4.7270(9) A ˚ , b = 10.443(2) A ˚ ,c = 11.943(2) A ˚ ; a = 90, b = 98.70(3), c = 90; monoclinic, space group P21/c. Cell parameters for CN//CN: a = 3.8008(8) A ˚ ,b = 7.9627(16) A ˚ ,c = 11.181(2) A ˚ ; a = 70.23(3), b = 84.66(3), c = 81.93(3); triclinic, space group P1. Both molecules occupy crystal- lographic inversion centers, which requires that (CN/CN) be disordered. Both molecules assume nearly planar con- formations in the solid state. Neither (CN/CN) nor (CN// CN) is isostructural with its halogen-nitrile substituted analogues, although (CN/CN) is found to be isostructural with the corresponding stilbene. Both (CN/CN) and (CN// CN) engage in centrosymmetric H-bonding interactions that define an R2 (10) motif. This motif is also observed in many related structures, although noteworthy exceptions can be found.