Supramolecular interaction patterns in the zinc(II) dichloride and tin(IV) tetrachloride complexes with dipyrido[f,h]quinoxaline-6,7-dicarbonitrile.

This study characterizes the supramolecular synthons that dominate the intermolecular organization of the title compounds, namely dichloridobis(dipyrido[f,h]quinoxaline-6,7-dicarbonitrile)zinc(II), [ZnCl(2)(C(16)H(6)N(6))(2)], (I), and tetrachlorido(dipyrido[f,h]quinoxaline-6,7-dicarbonitrile)tin(IV), [SnCl(4)(C(16)H(6)N(6))], (II), in their respective crystal structures. Molecules of (I) are located on 2(b) axes of rotational symmetry. Their crystal packing is stabilized mostly by pi-pi stacking and dipole-dipole attractions between the organic ligand fragments of inversion-related neighbouring species, as well as by weak intermolecular C-H...N hydrogen bonds. On the other hand, Cl...pi and N...pi interactions seem to direct the crystal packing in (II), which is unusual in the sense that its aromatic fragments are not involved in pi-pi stacking. Molecules of (II) are located on m(b) planes of mirror symmetry. This study confirms the diverse structural chemistry of this organic ligand, which can be involved in a wide range of supramolecular interactions. These include effective coordination to various metal ions via the phenathroline N-atom sites, pi-pi stacking and pi...halogen contacts through its extended pi-system, and hydrogen bonding and N...pi interactions through its nitrile groups. The competing natures of the latter make it difficult to predict a priori the preferred supramolecular motif that may form in a given structure.