Helical zinc complexes of pyrazine-pyridine hybrids

The zinc(II) complexes 1aZnCl(2) and 1bZnCl(2) (1a: 2-(6,2"-bipyrid-2'-yl)-3-(2-pyridyl)pyrazine; 1b: 2-(6',2'-bipyrid-2'-yl)-5,6-dinitrilo-3-(2-pyridyl)pyrazine) were prepared by treatment of the ligands with ZnCl2. The structures of both were investigated by Xray crystallography and H-1 NMR spectroscopy. Both complexes display proton deshielding phenomena that are attributed to a twisted solution-state molecular conformation. In the solid state, 1aZnCl(2) exhibits a high degree of torsion about the axis through the uncomplexed pyridine ring and the pendant chlorine atoms. The solid-state structure and solution-state self-associative behavior of 1bZnCl(2) are indicative of a partial self-assembly motif.