Modified bipyridines: 5,5 '-diamino-2,2 '-bipyridine metal complexes assembled into multidimensional networks via hydrogen bonding and pi-pi stackinginteractions

A new synthetic route for the synthesis of 5,5'-diamino-2,2-bipyridine (5) based on the coupling of 2-chloro-5-aminopyridine in the presence of NiCl2 x 6 H2O/PPh3/Zn in dimethylformamide is described. The reactions of the pot entially ambidentate ligand 5 with salts of the transition metals Mn, Fe, N i, Cu, Zn, Ag, and Cd gave a variety of 13 metal-ligand complexes depending on the anion, the crystallization conditions and the metal-to-ligand ratio . The complexes obtained were characterized by thermal analyses, NMR includ ing Cd-113-NMR, IR, and for the iron complex Fe-57-Mossbauer spectroscopy. The structure of eight of the compounds was elucidated by X-ray crystallogr aphy. All of these metal complexes show a bipyridine-metal coordination. Th e amino functionality was never involved in metal coordination. The intermo lecular arrangement is dictated by hydrogen bonding from the amino function ality and by pi-pi stacking of the bipyridine rings.