Syntheses and structures of two noncentro symmetric inorganic–organic composite materials based on metal sulfate and 4,4′-bipyridine (M = Ni, Fe)

Two new noncentro symmetric inorganic–organic composite materials have been obtained by reactions of metal (Ni or Fe) sulfate salts and 4,4′-bpy (bpy = bipyridine). X-ray single-crystal diffraction analyses reveal that in compound 1, sulfate dianions show three kinds of coordination modes and act not only as ligands bound to metal sites but also as charge-compensating and space-filling species. The void of the cavities in 1 is estimated to be about 13.5% by PLATON calculation when the lattice waters are removed. The structure of compound 2 exhibits one-dimensional infinite chains in which the –Fe–bpy– chain subunits are interconnected by hydrogen-bonding interactions and π–π stacking interactions.