Synergistic oxoanion and ligand conformation control of dimensionality in coordination polymers formed via 3,3′-bipyridine tethers: From 1D undulating chains to a doubly interpenetrated 3D framework

Combination of metal perchlorate salts with the organodiimine 3,3′-bipyridine (3,3′-bpy) in aqueous solution has afforded a family of divalent metal coordination polymers with general formulation {[M(H2O)4(3,3′-bpy)](ClO4)2·2 3,3′-bpy} (M = Co, 1; M = Zn, 2; M = Cd, 3). Compounds 1-3 are isomorphous, with single crystal X-ray diffraction revealing 1D [M(H2O)4(3,3′-bpy)]n2n+ undulating polymeric chains formed from the junction of [M(H2O)4]2+ subunits through dipodal syn-conformation 3,3′-bpy. Unligated perchlorate anions and neutral 3,3′-bpy guest molecules, also in a syn conformation, are anchored to the 1D chain motifs through extensive hydrogen bonding patterns. Blue-light luminescence is observed upon ultraviolet excitation of 2 and 3. Use of cobalt nitrate as the metal source resulted in the 3D coordination polymer {[Co(3,3′-bpy)2(H2O)2](NO3)2} (4), which manifests a doubly interpenetrated diamondoid framework constructed from the linkage of Co ions through anti-conformation 3,3′-bpy.