Two-dimensional noninterpenetrating transition metal coordination polymers with large honeycomb-like hexagonal cavities constructed from a carboxybenzyl viologen ligand

A viologen derivative, 1, 1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride (H(2)BpybcCl(2)) as a versatile ligand, has been designed and synthesized by nucleophilic substitution reaction. A series of transitional metal coordination polymers of {(Bpybc)(3)[M-2(H2O)(6)](OH)(4)center dot 15H(2)O}(n) (M = Mn 1, Ni 2, Co 3) were synthesized by addition of MCl2 into aqueous solution of H(2)BpybcCl(2). X-ray single crystal diffraction studies confirm that the complexes are isostructural to each other and crystallize in space group R (3) over bar (no. 148) with a = b = 17.525(3) angstrom, c = 26.230(5) angstrom, and Z = 3 for exemplified Mn complex. Each metal ion coordinates to three Bpybc ligands, and each Bpybc ligand bridges two metal ions, thereby creating an infinite two-dimensional (6, 3) network with large honeycomb-like hexagonal cavities. The whole structure is a noninterpenetrating framework sustained by hydrogen bonding interactions.