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′- bipyridmium dichloride (H₂BpybcCl₂) as a versatile ligand, has been designed and synthesized by nucleophilic substitution reaction. A series of transitional metal coordination polymers of {(Bpybc) ₃[M₂(H₂O)₆](OH)₄· 15H₂O}_n (M = Mn 1, Ni 2, Co 3) were synthesized by addition of MCl₂ into aqueous solution of H₂BpybcCl ₂. X-ray single crystal diffraction studies confirm that the complexes are isostructural to each other and crystallize in space group R3 (no. 148) with a = b = 17.525(3) Å, c = 26.230(5) Å, 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.