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 (H 2 O) 6 ](OH) 4 ·15H 2 O} n (M = Mn 1, Ni 2, Co 3 ) were synthesized by addition of MCl 2 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 3̄ (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.