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 (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 H2BpybcCl2. X-ray single crystal diffraction studies confirm that the complexes are
isostructural to each other and crystallize in space group R3̄ (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.