Two New Nonlinear Optical and Ferroelectric Three-Dimensional Metal−Organic Frameworks with an sqp-net

Two novel three-dimensional metal-coordination polymers [Cd₂(L)₄(μ₂-X)(X)(H₂O)]_n [X = Cl (1) and Br (2)] have been solvothermally synthesized by the self-assembly of an unsymmetric bridging ligand, [L = 2-(1H-imidazol-1-ylmethyl)-1H-benzoimidazole], and cadmium salts with different anions, respectively. The two complexes are isostructural and exhibit an acentric sqp-net, in which the cadmium ions act as unusual five-connected nodes. The induction of the flexible and unsymmetric ligand leads them to crystallize in a noncentrosymmetric polar packing arrangement, which displays a second harmonic generation response and ferroelectric behaviors.