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

Two novel three-dimensional metal-coordination polymers [Cd<sub>2</sub>(<b>L</b>)<sub>4</sub>(μ<sub>2</sub>-X)(X)(H<sub>2</sub>O)]<sub><i>n</i></sub> [X = Cl (<b>1</b>) and Br (<b>2</b>)] have been solvothermally synthesized by the self-assembly of an unsymmetric bridging ligand, [<b>L</b> = 2-(1<i>H</i>-imidazol-1-ylmethyl)-1<i>H</i>-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.