Syntheses, Structures and Third-Order Nonlinear Optical Properties of Two-Dimensional Rhombohedral Grid Coordination Polymers: [Cd(imz)3]2(BTC)·0.5H2O and [Cu4(H2O)2(imz)8](BTC)2·7H2O(BTC = 1, 2, 4, 5-benzenetetracarboxylate anion, imz = imidazole)

Abstract

Hydrothermal reactions of 1, 2, 4, 5-benzenetetracarboxylic acid (H4BTC) with cadmium acetate and copper acetate in the presence of imidazole (imz) resulted in two new coordination polymers, namely, [Cd(imz)3]2(BTC)·0.5H2O 1, [Cu4(H2O)2(imz)8](BTC)2·7H2O 2. Two compounds have been characterized structurally using single-crystal diffraction, elemental analysis, and FT-IR spectrum. In compound 1, the hexa-coordinated Cd(II) ions are bridged by BTC to form two-dimensional rhombohedral grid sheets. In compound 2, the coordination polyhedrons [CuO4N2] and [CuO3N2] are bridged by BTC to lead to a 2D framework with rectangular-shaped cavities. Two compounds of third-order nonlinear optical (NLO) properties were determined by Z-scan technique in DMSO solution. The results showed that two compounds exhibited strong NLO absorption and strong self-focusing effects. The third-order NLO absorptive coefficients β(MKS) are 5.45 × 10−11 m W−1 for 1 and 9.81 × 10−11 m W−1 for 2. The refractive indexes γ(MKS) are 3.96 × 10−18 m2 W−1 for 1 and 7.60 × 10−18 m2 W−1 for 2. The third-order NLO susceptibility χ(3) are calculated to be 1.25 × 10−11 for 1, 2.32 × 10−11 esu for 2, respectively. These values are larger than those of metal coordination polymers reported. Two novel two-dimensional transition metal coordination polymers have been reported. Two compounds exhibit strong NLO absorption and strong self-focusing effects. The third-order NLO susceptibility χ(3) are calculated to be 1.25 × 10−11 for 1, 2.32 × 10−11 esu for 2, respectively