Synthesis, Structures, and Properties of Zinc(II) and Cadmium(II) Complexes with 1,2,4,5-Tetrakis(imidazol-1-ylmethyl)benzene and Multicarboxylate Ligands

Five new coordination polymers, namely, [Cd(L)0.5(HBTC)]·0.2H2O (1), [Cd3(L)2(BTA)2(H2O)2]·H2O (2), [Cd2(L)0.5(BTEC)]·H2O (3), [Zn3(L)(BTC)2(H2O)2]·3H2O (4), and [Zn2(μ2-OH)(L)0.5(BTA)]·H2O (5) were synthesized under hydrothermal conditions by reactions of corresponding Cd(II) or Zn(II) salts with the mixed multidentate ligands of 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene (L) and 1,3,5-benzenetricarboxylic acid (H3BTC), 1,3,5-benzenetriacetic acid (H3BTA), 1,2,4,5-benzenetetracarboxylic acid (H4BTEC), respectively. The complexes were characterized by single crystal X-ray diffraction, IR, and thermogravimetric and elemental analyses. The Cd(II) complex 1 is a two-dimensional (2D) network with infinite one-dimensional (1D) Cd-HBTC2− chains linked together by L ligands, while the Zn(II) complex 4 with the same mixed ligands has a three-dimensional (3D) structure. The Cd(II) complex with BTA3− and L ligands (2) features an unusual 3D framework, and the Zn(II) complex 5 shows a 3D structure with (63)2(42,84)(4,63,86)2 topology. Complex 3 possesses a 3D structure consisting of a Cd-BTEC4− framework and Cd2O2-L 1D chain. The results showed that the coordination geometry of metal centers and the conformation and coordination mode of organic ligands play an important role in determining the structure and topology of the complexes. The luminescence properties of 1−5 were studied in the solid state at room temperature.