Cadmium(ii) and zinc(ii) complexes with rigid 1-(1H-imidazol-4-yl)-3-(4H-tetrazol-5-yl)benzene and varied carboxylate ligands

Abstract

Six new coordination polymers [Cd₂(HL)₂(pbda)(H₂O)₂]·4H₂O (1), [Cd₂(HL)₂(mbda)(H₂O)₂]·6H₂O (2), [Cd(H₂L)(mmbda)(H₂O)] (3), [Cd₂(H₂L)₂(btca) (H₂O)₂]·4H₂O (4), [Zn₂(H₂L)₂(btca)] (5) and [Zn₆(H₂L)₆(btca)₃] (6) were synthesized by reactions of cadmium(II)/zinc(II) salts with a rigid ligand 1-(1H-imidazol-4-yl)-3-(4H-tetrazol-5-yl)benzene (H₂L) and different carboxylic acids of 1,4-benzenedicarboxylic acid (H₂pbda), 1,3-benzenedicarboxylic acid (H₂mbda), 5-methyl-1,3-benzenedicarboxylic acid (H₂mmbda), 1,2,4,5-benzenetetracarboxylic acid (H₄btca), respectively. The structures of the complexes were determined by single crystal X-ray diffraction analysis. Although complexes 1 and 2 possess the same two-dimensional (2D) network with (4·8²)-fes topology built from Cd(II)–(HL)⁻ moieties, different coordinated orientation of auxiliary carboxylates of pbda²⁻ and mbda²⁻ pillar the 2D layer into distinct frameworks. Complex 1 is an unusual binodal (3,4)-connected three-dimensional (3D) dmc net with Point (Schläfli) symbol of (4·8²)(4·8⁵) while 2 is a rare binodal (3,4)-connected 3D architecture with a (4·6·8)(4·6²·8³) fsc-3,4-C2/c topology. Complexes 3 and 4 have the same 2D networks with (4,4) topology, and H-bonding or π–π stacking interactions extending the 2D layers into 3D supramolecular frameworks, respectively. Complexes 5 and 6 present a pair of pseudopolymorphs, and 5 is an uninodal (4,4)-connected 3D net with Point (Schläfli) symbol of (6²·8⁴)(6⁴·8²)₂ while 6 is an unprecedented penta-nodal 4-connected net with (4·6²·8³)₂(4·6⁴·8)₂(6²·8⁴)(6⁴·8²)₄ topology. The thermal stability and photoluminescent property of the complexes were investigated.