Effect of Anions on the Self-Assembly of Cd(II)-Containing Coordination Polymers Based on a Novel Flexible Tetrakis(imidazole) Ligand

Abstract

Thirteen Cd(II)-containing coordination polymers based on the novel tetradentate ligand tetrakis(imidazol-1-ylmethyl)methane (L), namely, [Cd2(L)2(SO4)2(H2O)2]·4H2O (1), [Cd(L)(H2O)2](NO3)2 (2), [Cd(L)(Br)2]·H2O (3), [Cd(L)0.5(L1)] (4), [Cd5(L2)5(H2O)2]·6H2O (5), [CdL3(L)0.5] (6), [CdL4(L)0.5(H2O)]·H2O (7), [Cd2(L5)2(L)]·2H2O (8), [Cd3(L6)2(L)]·4H2O (9), [Cd3(L7)2(L)(H2O)2]·2.5H2O (10), [Cd(HL8)(L)]·0.75H2O (11), [Cd7(L9)3(μ3-OH)2(L)2]·8H2O (12), [Cd2(L10)(L)(H2O)2]·H2O (13), where H2L1 = fumaric acid, H2L2 = adipic acid, H2L3 = 1,3-benzenedicarboxylic acid, H2L4 = 1,4-benzenedicarboxylic acid, H2L5 = 5-OH-1,3-benzenedicarboxylic acid, H3L6 = 1,3,5-benzenetricarboxylic acid, H3L7 = 1,2,3-benzenetricarboxylic acid, H3L8 = 1,2,4-benzenetricarboxylic acid, H4L9 = 1,2,4,5-benzenetetracarboxylic acid, and H4L10 = 4,4′-oxidiphthalic acid, have been synthesized under hydrothermal conditions. Compound L·5H2O shows a novel three-dimensional (3D) (3,8)-connected supramolecular architecture with a unique (3·52)2(34·42·56·612·73·8) topology. Compounds 1−3 were isolated by the reactions of L with inorganic anions (SO42−, NO3−, Br−). Compound 1 displays a 4-connected PtS network. Compound 2 exhibits a 3D 4-connected zeolite ABW net, while compound 3 is a two-dimensional (2D) (44)-sql net. Compounds 4−8 were isolated by the reactions of L with organic dicarboxylate ligands. 4 exhibits a 2-fold interpenetrating α-Po net, while 5 shows a noninterpenetrating 3D framework. 6 shows a 3D (65·8) CdSO4-type framework, whereas compound 7 has a different 3D framework with (4·62·72·8)(42·62·7·8) topology. 8 shows a 2D layer structure, which is further extended into a 3D supramolecular framework by the hydrogen bonds. Compounds 9−11 have been obtained by the reactions of L with organic tricarboxylate ligands. In 9, the Cd(II) atoms are bridged by L and L6 ligands to form a 3D structure. In 10, the trinuclear Cd(II) clusters are linked by the L and L7 ligands to generate a chiral 3D α-Po structure. In 11, the Cd(II) centers are connected by the L ligands and the partially deprotonated HL8 ligand to yield a 2D layer structure. Compounds 12 and 13 were synthesized by the reactions of L with different organic tetracarboxylate ligands. In compound 12, the L9 ligands link the Cd(II) centers to form a 3D Cd-L9 framework, and the L ligands further stabilize the 3D structure. In compound 13, L10 ligands coordinate to the Cd(II) atoms in tetradentate mode to generate a 2D layer, which is further linked by L ligands to form a 3D framework. The structural differences of compounds 1−13 indicate that the presence of the different anions play an important role in the resulting structures of the coordination polymers. The infrared spectra and luminescent properties were also investigated for the compounds.