Six new metal–organic frameworks (MOFs), namely, [Pb­(H2IDC)2(H2O)] n (1), {[Pb­(H2IEDC)2)]·3H2O} n (2), [Ca2(HIDC)2(H2O)] n (3), {[Ca2(IEDC)2(H2O)2]·H2O} n (4), {[Cd­(HIDC)­(H2O)] n (5), and {[Cd2(HIEDC)2·3H2O} n (6) (H3IDC = 4,5-imidazoledicarboxylic acid, H3IEDC = 2-ethyl-1H-imidazole-4,5-dicarboxylic acid) were hydrothermally synthesized and characterized. Single-crystal X-ray diffraction shows the ligand H3IDC is partially deprotonated with H2IDC– and HIDC2– forms in three corresponding compounds 1, 3, and 5, meanwhile ligand H3IEDC also presents different deportonated motifs of H2IEDC–, IEDC3–, and HIEDC2– in 2, 4, and 6, respectively. Moreover, these partially or fully deportonated ligands coordinate in the μ1 to μ5 manner to generate one-dimensional (1D) → three-dimensional (3D) coordination polymers, displaying 10 different coordination modes. Both 1 and 2 have 3D supramolecular networks assembled via hydrogen bonding interactions but different in structure topologies. Complex 1 is a 1D coordination chain and 2 has a two-dimensional (2D) wave layer-like structure with 44 topology. Complex 3 is a 3D MOF with 310·425·510 topology built up from linear 2-connected HIDC2– as a linker and 10-connected tetranuclear metal unit [Ca4(μ2-O)6] as a node. However, complex 4 presents a 2D MOF with 36·46·53 topology. Different from 3 and 4, with the 4-connected binuclear metal unit [Cd­(O–C–O)]2 as a node, a wave-like 2D MOF with 44 topology in 5 based on H3IDC is created. Complex 6 shows a 3D coordination framework containing 1D alternately arranged hydrophilic channels including (H2O)4 clusters and hydrophobic channels partially occupied by ethyl groups from imidazole rings, in which the Cd­(II) ion is viewed as a 4-connected node, and HIEDC2– and μ2-O are regarded as two different linkers, 6 showing 42·84 topology. Obviously, these results reveal that the existence of the substitute groups of 2-position in such 4,5-imidazoledicarboxylate ligand plays a critical role in the structural direction of these MOFs. Meanwhile, the adsorption and photoluminescent properties of the selected compounds are investigated.

Two Schiff base ligands (HL1, HL2) were synthesized as fluorescent sensors for Zn2+ or Cd2+. With an ethoxyl group, HL1 can distinguishingly sense Zn2+ and Cd2+, while HL2 exclusively responds to Zn2+.

One convenient Cd II -mediated C−C/C−N bond-forming strategy toward asymmetric tetra-(2-pyridine)substituted imidazolidine (L 1 ), the basic framework of several natural products with bioactivity, has been found for the first time. In the reaction of tridentate N3-set neutral pyridine-type Schiff base ligand (L) possessing a [−HCNCH 2 −] linkage with CdCl 2 at 70 °C for 3 days, one two-dimensional 4 4 topological layer [Cd 3 L 1 Cl 6 ] n (1) could be obtained, in which ligand L 1 resulted from [3 + 2] C−C/C−N asymmetric coupling dimerization of L. When equimolar amounts of NaSCN and NaNO 3 were added to the reaction mixtures, one-dimensional chain [Cd 2 L 1 (SCN)Cl 3 ] n (2) and zero-dimensional dinuclear Cd 2 L 1 (NO 3 ) 4 (MeOH) ( 3) containing the same ligand L 1 were also generated under the same reaction conditions, respectively. Obviously, the medium of the Cd 2+ ion plays the key role in solvothermal in situ formation of ligand L 1 . Moreover, new ligand tetra-substituted imidazolidine (L 1 ) could be obtained effectually from all three complexes 1−3 through the reactions of those compounds with Na 2 S.

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