Four Novel Frameworks Built by Imidazole-Based Dicarboxylate Ligands: Hydro(Solvo)thermal Synthesis, Crystal Structures, and Properties

Four novel complexes, {[Ni(4)(HEIDC)(4)(H(2)O)(8)].2H(2)O} (1), {[Mn(HEIDC)(4,4'-bipy)(0.5)(H(2)O)].H(2)O}(n) (2), [Mn(6)(EIDC)(4)(py)(H(2)O)(4)](n) (3), and {[Cd(2)(EIDC)(H(2)EIDC)(4,4'-bipy)(1.5)].H(2)O}(n) (4) (H(3)EIDC = 2-ethyl-1H-imidazole-4,5-dicarboxylic acid, 4,4'-bipy = 4,4'-bipyridine, and py = pyridine) have been hydro(solvo)thermally synthesized by fine control over synthetic conditions, such as solvent and pH value, and structurally characterized. It is shown through single-crystal X-ray diffractions that the ligands H(3)EIDC can be either singly, doubly, or triply deprotonated and can coordinate to Ni(II), Mn(II) or Cd(II) ions in mu(2) or mu(3) modes. Compound 1 is a zero-dimensional (0D) symmetrical tetranuclear molecular square. Compound 2 exhibits a two-dimensional (2D) sheet, in which alternate left- and right-handed helical chains are bridged by 4,4'-bipy linkages. Compound 3 assumes a 2D honeycomb-like sheet built up from mu(3)-EIDC(3-) and Mn(II) atoms. Compound 4 possesses a novel three-dimensional (3D) structure constructed from 2D layer motifs joined by mu(2)-HEIDC(2-) and 4,4'-bipy bridges. The thermal properties of complexes 1-4 have been determined as well. Also, it is discovered that there exists antiferromagnetic coupling between the Ni(II) or Mn(II) ions in 1 or 2 (3); the best fittings to the experimental magnetic susceptibilities gave J = -10.83 cm(-1) and g = 2.19 for 1, and J = -0.025 cm(-1), zJ' = -0.02 cm(-1) and g = 2.0 for 2.