Secondary Ligand-Directed Assembly of Cd-II Coordination Architectures: From 0D to 3D Complexes Based on Ferrocenyl Carboxylate

To investigate the influence of spatial extended direction and flexibility of secondary ligand on the resulting structure, eight new ferrocene-containing complexes with various dimensionalities have been synthesized by the reactions of Cd-II salts and 1,1'-bis(3-carboxy-1-oxopropyl)ferrocene (H(2)bfcs) with series of rationally selected N-heterocyclic spacers. When the small organic molecule 4-aminopyridine (apy) was employed as a secondary ligand, a one-dimensional (1D) linear complex {[Cd(bfcs)(apy)(2)] center dot H2O}(n) (1) was furnished, while the use of bis(azole) bridging ligands resulted in the formation of a 1D ribbon complex {[Cd(bfcs)(bbbm)(1.5)] center dot CH3OH center dot 2H(2)O}(n) (2), a rare 1D quadruple-chain complex {[Cd(bfcs)(btmb)] center dot 3H(2)O)(n) (3) and two two-dimensional (2D) puckered complexes {[Cd-2(bfcs)(2)(pbbm)(2)]center dot 2H(2)O}(n) (4) and {[Cd(bfcs)(bix)]center dot H2O}(n) (5) (bbbm = 1,1'-(1,4- butanediyl)bis-1H-benzimidazole, btmb = 4,4'-bis(1,2,4-triazole-1-ylmethyl)biphenyl, pbbm = 1,1'-(1,3-propanediyl)bis-1H-benzimidazole, bix = 1,4-bis(imidazole-1 -ylmethyl)benzene). In addition, the tripodal bridging secondary ligand led to an unusual three-dimensional (3D) layer pillar complex {[Cd-2(bfcs)(titb)(2)Cl-2]center dot 2CH(3)OH center dot 4H(2)O}(n) (6) (titb = 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene). Employment of a flexible multidentate molecule tris(2-benzimidazolylmethyl)amine (ntb) as the secondary ligand gave birth to a mononuclear complex [Cd(bfcs)(ntb)]center dot DMF center dot 5H(2)O (7) and a binuclear complex [Cd-2-(bfcs)(ntb)(2)]center dot bfcs center dot 5H(2)O (8), in which ntb adopted the chelating coordination mode. It can be observed from the coordination architectures of 1-8 that secondary ligands had great effects on the spatial connective fashions of Cd-II centers, resulting in the formation of various dimensional complexes.