Heterodimetallic Compounds Assembled from Ferrocenedicarboxylato and Ferrocenecarboxylato Ligands

Heteropolynuclear organometallic compounds have been constructed by using two kinds of ferrocene-based ligands, 1,1‘-ferrocenedicarboxylic acid (H2L1) and ferrocenecarboxylic acid (HL2). Reactions the ligand H2L1 with copper(II) and nickel(II) salts, in the presence of pyridine, give a tetranuclear Cu2Fe2 mixed-metallic box Cu2L12(Py)2(DMF)2(H2O)2 (1) and a tetranuclear heterobimetallic helix Ni2L12(Py)4(H2O) (2), respectively. In these complexes, the ferrocene moieties show cisoid conformations which lead to the formation of the finite coordination geometry, i.e. to molecular complexes. Interactions of the ligand H2L1 with lanthanide ions afford two-dimensional networks [La2L13(CH3OH)4] (3), [Eu2L13(H2O)5] (4), and [Gd2L13(CH3OH)2(H2O)3] (5), respectively, in which transoid conformations of the ferrocene moiety provide opportunities to form infinite 2-D networks. It is suggested that the conformational freedom of the ferrocene moiety makes the ligand L1 display different conformations and coordination modes in these complexes. In addition, the π···π interactions related to the ferrocene moieties were also found to stabilize the supramolecular architectures in the solid state. As a comparison, reaction of lanthanide ions with the ligand HL2 resulted in three isostructural heterodinuclear windmill-shaped compounds Ln2L26(CH3OH)2(H2O)5 [Ln = La (6), Eu (7), and Gd (8)] by simply diffusing the solutions of lanthanide ions into the mixture of HL2 and NaOH, respectively. Electrochemical properties of the ferrocene-containing complexes 18 are also investigated in the solution or solid state.