Heterodimetallic Compounds Assembled from Ferrocenedicarboxylato and Ferrocenecarboxylato Ligands

Heteropolynuclear organometallic compounds have been constructed by using two kinds of ferrocene-based ligands, 1,1ʹ-ferrocenedicarboxylic acid (HzU) and ferrocenecarboxylic acid (HU). Reactions the ligand H2Ll with copper(ll) and nickel(ll) salts, in the presence of pyridine, give a tetranuclear CuzFe2 mixed-metallic box Cu2L1(2)(Py)2(DMF)2(H2O)2 (1) and a tetranuclear heterobimetallic helix Ni2Ll2(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 HaU with lanthanide ions afford two-dimensional networks [La2L2(3)CH3OH)4] (3), [Eu1(3)(H2O)5] (4), and Gd2L1(3)(3CH3OH)2)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 Ll display different conformations and coordination modes in these complexes. In addition, the Pi...Pi 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 HL^2 resulted in three isostructural heterodinuclear windmill-shaped compounds Ln2L2(6)-(CH3OH)2(H2O)5 [Ln = La (6), Eu (7), and Gd (8)] by simply diffusing the solutions of lanthanide ions into the mixture of HL^2 and NaOH, respectively. Electrochemical properties of the ferrocene-containing complexes 1-8 are also investigated in the solution or solid state.