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 (H(2)L(1)) and ferrocenecarboxylic acid (HL(2)). Reactions the ligand H(2)L(1) with copper(II) and nickel(II) salts, in the presence of pyridine, give a tetranuclear Cu(2)Fe(2) mixed-metallic box Cu(2)L(1)(2)(Py)(2)(DMF)(2)(H(2)O)(2) (1) and a tetranuclear heterobimetallic helix Ni(2)L(1)(2)(Py)(4)(H(2)O) (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 H(2)L(1) with lanthanide ions afford two-dimensional networks [La(2)L(1)(3)(CH(3)OH)(4)]( infinity ) (3), [Eu(2)L(1)(3)(H(2)O)(5)]( infinity ) (4), and [Gd(2)L(1)(3)(CH(3)OH)(2)(H(2)O)(3)]( infinity ) (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 L(1) 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 Ln(2)L(2)(6)(CH(3)OH)(2)(H(2)O)(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.