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 1−8 are also investigated in the solution or solid state.