Tetrametallic macrocyclic frameworks constructed from ferrocenedicarboxylato and 2,2′-bipyridine: synthesis, molecular structures and characteristics

Four novel tetranuclear macrocyclic compounds [Cd2(η2-O2CFcCO2)2(2,2′-bpy)2(H2O)2] · 2H2O (1), [Zn2(η2-O2CFcCO2)2(2,2′-bpy)2(H2O)2] · CH3OH · H2O (2), [Co2(O2CFcCO2)2(2,2′-bpy)2(μ2-OH2)2] · CH3OH · 2H2O (3), and [Ni2(O2CFcCO2)2(2,2′-bpy)2(μ2-OH2)2] · CH3OH · 2H2O (Fc=(η5-C5H4)Fe(η5-C5H4) (4) have been synthesized and structurally characterized by single crystal diffraction. The magnetic behaviors for compounds (3) and (4) are studied in the temperature range of 5.0–300 K. The results show that the antiferromagnetic coupling of CoII–CoII pairs occurs in (3), and unusual global ferromagnetic coupling between nickel (II) ions exists in (4). The solution-state differential pulse voltammetries of compounds (1)–(4) all show two peaks with large separations (ΔE) that indicate strong interactions between two ferrocene moieties. Their fluorescent and thermal properties were also investigated.