Synthesis, crystal structure and luminescent properties of a tetranuclear ferrocene-cadmium compound bearing a Cd4O4 cubane

The reaction of Cd(CH3COO)2·2H2O with di-2-pyridyl ketone (DPK) and FcCOONa in methanol-acetonitrile led to the formation of a tetranuclear ferrocene-cadmium compound [Cd4(η2-FcCOO)3(FcCOO)(DPD-OH)4]·2CH2Cl2·FcCOOH (Fc = (η5-C5H5)Fe(η5-C5H4), DPD-OH− = (2-Py)2C(OH)O−). In the compound three of the four coordinated ferrocenecarboxylates behave as chelating ligands, while the other one acts as a monodentate ligand. Each of them is linked to one Cd(II) ion via the coordination of the carboxylate group. The four Cd(II) ions mentioned above are further consolidated by four DPD-OH− anions functioning as η1:η3:η1:μ3 ligands to form a Cd4O4 cubane. The thus formed title compound shows a strong fluorescent emission at ca. 576 nm in the solid state.