Two Tetranuclear 3d-4f Heterometal Complexes Mn(2)Ln(2) (Ln = Dy, Gd): Synthesis, Structure, Magnetism, And Electrocatalytic Reactivity For Water Oxidation

In this present study, two Mn/Ln clusters, [Mn(2)Ln(2)(O2CMe)(6)(pdmH)(2)L](NO3)center dot H2O (Ln = Dy (1), Gd (2)), have been synthesized and experimentally investigated by X-ray crystallography, PXRD, magneto- and electrochemistry. By X-ray analysis, it is shown that the two complexes are isomorphous, both possessing one [Mn(II)Mn(III)Ln(2)(III) (mu(3)-O-2)(2)](6+) core with four metal atoms in one plane arranged in a butterfly conformation. This is the first time that mixed-valent manganese (Mn-II and Mn-III) and Ln(III) heterometal tetranuclear complexes have been isolated and characterized. Magnetic susceptibility measurements reveal that compounds 1 and 2 both display overall weak ferromagnetic exchanges between the metal ions within the clusters. The temperature dependencies of the out-of-phase (chi M') and in-phase (chi M') ac susceptibility signals exhibit no significant frequency-dependency for compounds 1 and 2, which suggests that the two complexes may not be SMMs. Electrochemical studies indicate that compounds 1 and 2 can both catalyze water oxidation at a potential of similar to 1.70 V with an overpotential of similar to 880 mV vs. NHE, which could be due to a cooperative catalytic effect between the manganese and lanthanide ions.