A new hexanuclear Fe(III) nanocluster: synthesis, structure, magnetic properties, and efficient activity as a precatalyst in water oxidation

The oxo-bridged hexanuclear iron cluster formulated [Fe-6(III)(mu(4)-O)(2)(edteH)(2)(piv)(4)(SCN)(4)]center dot 2MeCN center dot 2H(2)O (1) (where edteH = N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine; piv = pivalic acid) has been synthesized by the reaction of FeCl2 center dot 4H(2)O with edteH(4) and piv in the presence of KSCN in CH2Cl2/MeCN. The single crystal X-ray measurements indicated that the cluster is centrosymmetric in structure. The magnetic study demonstrated the presence of very strong antiferromagnetic coupling between the iron centers and the Brillouin fitting showed the best fit with S = 5/2 and g = 1.87. In addition, the water oxidation activity of the cluster has been studied by electrochemical techniques. Electrochemical experiments revealed that the electrode modified by 1 has high efficiency for the oxidation of water and needs an overpotential of 484 mV under a constant current density of 15 mA cm(-2) with a Tafel slope of 114 mV dec(-1) in neutral media. Experiments indicated that in the presence of 1, a yellow solid film was formed on the electrode surface under the applied electrochemical conditions. This yellow material is likely a compound of iron and oxygen and has a crystalline nature. Our findings revealed that along with the cluster, this compound is active in water oxidation reactions.