Tetra-Mn-Containing 30-Tungsto-4-phosphate, [Mn(HO)(PWO)]: Synthesis, Structure, XPS, Magnetism, and Electrochemical Study.

Reaction of the mixed-valent Mn-acetato complex [MnMnO(CHCOO)(HO)] with the trilacunary Wells-Dawson-type heteropolytungstate [PWO] in acidic acetate solution (pH 1.1) resulted in the tetra-Mn-containing polyanion [Mn(HO)(PWO)] (). Single-crystal XRD on Na[Mn(HO)(PWO)]·84HO () revealed that four Mn ions form a rhombic MnO core encapsulated by two [PWO] units. X-ray photoelectron spectroscopy (XPS) data confirm the +3 oxidation state of the four manganese ions in . Magnetic measurements from 1.8-300 K in a 100 Oe magnetic field allowed for the extraction of full fitting parameters from the susceptibility data for . The negative value ( = -2.16 ± 0.08 K, = 3.24 ± 1.73 K, = 2.35 ± 0.040, and ρ = 0.34 ± 0.03) suggests a dominant antiferromagnetic spin exchange interaction between the four Mn ions, with the positive being an accompanying result of . Electrochemical studies revealed a reversible Mn/Mn redox couple in at the +0.80 to +1.1 V potential region with = +0.907 V.