Semiempirical Magnetostructural Correlation for High-Nuclearity Mn III -Oxo Complexes: Accommodation of Different Relative Jahn-Teller Axis Orientations.

The previous development of a magnetostructural correlation (MSC) for polynuclear Fe III /oxo clusters has now been extended to one for polynuclear Mn III /oxo clusters. A semiempirical model estimating each pairwise Mn 2 exchange constant ( J ij ) from the Mn-O bond lengths and Mn-O-Mn angles has been formulated based on the angular overlap model. The extra complication, compared with the Fe III /oxo MSC, of different relative orientations of the Jahn-Teller distortion axes typical of high-spin Mn III in near-octahedral geometry was accommodated by developing a separate MSC variant for each possible situation. The final coefficients of the three MSC variants were determined by using reliable crystal structure data and experimentally determined J ij values from the literature. The estimated J MSC values from the new Mn III /oxo MSC have been employed to successfully rationalize the magnetic properties of a number of Mn III clusters in the nuclearity range Mn 3 -Mn 10 . These properties include relative spin vector alignments in the ground state, the presence of spin frustration effects, and the resulting overall ground state spin. In addition, the J MSC values can be used to simulate the direct-current magnetic susceptibility versus temperature data and provide realistic input values for fits of these data to minimize false-fit problems. A protocol for the use of the new MSC is also reported.