Magnetic and optical studies on an S=6 ground-state cluster [Cr12O9(OH)3(O2CCMe3)15]: Determination of, and the relationship between, single-ion and cluster spin Hamiltonian parameters

David Collison, Mark Murrie, Vasily S. Oganesyan, Stergios Piligkos, Nigel R. J. Poolton, Gopalan Rajaraman, Graham M. Smith, Andrew J. Thomson, Grigore A. Timko, Wolfgang Wernsdorfer, Richard E. P. Winpenny, Eric J. L. McInnes

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The dodecametallic Cr(III) cluster [Cr12O9(OH) 3(O2CCMe3)15] has a ground spin state of S = 6 characterized by the spin Hamiltonian parameters gzz = 1.965, gxx = gyy = 1.960, DS=6 = +0.088 cm-1, and E S=6 = 0 (where D and E are the axial and rhombic zero-field splitting parameters, respectively) as determined by multifrequency EPR spectroscopy and magnetization studies. Micro-SQUID magnetization studies reveal steps due to the fine structure of the ground state, with the spacing between the steps in excellent agreement with the DS=6 value determined by EPR. Analysis of high-resolution optical data (MCD) allows us to determine the single-ion g values and D value (= -1.035 cm-1) of the constituent Cr(III) ions directly. A vector coupling analysis demonstrates that the cluster ZFS is almost entirely due to the single-ion component. Thus, the relative orientations of the local and cluster magnetic axes can lead to a cluster ZFS of opposite sign to the single-ion value, even when this is the only significant contribution.

Original languageEnglish
Pages (from-to)5293-5303
Number of pages11
JournalInorganic Chemistry
Issue number17
Early online date26 Jul 2003
Publication statusPublished - 25 Aug 2003

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