Abstracts 2007

Abstract of Publication No. 567

Ayuk M. Ako, Oliver Waldmann, Valeriu Mereacre, Frederik Klöwer, Ian J. Hewitt, Christopher E. Anson, Hans U. Güdel and Annie K. Powell
Odd-Numbered FeIII Complexes: Synthesis, Molecular Structure, Reactivity, and Magnetic Properties
Inorg. Chem. 46, 756-766 (2007)      Full Text (PDF)      DOI-Link      Supplementary Data (PDF)      Crystal Structure Data (CIF format)     

Abstract: A field-dependent inelastic neutron scattering (INS) experiment on an array of oriented single crystals of Mn12-acetate is reported. The experimental results provide clear evidence that the minority species observed in the INS spectra is the fast-relaxing species observed in, for instance, AC-susceptibility measurements. Three isostructural disklike heptanuclear FeIII compounds of the general formula [FeIII7(m3-O)3(L)3(m-O2CCMe3)6(h1-O2CCMe3)3(H2O)3], where L represents a di- or triethanolamine moiety, display a three-blade propeller topology, with the central Fe atom representing the axle or axis of the propeller. This motif corresponds to the theoretical model of a frustrated Heisenberg star, which is one of the very few solvable models in the area of frustrated quantum-spin systems and can, furthermore, be converted to an octanuclear cage for the case where L is triethanolamine to give [FeIII8(m4O)3(m4-tea)(teaH)3(O2CCMe3)6(N3)31/2MeCN·1/2H2O or [FeIII8(m4O)3(m4-tea)(teaH)3(O2CCMe3)6(SCN)3]·2MeCN when treated with excess NaN3 or NH4SCN, respectively. The core structure is formally derived from that of the heptanuclear compounds by the replacement of the three aqua ligands by an {Fe(tea)} moiety, so that the 3-fold axis of the propeller is now defined by two central FeIII atoms. Magnetic studies on two of the heptanulcear compounds established unequivocally S = 5/2 spin ground state for these complexes, consistent with overall antiferromagnetic interactions between the constituent FeIII ions.

Last modified: 13.12.11 by Gabriela Frei