Odd-Numbered Fe^III Complexes:  Synthesis, Molecular Structure, Reactivity, and Magnetic Properties

Abstract

Three isostructural disklike heptanuclear FeIII compounds of the general formula [FeIII7(mu3-O)3(L)3(mu-O2CCMe3)6(eta1-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(mu4O)3(mu4-tea)(teaH)3(O2CCMe3)6(N3)3].1/2MeCN.1/2H2O or [FeIII8(mu4O)3(mu4-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.

Collinear and Non-Collinear Configurations in Classical Geometrically Frustrated Ring-Shaped Systems

“…Continuous changes of configurations start (and end, in the case of centered rings) at the well-determined critical value of α, independent on system size for centered rings. It should to be stressed that these obtained for the second of models, |α c | 4, are identical as those found in their quantum counterparts [16,19,20]. Basing on numerical results, it can be said that the first critical value for quantum rings with a defect bond tends to calculated here α c 1{pn¡1q (see Fig.…”

“…The corresponding energies are ¡npα 2 {8 1q and ¡np|α|¡1q|, for |α| ¤ 4 and |α| ¥ 4, respectively. [16,19,20].…”

“…In this paper two such systems are presented: antiferromagnetic odd-numbered rings and rings with an even number of spins uniformly coupled to an extra one. The first case is related to the Cr 9 molecule [10], whereas the other is a model of Fe 7 or Gd 7 molecule [19,20]. In these cases there is a welldetermined domain with the collinear LEC despite the presence of frustration and this configuration is the same as in the absence of frustration.…”

Synthesis and characterisation of Fe6 and Fe12 clusters using bicine

“…complexes (R = Ph [10] or Me [11]). As bicine contains a carboxylate group in addition to the {N(CH 2 CH 2 OH) 2 } functionality this ligand should form new and interesting polynuclear Fe(III) clusters.…”

Synthesis, structure and magnetic properties of one chiral heptanuclear Fe cluster: {Fe[(FeL)2(μ2-OH)]3(μ2-OH)6}·13H2O

“…There is also a materials interest in that highnuclearity iron compounds can sometimes exhibit unusual and occasionally novel magnetic properties, with some of them even being examples of single molecule magnets (SMMs) [2]. At present, Fe clusters of nuclearity Fe 4 , Fe 6 , Fe 7 , Fe 8 , Fe 11 , Fe 12 , Fe 16 , Fe 19 , Fe 22 and others have been isolated, and their spectroscopic and magnetic properties have been investigated in considerable detail [3][4][5][6][7][8][9][10][11].…”