Synthesis of new polymetallic iron(III) clusters containing polycarboxylate ligands based on cavity-blocked cyclen.

The synthesis and magnetic properties of enneametallic and octametallic Fe(III) cage complexes from tetraazamacrocycle ligands (1,7-H2DO2A) and (H3DO3A) respectively, are reported.

Dimethyl 2,2'-bipyridine-6,6'-dicarboxylate and bis(dimethyl 2,2'-bipyridine-6,6'-dicarboxylato-kappa2N,N')copper(I) tetrafluoroborate.

The single-crystal X-ray structures of dimethyl 2,2'-bipyridine-6,6'-dicarboxylate, C(14)H(12)N(2)O(4), and the copper(I) coordination complex bis(dimethyl 2,2'-bipyridine-6,6'-dicarboxylato-kappa(2)N,N')copper(I) tetrafluoroborate, [Cu(C(14)H(12)N(2)O(4))(2)]BF(4), are reported. The uncoordinated ligand crystallizes across an inversion centre and adopts the anticipated anti pyridyl arrangement with coplanar pyridyl rings. In contrast, upon coordination of copper(I), the ligand adopts an arrangement of pyridyl donors facilitating chelating metal coordination and an increased inter-pyridyl twisting within each ligand. The distortion of each ligand contrasts with comparable copper(I) complexes of unfunctionalized 2,2'-bipyridine.

Studies of an Fe9 tridiminished icosahedron.

The synthesis and structural characterization of a nonanuclear FeIII cage complex is reported. The nine iron centers in [Fe9(mu3-O)4(O3PPh)3(O2CCMe3)13] lie on the vertices of an incomplete icosahedron, with the P atoms of triphenylphosphonate at the other three vertices. The paramagnetic core therefore describes a tridiminished icosahedron. Magnetic studies suggest an S=1/2 ground state for the molecule. Analysis of exchange paths and the susceptibility data point to the interpretation that the cluster can be divided into two nearly decoupled sections: an {Fe6O3} section, with an S=0 ground state, in which three oxo-centered triangles bound a central triangle that is not oxo-centered; and an {Fe3O} triangle with S=1/2. The analysis of the susceptibility data leads to a Heisenberg model based on three significant antiferromagnetic exchange interactions, with values of 173.7 cm-1 in the {Fe3O} triangle, and 30.9 and 19.1 cm-1 within the {Fe6O3} section, while the exchange between them is <1 cm-1. With these assignments, the theoretical low-temperature differential susceptibility is also in very good agreement with measurements up to 50 T. Magnetic measurements in the milli-kelvin range reveal striking hysteresis loops and magnetization reversals associated with a Landau-Zener-Stückelberg (LZS) transition as enhanced by the occurrence of a phonon bottleneck.

A highly reduced vanadium(III/IV) polyoxovanadate comprising an octavanadyl square-prism surrounding a dimetallic vanadium(III) fragment.

The synthesis, crystal structure and preliminary magnetic studies are reported for a very highly reduced, VIV8VIII2, polyoxo(alkoxo)vanadate with a unique square prismatic topology.

Polynuclear vanadium complexes from thermal decomposition of [V3O(O2CPh)6(H2O)3]Cl.

Solid-state decomposition of [V3O(O2CPh)6(H2O)3]Cl at 300 degrees C followed by alcoholysis of the product gives the new vanadium complexes [V6O6(PhCO2)6(CH3O)6(CH3OH)3] (1), [V6O6(PhCO2)6(C2H5O)6(C2H5OH)3] (2), [V6O6(PhCO2)6(C3H7O)6(C3H7OH)3] (3), [V6O6(PhCO2)6(C4H9O)6(C4H9OH)3] (4) and [V4O4(OCH3)6(O2CPh)2(HOCH3)2] (5). Complexes 2, 3 and 5 have been crystallographically characterised. DC magnetic susceptibility studies on complex shows antiferromagnetic coupling leading to a S = 0 spin ground state.