VIP Papers

Synthesis and Characterization of the Di-Copper(II)-Containing 22-Palladate(II), [CuII2PdII22PV12O60(OH)8]20-

Barsukova-Stuckart, M.; Izarova, N. V.; Jameson, G. B.; Ramachandran, V.; Wang, Z.; van Tol, J.; Dalal, N. S.; Ngo Biboum, R.; Keita, B.; Nadjo, L.; Kortz, U. Angew. Chem. Int. Ed. 2011, 50, 2639-2642. [Read Online]

ncontent_0 A couple of coppers: Two CuII ions exhibit highly distorted cubic coordination and  unexpectedly large magnetic exchange coupling in a discrete dicopper(II)-containing 22-  palladate(II). The compound is isolated as the hydrated sodium salt  Na20[CuII2PdII22PV12O60(OH)8]⋅58 H2O (1) in which the polyanion (see structure: Cu  turquoise, Pd blue, O red balls, {PO4} purple tetrahedra) is the largest noble metalate reported to date.



Nucleation process in the cavity of a 48-tungstophosphate wheel resulting in a 16 metal center iron-oxide nanocluster

Mal, S. S.; Dickman, M. H.; Kortz, U.; Todea, A. M.; Merca, A.; Bögge, H.; Glaser, T.; Müller, A.; Nellutla, S.; Kaur, N.; van Tol, J.; Dalal, N. S.; Keita, B.; Nadjo, L. Chem. Eur. J. 2008, 14, 1186-1195. [Read Online]

Fe16P8W48The 16-FeIII-containing 48-tungsto-8-phosphate [P8W48O184Fe16(OH)28(H2O)4]20− (1) has been synthesised and characterised by IR and ESR spectroscopy, TGA, elemental analyses, electrochemistry and susceptibility measurements. Single-crystal X-ray analyses were carried out on Li4K16[P8W48O184Fe16(OH)28(H2O)4]⋅66 H2O⋅2 KCl (LiK-1, orthorhombic space group Pnnm, a=36.3777(9) Å, b=13.9708(3) Å, c=26.9140(7) Å, and Z=2) and on the corresponding mixed sodium–potassium salt Na9K11[P8W48O184Fe16(OH)28(H2O)4]⋅100 H2O (NaK-1, monoclinic space group C2/c, a=46.552(4) Å, b=20.8239(18) Å, c=27.826(2) Å, β=97.141(2)° and Z=4). Polyanion 1 contains—in the form of a cyclic arrangement—the unprecedented {Fe16(OH)28(H2O)4}20+ nanocluster, with 16 edge- and corner-sharing FeO6 octahedra, grafted on the inner surface of the crown-shaped [H7P8W48O184]33− (P8W48) precursor. The synthesis of 1 was accomplished by reaction of different iron species containing FeII (in presence of O2) or FeIII ions with the P8W48 anion in aqueous, acidic medium (pH ≈4), which can be regarded as an assembly process under confined geometries. One fascinating aspect is the possibility to model the uptake and release of iron in ferritin. The electrochemical study of 1, which is stable from pH 1 through 7, offers an interesting example of a highly iron-rich cluster. The reduction wave associated with the FeIII centres could not be split in distinct steps independent of the potential scan rate from 2 to 1000 mV s−1; this is in full agreement with the structure showing that all 16 iron centres are equivalent. Polyanion 1 proved to be efficient for the electrocatalytic reduction of NOx, including nitrate. Magnetic and variable frequency EPR measurements on 1 suggest that the FeIII ions are strongly antiferromagnetically coupled and that the ground state is tentatively spin S=2.