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Santiago, Chile

Venegas-Yazigi D.,University of Santiago de Chile | Munoz K.,University of Santiago de Chile | Saldias M.,Estacion Central | Saldias M.,University of Chile | And 12 more authors.
Inorganica Chimica Acta

The magnetic properties of [(VO)3(μ-PO4) 2(2,2′-bpy)(μ-OH2)]1/3H2O (1) and (VO)2H4P2O9 (2), a tubular and a layered vanadium(IV) phosphates containing triply oxido bridged VIV dimers, are analyzed considering the Bleaney-Bowers S = 1/2 dimer model. In compound 1 the presence of an additional VIV connected with the VIV dimers through μ1,2-PO4 3- bridges is described with a Curie-Weiss type correction. This model reproduces the magnetic properties of compound 1 with g = 1.956, Jdim = -102.1 cm-1, θ = -0.4 cm-1 and Nα = 278 × 10-6 emu mol-1. In compound 2, the presence of a small percentage of paramagnetic impurity has to be considered to account for the divergence of χm at low temperatures. This simple model reproduces the magnetic data of compound 2 with g = 1.99, J = -62.4 cm -1 and a 1.2% of monomeric impurity. The moderate antiferromagnetic coupling found in the triply oxido bridges VIV dimers is justified from the structural parameters of the bridge. These studies confirm that the coupling through -O-P-O- bridges is antiferromagnetic and relatively weak, as well as previous magneto-structural correlations in this kind of oxido bridges. DFT calculations on a dinuclear fragment model for the two systems gave the following values of Jcalc = -72.4 cm-1 for 1 and J calc = -5.2 cm-1 for 2. These values reproduce the antiferromagnetic nature of the superexchange interactions between the V IV centers. © 2012 Elsevier B.V. All rights reserved. Source

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