Magneto-structural correlation studies of a ferromagnetically coupled dinuclear vanadium(IV) complex. single-crystal EPR study

Velayutham, Murugesan ; Varghese, Babu ; Subramanian, Sankaran (1998) Magneto-structural correlation studies of a ferromagnetically coupled dinuclear vanadium(IV) complex. single-crystal EPR study Inorganic Chemistry, 37 (6). pp. 1336-1340. ISSN 0020-1669

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Official URL: http://pubs.acs.org/doi/abs/10.1021/ic9707467

Related URL: http://dx.doi.org/10.1021/ic9707467

Abstract

The dimer potassium dioxo(citrato)vanadate(IV)-6-water, K4{VO[O2CCH2C(O)(CO2)CH2CO2]}2·6H2O, was prepared by the reaction of citric acid and metavanadate in a neutral solution. The complex crystallizes in the space group P with unit cell parameters a=8.474(5) Å, b=8.902(7) Å , c=9.596(9) Å , α=71.50(6)°,β= 70.81(9)°, γ=87.45(2)°, V=647.1Å 3, and Z=1. The dimeric anion contains a centrosymmetric planar four-membered V2O2 ring with the bridging oxygens derived from the hydroxyl groups. The configuration of the anion is anti-coplanar. A frozen solution EPR spectrum with zero-field splitting and 15 line hyperfine patterns on the parallel and perpendicular features characteristic of two equivalent vanadium atoms confirms the presence of a spin triplet. This is further supported by the presence of half-field "forbidden transition" at g ≈ 4. A broad line with half-field forbidden transitions in the powder EPR spectra at X,Q-bands of the neat sample and at different temperatures shows the presence of a spin triplet ground state and a very weak intermolecular dipolar interaction. From anisotropic exchange contributions to D the magnitude of the derived exchange integral Jxy,x2-y2 is 56 cm−1. UV-visible, ESCA, and theoretical BVS studies support the proposed molecular and electronic structure of the complex.

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