title: Structure and bonding of the vanadium(III) hexa-aqua cation. 1. Experimental characterization and ligand-field analysis.
abstract: Spectroscopic and crystallographic data are presented for salts containing the [V(OH(2))(6)](3+) cation, providing a rigorous test of the ability of the angular overlap model (AOM) to inter-relate the electronic and molecular structure of integer-spin complexes. High-field multifrequency EPR provides a very precise definition of the ground-state spin-Hamiltonian parameters, while single-crystal absorption measurements enable the energies of excited ligand-field states to be identified. The EPR study of vanadium(III) as an impurity in guanidinium gallium sulfate is particularly instructive, with fine-structure observed attributable to crystallographically distinct [V(OH(2))(6)](3+) cations, hyperfine coupling, and ferroelectric domains. The electronic structure of the complex depends strongly on the mode of coordination of the water molecules to the vanadium(III) cation, as revealed by single-crystal neutron and X-ray diffraction measurements, and is also sensitive to the isotopic abundance. It is shown that the AOM gives a very good account of the change in the electronic structure, as a function of geometric coordinates of the [V(OH(2))(6)](3+) cation. However, the ligand-field analysis is inconsistent with the profiles of electronic transitions between ligand-field terms.
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3000, Bern 9 Switzerland. tregenna@iac.unibe.ch
authors.forename: Philip L W
authors.initials: PL
authors.lastname: Tregenna-Piggott
authors.forename: David
authors.initials: D
authors.lastname: Spichiger
authors.forename: Graham
authors.initials: G
authors.lastname: Carver
authors.forename: Beatrice
authors.initials: B
authors.lastname: Frey
authors.forename: Roland
authors.initials: R
authors.lastname: Meier
authors.forename: Høgni
authors.initials: H
authors.lastname: Weihe
authors.forename: John A
authors.initials: JA
authors.lastname: Cowan
authors.forename: Garry J
authors.initials: GJ
authors.lastname: McIntyre
authors.forename: Gernot
authors.initials: G
authors.lastname: Zahn
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Barra