title: Tetrametallic lanthanide(III) phosphonate cages: synthetic, structural and magnetic studies.
abstract: The synthesis, structures and magnetic properties of a family of lanthanide complexes containing phosphonate ligands are reported. Reaction of hydrated lanthanide nitrate and (t)butylphosphonic acid under reflux conditions in iso-butanol, in the presence of pivalic acid as a co-ligand produced five new lanthanide complexes; pyridine (py) was present as a base. The compounds formed are tetrametallic, with the general formula [pyH]4[Ln4(μ3-OH)(O3P(t)Bu)3(HO3P(t)Bu)(O2C(t)Bu)2(NO3)6] where Ln = Gd(III), 1; Tb(III), 2; Dy(III), 3; Ho(III), 4 and Er(III), 5. The metal sites within the complexes lie on the vertices of a triangle-based pyramid, with phosphonate ligands on the triangular faces linking the apical Ln site to the Ln sites in the base. Each lanthanide(III) site is eight-coordinate. Magnetic studies of the compounds show a decline in the product χ(M)T with T; modelling the behaviour of 1 shows anti-ferromagnetic exchange between Gd(III) centres within the triangle with a negligible interaction to the fourth Gd(III) centre at the apex of the trigonal pyramid.
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Oxford Road, Manchester M13 9PL, UK. richard.winpenny@manchester.ac.uk.
authors.forename: Karzan H
authors.initials: KH
authors.lastname: Zangana
authors.forename: Eufemio Moreno
authors.initials: EM
authors.lastname: Pineda
authors.forename: Richard E P
authors.initials: RE
authors.lastname: Winpenny