title: Nickel pivalate complexes: structural variations and magnetic susceptibility and inelastic neutron scattering studies.
abstract: The synthesis and structural characterisation of three small nickel(II) cages are reported, all stabilised by pivalate ligands. The magnetic properties of the cages have been studied by a combination of susceptibility measurements and inelastic neutron scattering. For a dinuclear cage, [Ni2(mu-OH2)(O2CCMe3)4(HO2CCMe3)4] 1 the ground state is S=2, with a ferromagnetic exchange interaction between the Ni(II) centres of J=0.32 meV and D(S=2)=-0.09 meV in the ground state. For a tetranuclear heterocubane cage, [Ni4(mu(3)-OMe)4(O2CCMe3)4(MeOH)4] 2, two ferromagnetic exchange interactions are found and an S=4 ground state observed. While the zero-field splitting of this state cannot be determined unambigiously the most likely value is DS=4=-0.035 meV. For a tetranuclear nickel butterfly, [Ni4(mu3-OH)2(O2CCMe3)6(EtOH)6] 3, three exchange interactions are required, two anti-ferromagnetic and one weakly ferromagnetic; the resulting ground state is S=0. The data enable us to estimate the zero-field splitting of single Ni(II) ions involved in the cage as Di=+1.0 meV. Both and are therefore expected to be new single molecule magnets.
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3000 Bern 9, Switzerland.
authors.forename: Grégory
authors.initials: G
authors.lastname: Chaboussant
authors.forename: Reto
authors.initials: R
authors.lastname: Basler
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Güdel
authors.forename: Stefan
authors.initials: S
authors.lastname: Ochsenbein
authors.forename: Andrew
authors.initials: A
authors.lastname: Parkin
authors.forename: Simon
authors.initials: S
authors.lastname: Parsons
authors.forename: Gopalan
authors.initials: G
authors.lastname: Rajaraman
authors.forename: Andreas
authors.initials: A
authors.lastname: Sieber
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Smith
authors.forename: Grigore A
authors.initials: GA
authors.lastname: Timco
authors.forename: Richard E P
authors.initials: RE
authors.lastname: Winpenny