title: Synthesis, structural, and magnetic studies on a redox family of tetrametallic vanadium clusters: {VIV4}, {VIII2VIV2}, and {VIII4} butterfly complexes.
abstract: The synthesis, crystal structures, and magnetic properties are reported for a redox family of butterfly-type tetrametallic vanadium alkoxide clusters, namely [V2(VO)2(acac)4(RC{CH2O}3)2] (R=Me 1, Et 2, CH2OH 3), [V2(VO)2(acac)2(O2CPh)2(MeC{CH2O}3)2] (5), [(VO)4(MeOH)2(O2CPh)2({HOCH2}C{CH2O}3)2] (6), [V4Cl2(dbm)4(RC{CH2OH}3)2] (R=Me 7, Et 8, CH2OH 9), and [V4Cl2(dbm)4(MeO)6] (10). The cluster cores are {VIV4} (6), {VIII2VIV2} (1-5), and {VIII4} (7-10), with examples of both isomeric forms of the of the mixed-valence cores (either VIII or VIV ions forming the butterfly body). Magnetic studies reveal the clusters to be dominated by antiferromagnetic exchange interactions in each case. The magnetic exchange parameters are determined for representative examples of each core type. {VIV4} and {VIII4} have diamagnetic ground states. The two isomeric {VIII2VIV2} types are found to give rise to either an S=0 ground state with a number of low-lying excited states due to competing antiferromagnetic exchange interactions (VIII2 butterfly body) or to a well-isolated S=1 ground state (VIV2 butterfly body).
authors.affiliation: School of Chemistry, The University of Manchester, Manchester M13 9PL, UK.
authors.forename: Ian S
authors.initials: IS
authors.lastname: Tidmarsh
authors.forename: Emma
authors.initials: E
authors.lastname: Scales
authors.forename: Paul R
authors.initials: PR
authors.lastname: Brearley
authors.forename: Joanna
authors.initials: J
authors.lastname: Wolowska
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Sorace
authors.forename: Andrea
authors.initials: A
authors.lastname: Caneschi
authors.forename: Rebecca H
authors.initials: RH
authors.lastname: Laye
authors.forename: Eric J L
authors.initials: EJ
authors.lastname: McInnes