title: Mixed-valent cobalt spin clusters: a hexanuclear complex and a one-dimensional coordination polymer comprised of alternating hepta- and mononuclear fragments.
abstract: Reactions between Co(OAc)2 and 2-amino-2-methyl-1,3-propanediol (ampdH2) afford a hexanuclear complex [Co6(H2O)(MeOH)(OAc)6(ampd)4] (1) and a one-dimensional coordination polymer comprised of discrete heptanuclear complexes covalently bound to mononuclear Co centers [Co8(H2O)2(OAc)7(ampd)6]n (2). While 1 is obtained under ambient reaction conditions, the formation of 2 requires solvothermal methods. Both products have been characterized crystallographically and found to be mixed-valent, containing divalent and trivalent Co centers. Down to 30 K, the variable-temperature magnetic susceptibility data of 1 and 2 are dominated by the single-ion properties of high-spin Co(II) centers with distorted-octahedral coordination geometries. Below this temperature, the effect of intramolecular ferromagnetic exchange interactions becomes apparent. The ferromagnetic coupling in 1 has been analyzed in terms of an anisotropic exchange model, and inelastic neutron scattering data are consistent with the proposed model. Although the structure of 2 precludes a quantitative interpretation, the magnetic data suggest ferromagnetic exchange within the heptanuclear unit and negligible interactions along the chain between the hepta- and mononuclear fragments.
authors.affiliation: School of Chemistry, University of Melbourne, Victoria 3010, Australia.
authors.forename: Kerwyn G
authors.initials: KG
authors.lastname: Alley
authors.forename: Roland
authors.initials: R
authors.lastname: Bircher
authors.forename: Oliver
authors.initials: O
authors.lastname: Waldmann
authors.forename: Stefan T
authors.initials: ST
authors.lastname: Ochsenbein
authors.forename: Hans U
authors.initials: HU
authors.lastname: Güdel
authors.forename: Boujemaa
authors.initials: B
authors.lastname: Moubaraki
authors.forename: Keith S
authors.initials: KS
authors.lastname: Murray
authors.forename: Felix
authors.initials: F
authors.lastname: Fernandez-Alonso
authors.forename: Brendan F
authors.initials: BF
authors.lastname: Abrahams
authors.forename: Colette
authors.initials: C
authors.lastname: Boskovic