title: Slow magnetic relaxation and charge-transfer in cyano-bridged coordination clusters incorporating [Re(CN)(7)](3-/4-).
abstract: Treatment of the cyanometalate building unit [Re(CN)(7)](3-) with [(PY5Me(2))M(MeCN)](2+) (M = Co, Ni, Cu) affords a series of pentanuclear clusters of formulas [(PY5Me(2))(4)M(4)Re(CN)(7)](5+) (M = Co, Ni, Cu) and [(PY5Me(2))(4)Cu(4)Re(CN)(7)](4+). Single crystal X-ray diffraction analyses of the clusters reveal a star-like structure in which four [(PY5Me(2))M](2+) moieties are linked to a central [Re(CN)(7)](3-) unit via bridging cyanide ligands. An intramolecular Co(II) → Re(IV) charge-transfer accompanies the formation of the Co(II)(4)Re(IV) cluster, giving a Co(II)(3)Co(III)Re(III) species. Spectroelectrochemical methods and irradiation experiments are used to characterize the metal-metal charge-transfer bands of this compound. A rhenium-based thermally induced one-electron reduction is observed for the Cu(II)(4)Re(IV) cluster to give a Cu(II)(4)Re(III) complex; however, this reduction may be forestalled at low temperature. Finally, magnetic measurements reveal intracluster ferromagnetic exchange coupling, strong uniaxial magnetic anisotropy, and slow magnetic relaxation in the Ni(II)(4)Re(IV) and Cu(II)(4)Re(IV) clusters.
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Zadrozny
authors.forename: Danna E
authors.initials: DE
authors.lastname: Freedman
authors.forename: David M
authors.initials: DM
authors.lastname: Jenkins
authors.forename: T David
authors.initials: TD
authors.lastname: Harris
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Iavarone
authors.forename: Corine
authors.initials: C
authors.lastname: Mathonière
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Clérac
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Long
mesh_terms: D008280:Magnetics; D008958:Models, Molecular; D009570:Nitriles / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012211:Rhenium / Q000737:chemistry*; D013237:Stereoisomerism; D013696:Temperature
chemical_list: D009570:Nitriles; D009942:Organometallic Compounds; D012211:Rhenium