title: Proof of large positive zero-field splitting in a Ru2 5+ paddlewheel.
abstract: We present the synthesis, as well as the structural and magnetic characterization, of [Ru2(D(3,5-Cl2Ph)F)4Cl(0.5H2O)].C6H14 (D(3,5-Cl2Ph)F = N,N'-di(3,5-dichlorophenyl)formamidinate), a Ru2(5+) compound having a 4B(2u) ground state derived from a sigma2pi4delta2pi2delta electron configuration. The persistence of this configuration from 27 to 300 K is shown by the invariance of the Ru-Ru distance. Orientation-dependent magnetic susceptibility (chiT) and magnetization (M(H)) data are in accord with a spin quartet ground state with large magnetocrystalline anisotropy associated with a large axial zero-field splitting (D) parameter. Theoretical fits to chiT and M(H) plots yielded D/kB = +114 K, implying an S = +/-1/2 Kramers doublet ground state at low temperature. Single-crystal and powder EPR data are consistent with this result, as the only observed transition is between the M(s) = +/1/2 Zeeman levels. The g values are g(perpendicular) = 2.182, g(parallel) = 1.970, and D = 79.8 cm(-1). The totality of the results demands D >> 0.
authors.affiliation: Department of Chemistry, University of Miami, Coral Gables, Florida 33146, USA.
authors.forename: Wei-Zhong
authors.initials: WZ
authors.lastname: Chen
authors.forename: F Albert
authors.initials: FA
authors.lastname: Cotton
authors.forename: Naresh S
authors.initials: NS
authors.lastname: Dalal
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Murillo
authors.forename: Chris M
authors.initials: CM
authors.lastname: Ramsey
authors.forename: Tong
authors.initials: T
authors.lastname: Ren
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Wang
mesh_terms: D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D012428:Ruthenium