title: Single-molecule magnets: high-field electron paramagnetic resonance evaluation of the single-ion zero-field interaction in a Zn(II)3Ni(II) complex.
abstract: High-field electron paramagnetic resonance spectra were collected at several frequencies for a single crystal of [Zn3.91Ni0.09(hmp)4(dmb)4Cl4] (1), where dmb is 3,3-dimethyl-1-butanol and hmp- is the monoanion of 2-hydroxymethylpyridine. This crystal is isostructural to [Ni4(hmp)4(dmb)4Cl4] (2), which has been characterized to be a single-molecule magnet (SMM) with fast quantum tunneling of its magnetization (QTM). The single Ni(II) ion zero-field-splitting (zfs) parameters Di [= -5.30(5) cm(-1)] and Ei [= +/-1.20(2) cm(-1)] in the doped complex 1 were evaluated by rotation of a crystal in three planes. The easy-axes of magnetization associated with the single-ion zfs interactions were also found to be tilted 15 degrees away from the crystallographic c direction. This inclination provides a possible explanation for the fast QTM observed for complex 2. The single-ion zfs parameters are then related to the zfs parameters for the Ni4 molecule by irreducible tensor methods to give D = -0.69 cm(-1) for the S = 4 ground state of the SMM, where the axial zfs interaction is given by DS(Z)2.
authors.affiliation: Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California 92093-0358, USA.
authors.forename: En-Che
authors.initials: EC
authors.lastname: Yang
authors.forename: Cem
authors.initials: C
authors.lastname: Kirman
authors.forename: Jon
authors.initials: J
authors.lastname: Lawrence
authors.forename: Lev N
authors.initials: LN
authors.lastname: Zakharov
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold
authors.forename: Stephen
authors.initials: S
authors.lastname: Hill
authors.forename: David N
authors.initials: DN
authors.lastname: Hendrickson