title: Synthesis and spectroscopic characterization of a new family of Ni(4) spin clusters.
abstract: A new family of tetranuclear Ni complexes [Ni(4)(ROH)(4)L(4)] (H(2)L = salicylidene-2-ethanolamine; R = Me (1) or Et (2)) has been synthesized and studied. Complexes 1 and 2 possess a [Ni(4)O(4)] core comprising a distorted cubane arrangement. Magnetic susceptibility and inelastic neutron scattering studies indicate a combination of ferromagnetic and antiferromagnetic pairwise exchange interactions between the four Ni(II) centers, resulting in an S = 4 spin ground state. Magnetization measurements reveal an easy-axis-type magnetic anisotropy with D approximately -0.93 cm(-)(1) for both complexes. Despite the large magnetic anisotropy, no slow relaxation of the magnetization is observed down to 40 mK. To determine the origin of the low-temperature magnetic behavior, the magnetic anisotropy of complex 1 was probed in detail using inelastic neutron scattering and frequency domain magnetic resonance spectroscopy. The spectroscopic studies confirm the easy-axis-type anisotropy and indicate strong transverse interactions. These lead to rapid quantum tunneling of the magnetization, explaining the unexpected absence of slow magnetization relaxation for complex 1.
authors.affiliation: Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, CH-3012 Bern, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Sieber
authors.forename: Colette
authors.initials: C
authors.lastname: Boskovic
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: Grégory
authors.initials: G
authors.lastname: Chaboussant
authors.forename: Hans U
authors.initials: HU
authors.lastname: Güdel
authors.forename: Nadeschda
authors.initials: N
authors.lastname: Kirchner
authors.forename: Joris
authors.initials: J
authors.lastname: van Slageren
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wernsdorfer
authors.forename: Antonia
authors.initials: A
authors.lastname: Neels
authors.forename: Helen
authors.initials: H
authors.lastname: Stoeckli-Evans
authors.forename: Stefan
authors.initials: S
authors.lastname: Janssen
authors.forename: Fanni
authors.initials: F
authors.lastname: Juranyi
authors.forename: Hannu
authors.initials: H
authors.lastname: Mutka