title: Studies of an enneanuclear manganese single-molecule magnet.
abstract: The reaction of [Mn(3)O(O(2)CMe)(6)(py)(3)] with the tripodal ligand H(3)thme (1,1,1-tris(hydroxymethyl)ethane) affords the enneanuclear complex [Mn(9)O(7)(O(2)CCH(3))(11)(thme)(py)(3)(H(2)O)(2)] 1.1MeCN.1Et(2)O. The metallic skeleton of complex 1 comprises a series of 10 edge-sharing triangles that describes part of an idealized icosahedron. Variable temperature direct current (dc) magnetic susceptibility data collected in the 1.8-300 K temperature range and in fields up to 5.5 T were fitted to give a spin ground state of S = (17)/(2) with an axial zero-field splitting parameter D = -0.29 cm(-)(1). Ac susceptibility studies indicate frequency-dependent out-of-phase signals below 4 K and an effective barrier for the relaxation of the magnetization of U(eff) = 27 K. Magnetic measurements of single crystals of 1 at low temperature show time- and temperature-dependent hysteresis loops which contain steps at regular intervals of field. Inelastic neutron scattering (INS) studies on complex 1 confirm the S = (17)/(2) ground state and analysis of the INS transitions within the zero-field split ground state leads to determination of the axial anisotropy, D = -0.249 cm(-)(1), and the crystal field parameter, B(4)(0) = 7(4) x 10(-)(6) cm(-)(1). Frequency domain magnetic resonance spectroscopy (FDMRS) determined the same parameters as D = -0.247 cm(-)(1) and B(4)(0) = 4.6 x 10(-)(6) cm(-)(1). DFT calculations are fully consistent with the experimental findings of two Mn(II) and four Mn(III) ions "spin up" and three Mn(IV) ions "spin down" resulting in the S = (17)/(2) spin ground state of the molecule, with D = -0.23 cm(-)(1) and U = 26.2 K.
authors.affiliation: School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh, EH9 3JJ, UK.
authors.forename: Stergios
authors.initials: S
authors.lastname: Piligkos
authors.forename: Gopalan
authors.initials: G
authors.lastname: Rajaraman
authors.forename: Monica
authors.initials: M
authors.lastname: Soler
authors.forename: Nadeschda
authors.initials: N
authors.lastname: Kirchner
authors.forename: Joris
authors.initials: J
authors.lastname: van Slageren
authors.forename: Roland
authors.initials: R
authors.lastname: Bircher
authors.forename: Simon
authors.initials: S
authors.lastname: Parsons
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Güdel
authors.forename: Jens
authors.initials: J
authors.lastname: Kortus
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wernsdorfer
authors.forename: George
authors.initials: G
authors.lastname: Christou
authors.forename: Euan K
authors.initials: EK
authors.lastname: Brechin