Abstracts 2007

Abstract of Publication No. 580

Journal Cover Picture (PDF) Satoshi Koizumi, Masayuki Nihei, Takuya Shiga, Motohiro Nakano, Hiroyuki Nojiri, Roland Bircher, Oliver Waldmann, Stefan T. Ochsenbein, Hans U. Güdel, Felix Fernandez-Alonso and Hiroki Oshio
A Wheel-Shaped Single-Molecule Magnet of [MnII3MnIII4]: Quantum Tunneling of Magnetization under Static and Pulse Magnetic Fields
Chem. Eur. J. 13, 8445-8453 (2007)      Full Text (PDF)      DOI-Link      Journal Cover Picture      Journal Cover Picture (PDF)      DOI-Link     

Abstract: The reaction of N-(2-hydroxy-5-nitrobenzyl)iminodiethanol (=H3(5-NO2-hbide)) with Mn(OAc)2·4 H2O in methanol, followed by recrystallization from 1,2-dichloroethane, yielded a wheel-shaped single-molecule magnet (SMM) of [MnII3MnIII4(5-NO2-hbide)6]·5 C2H4Cl2 (1). In 1, seven manganese ions are linked by six tri-anionic ligands and form the wheel in which the two manganese ions on the rim and the one in the center are MnII and the other four manganese ions are MnIII ions. Powder magnetic susceptibility measurements showed a gradual increase with cmT values as the temperature was lowered, reaching a maximum value of 53.9 emu mol–1 K. Analyses of magnetic susceptibility data suggested a spin ground state of S=19/2. The zero-field splitting parameters of D and B were estimated to be -0.283(1) K and -1.64(1)×10–5 K, respectively, by high-field EPR measurements (HF-EPR). The anisotropic parameters agreed with those estimated from magnetization and inelastic neutron scattering experiments. AC magnetic susceptibility measurements showed frequency-dependent in- and out-of-phase signals, characteristic data for an SMM, and an Arrhenius plot of the relaxation time gave a re-orientation energy barrier (DE) of 18.1 K and a pre-exponential factor of 1.63×10–7 s. Magnetization experiments on aligned single crystals below 0.7 K showed a stepped hysteresis loop, confirming the occurrence of quantum tunneling of the on magnetization (QTM). QTM was, on the other hand, suppressed by rapid sweeps of the magnetic field even at 0.5 K. The sweep-rate dependence of the spin flips can be understood by considering the Landau-Zener-Stückelberg (LZS) model.

Cover Picture: A Wheel-Shaped Single-Molecule Magnet of [MnII3MnIII4]: Quantum tunneling of magnetization under static and pulse magnetic fields in a Mn7 wheel-shaped single-molecule magnet has been investigated. In their Full Paper on page 8445 ff., H. Oshio et al. present their latest result in this exciting field of nano-sized magnetic materials.

Last modified: 13.12.11 by Gabriela Frei