Reto Basler, Colette Boskovic, Grégory Chaboussant, Hans U. Güdel, Mark Murrie, Stefan T. Ochsenbein and Andreas Sieber
Molecular Spin Clusters: New Synthetic Approaches and Neutron Scattering Studies
Chem. Phys. Chem. 4, 910-926 (2003)                                   

Abstract: We review our recent work in the field of molecular spin clusters and single-molecule magnets, showing how inelastic neutron scattering (INS) can be used to determine magnetic exchange interactions and anisotropy splittings. A general introduction to neutron scattering precedes selected examples, building upon the first determination of exchange coupling in a transition metal complex using INS, through anisotropic exchange in cobalt(II) spin clusters to the determination of exchange interactions in a dodecanuclear nickel(II) wheel. The strength of INS for the accurate determination of anisotropy splittings in single-molecule magnets is revealed. Not only can one determine the axial zero-field splitting parameter D, which plays a key role in single-molecule magnet behavior, but also higher-order terms important in understanding the quantum tunneling behavior. Finally, we review two of our synthetic approaches towards new single-molecule magnets based on nickel, manganese, and iron.

Cover Picture: The cover picture shows the principles of inelastic neutron scattering (INS) in magnetic molecular clusters. An incoming monochromatic neutron beam is scattered by a target sample (here a tetranuclear nickel(II) complex) both elastically (no energy transfer) and inelastically (positive or negative energy transfer). Scattered neutrons of varying velocity are then collected in detector banks that span a wide angular range. The interactions between the magnetic moments of the sample and the neutrons that occur during INS allow the investigation of the magnetic properties of the material and the accurate determination of the relevant parameters, including those associated with exchange interactions and magnetoanisotropy. This is nicely illustrated by the inelastic peaks, observed on both sides of the elastic line, which correspond to magnetic energy transfer between the neutrons and the sample. INS is a unique technique that affords a detailed insight into the magnetic levels over a large energy range (up to 1000 cm^–1) and thus can provide crucial information for a wide variety of magnetic materials.