The magnetic molecules synthesis effort focuses on the design, the solution chemistry, and the generation and characterization of discrete and networked inorganic magnetic molecules. Driven by physics issues, the primary goal is to maintain systematic control over all parameters that determine the molecular magnetic microstructure (the discrete magnetic level spectrum), i.e. single-ion parameters (spin quantum numbers, interactions with the local environments, e.g. zero-field splitting and g tensor components), the intramolecular magnetic exchange and coupling of those local parameters, and the interaction between neighboring molecules (beyond the ubiquitous weak dipolar terms).

In our program, two classes of compounds are investigated: (1) Polyoxomolybdate and polyoxotungstate clusters that provide diamagnetic scaffold structures into which significant numbers of paramagnetic centers (e.g. 3d metal cations) can be integrated, and reduced polyoxovanadates that comprise magnetic vanadyl groups as their basic constituents.(2) Polynuclear coordination compounds based on various bridging organic ligands interconnecting paramagnetic centers.

Broad exploratory synthesis projects are essential to ultimately identify compounds with novel magnetic properties, and a large part of the synthesis effort aims at e.g. new synthesis routes, new building blocks for novel structures, etc. At the design stage, the synthesis task then identifies structural archetypes that are used to generate spin arrays with desired properties (symmetry, spin constituents, etc.). In certain cases attention is given to the development of similar derivatives of these systems in which certain parameters are varied. This can involve replacing magnetic centers or exchange ligands, structural modifications such as the change of coordination symmetries to induce change of local anisotropy, but also linking of the molecules in one, two, and three dimensions, i.e. introducing inter-molecular magnetic exchange, to e.g. monitor the onset of cooperative bulk properties. All products are isolated as single crystals to allow unambiguous structural characterization and to meet the requirements of the experimental studies of the substances’ physical properties; therefore the development and refinement of crystallization techniques becomes as important as the initial exploratory synthesis and the subsequent full chemical product characterization.

People and Collaborators

Main external collaborators:
Leroy Cronin, University of Glasgow, Glasgow, UK
Craig L. Hill, Emory University, Atlanta, GA
Achim Müller, University of Bielefeld, Bielefeld, Germany