Seminar: George Christou – Københavns Universitet

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The Power of Molecular Chemistry in Nanoscale Materials Research

George Christou

Department of Chemistry, University of Florida, Gainesville, FL 32611, USA

Email: christou@chem.ufl.edu

Molecular chemistry can bring many powerful advantages to the study of nanoscale materials of various kinds, and this area of ‘molecular nanoscience’ is therefore a rapidly growing field. The advantages include monodisperse (single-size) products and a shell of organic ligation that imparts solubility and crystallinity, allowing structural characterization to atomic resolution by X-ray crystallography. The ligands can usually also be modified as desired, allowing tuning of redox properties and atom/isotope labelling (e.g. 2H, 19F, etc.) for various studies in solution and the solid state, such as NMR spectroscopy.

In the molecular nanomagnetism arena, the above advantages have been absolutely crucial in the study of single-molecule magnets (SMMs), individual molecules that function as nanoscale magnets. They have greatly assisted the synthesis and structural characterization of numerous SMMs, and they have led to discovery of new quantum physics phenomena important to new 21st century technologies. These include quantum tunneling of the magnetization vector, and quantum superposition/entanglement states, phenomena that could not be reliably detected from the study of traditional nanoparticles. Our giant (~4 nm) SMMs have also bridged the gap between the ‘top-down’ world of traditional magnetic nanoparticles and the ‘bottom-up’ world of molecular nanomagnets. In more recent work we have also been developing controlled ways to form supramolecular oligomers of 2 or more weakly-linked SMMs to study the quantum properties more deeply, and for the first time in solution.

More recently still, we have extended our molecular approach to other interesting materials and have been targeting molecular clusters that can be considered ‘molecular nanoparticles’ of certain metal oxides, such as cerium(IV) dioxide, and mixed-metal oxides with the perovskite structure. As part of this work, we have been developing routes to coordination cages with a second metal type inside, analogous to the perovskite repeating unit in AMnO3 (A = lanthanide or main group metal) perovskites, as well as developing new 3d metal-oxo catalysts for water oxidation. The syntheses, structures, and properties of a selection of these materials will be described.