A New and Unusual Iron-Oxo Core Topology using a Novel Hexadentate Chelate

A. Diodati, G. Christou, J. Peralta

University of Florida, Central Michigan University

The field of iron^III-oxo chemistry has found relevance that spans areas of ­molecular magnetism, single-molecule magnets, bioinorganic chemistry, and others. Small iron-oxo systems can be used as synthetic analogues of biomolecules such as methane monooxygenase, ribonucleotide reductase, and hemerythrin, as well as provide models to understand magnetic exchange couplings via magnetostructural correlations (MSCs), which can subsequently be utilized in modeling magnetic interactions in high nuclearity systems. Research in our group has involved the synthesis and study of a range of iron-oxo complexes of various nuclearities, and we have discovered clusters ranging from Fe₂ complexes up to an impressive Fe₃₆. We have found that the growth of iron-oxo clusters can be modulated by incorporation of a variety of different ligands and chelates, ranging from polyalcohols, polyamines, polypyridines, carboxylates and pseudo-carboxylates. In trying to expand our understanding of magnetic interactions and further probe the effectiveness of our MSCs, we have chosen to investigate new forms of organic chelates that could potentially provide new coordination environments and iron-oxo topologies. Herein we report the synthesis of a new ‘hybrid’ chelate that combines the attributes of a polyalcohol, polyamine, and polypyridine into one hexadentate ligand, yielding an iron-oxo cluster with, to our knowledge, an unprecedented tetranuclear topology. We shall describe our synthetic strategies, DFT computational results, MSC predictions, SQUID magnetic properties, and electron paramagnetic resonance studies.