Engineered materials with tailored structures offer many potential applications due to their unique physicochemical properties.  Here we will show how the local structure and ligand environment of Co(salen) nanoparticles influences oxygen and NO binding properties, affecting the intrinsic catalytic properties of the materials.  The Co(salen) nanoparticles were prepared by the precipitation with compressed antisolvent (PCA) technique. The structure and ligand environment of Co(salen) nanoparticles were determined by the combined application of infrared, Raman, X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) spectroscopies, and X-ray diffraction (XRD) experiments before and during interaction with O2 (or NO).  The results indicate that the enhanced O2 (and NO) binding properties of Co(salen) nanoparticles are related to the unique distorted tetrahedral geometry, which is not observed in the unprocessed samples that contain mainly dimers with square planar geometry.  The Co(salen) nanoparticles show near-stoichiometric O2 adsorption, as demonstrated by microbalance gas binding experiments.  The spectroscopy results indicate the presence of CoII centers with distorted tetrahedral geometry in the Co(salen) nanoparticles with no evidence of metallic Co clusters, confirmed by the lack of Co-Co contributions at bonding distances in the EXAFS spectra and the presence of characteristic features of CoII in the XANES spectra.  The results presented here provide a fundamental relationship between active center structure and properties of novel molecule-based nanomaterials.

Structural requirements for O<sub>2</sub> and NO reactivity in Co(salen) catalysts

248th National Meeting (2014)

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Structural requirements for O2 and NO reactivity in Co(salen) catalysts

Structural requirements for O₂ and NO reactivity in Co(salen) catalysts