Functional and Structural Characterization of Nanoparticulate Transition Metal Complexes Prepared Using Precipitation with Compressed Carbon Dioxide as an Antisolvent

Abstract

Nanostructures with novel size-dependent functional properties are rapidly emerging. In this dissertation, molecule-based nanoparticles of Cobalt-salen complexes were prepared from an organic solution of the compound using the precipitation with compressed antisolvent (PCA) technique. In situ X-ray absorption spectroscopy (EXAFS and XANES) in conjunction with quantitative microbalance techniques were employed to gain insight into the relationship between the structure and the gas binding ability of the nanoparticles. Unprocessed Co(salen), the starting material, was found to be of a square planar geometry and displayed no measurable binding for either dioxygen (O2) or nitric oxide (NO). In contrast, the Co(salen) nanoparticles with a distorted tetrahedral geometry showed near-stoichiometric O2 uptake as well as reactivity with NO. The nanoparticles were successfully coated on alumina supports using a Wurster-type coating device. These findings open new avenues for formation and novel applications of nanoparticulate metal complexes.