TRANSITION METAL COMPLEXES AND NANO-PARTICLES ENTRAPPED IN SOL-GEL MATRICES AS ELECTRON EXCHANGE COLUMNS AND AS REDOX CATALYSTS

Sol-gel matrices can be used to entrap different compounds, mainly large compounds. The matrices thus prepared can act as catalysts, slow release agents, ion or electron exchange columns, and so on. One of the advantages of matrices thus prepared is that the entrapped catalyst/redox agent has not to be separated from the products at the end of the process, and can be easily recycled. The matrices can be used for a variety of purposes, an important one being in the field of waste treatment. Matrices thus prepared can operate in solvents in which the entrapped compound is insoluble. The major disadvantage of these matrices is that they tend to lose the entrapped species if it is not very large. This can be overcome by covalent binding of the entrapped compound to the matrix. Often the entrapped redox reagent in its active oxidation state is not stable in homogeneous solutions. Sol-gel matrices have been shown to stabilize unstable species, such as Ni-III(cyclam) by binding it to the matrix or by hindering its decomposition mechanism, e.g. a second order decomposition. Our results point out that Ag degrees and Au degrees nano-particles, as well as copper and nickel complexes entrapped in such a matrix show promise as redox catalysts and electro-catalysts. Furthermore, redox active complexes such as nickel complexes and polyoxometalates bound to/entrapped in such a matrix act as electron exchange columns.