A Noyori-type ruthenium catalyst was immobilized on magnetic platforms consisting of carbon-coated cobalt nanoparticles and different polymers. Both reactivity and enantioselectivity of these catalysts were benchmarked in the asymmetric transfer hydrogenation of acetophenone in an aqueous medium. The best catalyst, having connected the ruthenium catalyst to the nanoparticle by a poly­(styrene) matrix, was characterized by infrared (IR) spectroscopy and via a superconducting quantum interference device (SQUID) to determine the saturation magnetization of the magnetic material as well as by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). A variety of aryl methyl ketones could be reduced to their corresponding alcohols with good yields (81–100%) and selectivity (91–99% ee), and catalyst recovery and reuse was evaluated over 10 runs with ruthenium leaching into the product of <10 ppm, meeting the pharmaceutical requirements for ruthenium impurities of orally available drugs.

Magnetic carbon-coated cobalt nanoparticles functionalized with polyethyleneimine proved to be highly effective and selective for the detoxification of mercury ions from aqueous solutions.

Ferromagnetic carbon-coated cobalt nanoparticles have been ligated by a covalent or non-covalent strategy with dendrons or polymers bearing amino-, hydroxy- or polyether-functionalities, aiming at synthesizing materials that are dispersible in aqueous solutions, being a prerequisite for applications in biomedicine. Most efficiently for this purpose proved to be a covalently anchored polyethyleneimine (PEI) with a loading of approximately 10 mmol of amino groups per gram of hybrid nanomaterial, resulting in dispersions that are stable in water for several days.

In magnetischen Nanopartikeln als Träger von Katalysatoren steckt noch viel ungenutztes Potenzial. Sie bilden eine Brücke zwischen homogener und heterogener Katalyse.