Functionalization of MonodisperseIron Oxide NPs andTheir Properties as Magnetically Recoverable Catalysts.

Here we report the functionalization of monodisperseiron oxidenanoparticles (NPs) with commercially available functional acids containingmultiple double bonds such as linolenic (LLA) and linoleic (LEA) acidsor pyridine moieties such as 6-methylpyridine-2-carboxylic acid, isonicotinicacid, 3-hydroxypicolinic acid, and 6-(1-piperidinyl)pyridine-3-carboxlicacid (PPCA). Both double bonds and pyridine groups can be reactedwith noble metal compounds to form catalytically active species inthe exterior of magnetic NPs, thus making them promising magneticallyrecoverable catalysts. We determined that both LLA and LEA stabilizemagnetic iron oxide NPs, allowing the formation of π-complexeswith bis(acetonitrile)dichloropalladium(II) in the NP shells. In bothcases, this leads to the formation of NP aggregates because of interparticlecomplexation. In the case of pyridine-containing ligands, only PPCAwith two N-containing rings is able to provide NP stabilization andfunctionalization whereas other pyridine-containing acids did nowallow sufficient steric stabilization. The interaction of PPCA-basedparticles with Pd acetate also leads to aggregation because of interparticleinteractions, but the aggregates that are formed are much smaller.Nevertheless, the catalytic properties in the selective hydrogenationof dimethylethynylcarbinol (DMEC) to dimethylvinylcarbinol were thebest for the catalyst based on LLA, demonstrating that the NP aggregatesin all cases are penetrable for DMEC. Easy magnetic separation ofthis catalyst from the reaction solution makes it promising as a magneticallyrecoverable catalyst. [ABSTRACT FROM AUTHOR]