Turning over on sticky balls: preparation and catalytic studies of surface-functionalized TiO(2) nanoparticles

We have investigated the reactivity of rhodium(iii) complex-functionalized TiO(2) nanoparticles and demonstrate a proof-of-principle study of their catalytic activity in an alcohol oxidation carried out under aqueous conditions water in air. TiO(2) nanoparticles (NPs) have been treated with (4-([2,2′:6′,2′′-terpyridin]-4′-yl)phenyl)phosphonic acid, 1, to give the functionalized NPs (1)@TiO(2). Reaction between (1)@TiO(2) NPs and either RhCl(3)·3H(2)O or [Rh(2)(μ-OAc)(4)(H(2)O)(2)] produced the rhodium(iii) complex-functionalized NPs Rh(1)(2)@TiO(2). The functionalized NPs were characterized using thermogravimetric analysis (TGA), matrix-assisted laser desorption ionization (MALDI) mass spectrometry, (1)H NMR and FT-IR spectroscopies; the single crystal structures of [Rh(1)(2)][NO(3)](3)·1.25[H(3)O][NO(3)]·2.75H(2)O and of a phosphonate ester derivative were determined. (1)H NMR spectroscopy was used to follow the reaction kinetics and to assess the recyclability of the NP-supported catalyst. The catalytic activity of the Rh(1)(2)@TiO(2) NPs was compared to that of a homogeneous system containing [Rh(1)(2)](3+), confirming that no catalytic activity was lost upon surface-binding. Rh(1)(2)@TiO(2) NPs were able to withstand reaction temperatures of up to 100 °C for 24 days without degradation.