Surface modification of nanodiamond under Bingel-Hirsch conditions

The Bingel-Hirsch reaction consists in the reaction of a bromomalonate with electron-poor π bonds, for example, of carbon materials, yielding cyclopropane derivatives. The reactive nucleophile is generated in situ from the respective malonate using CBr(4) and a base. The resulting cyclopropane moiety links the carbon material's surface atoms covalently with the functional side groups of the malonate. So far, the reaction was limited to fullerenes and carbon nanotubes. Herein, we report on the first application of this reaction type for the surface modification of diamond nanoparticles. The surface of thermally annealed nanodiamond consists of fullerene-like sp(2) carbon atoms which exhibit a similar reactivity as those in the all-sp(2) carbon nanomaterials. It was found that the reaction proceeds smoothly and enables the grafting of a large variety of functional groups to the surface of nanodiamond. The generated nucleophiles are also able to react with carbonyl species on the diamond. This reaction pathway enables the grafting of malonates even on oxidized nanodiamond without prior thermal annealing.