πbond versus radical character of the diamond(100)-2 X 1 surface

摘要

The dimers on clean diamond(100)-2 X 1 are linked by a σbond and a highly strained πbond causes the reactivity of this surface to be intermediate between that of an alkene and a bi-radical. We illustrate this behavior by investigating two prototypical cycloaddition surface reactions using multiple-internal-reflection infrared spectroscopy. Adsorption of 1,3-butadiene occurs via[4 + 2] addition to surface dimers, analogous to Diels-Alder chemistry of alkenes. However, [2 + 2] cycloaddition of cyclopentene, a reaction that is symmetry-forbidden with alkenes, occurred with a sticking coefficient of ～10~-3. These reactions illustrate novel approaches to the functionalization of diamond surfaces.