Hydrogen-abstraction reactions of fully hydrogenated silicon fullerene cages with the amino radical: a density functional study

Abstract

We applied density functional theory calculations to study reactions NH2 •+ SinHn fullerenes (n = 4, 6, 8, 10, 20, 24, 30, 36, and 50). The reactions between SinHn fullerenes and NH2 • radical are obtained to be exothermic, proceeding through a hydrogen-bonded prereactive complex. The resemblance between the structures of the reactants and the transition states indicates that the transition states appear earlier for the considered exothermic reactions. The calculated ΔH0 298 and ΔETS are in good correlation with the spherical excesses φi, showing upward trend with increasing curvature on silicon sites. The reactions of Si20H20 and Si20F20 with NH2 • and NF2 • radicals were also investigated. The reaction between Si20H20 and NF2 • radical also proceeds through a hydrogen-bonded prereactive complex. However, this reaction is endothermic, and as compared with the reaction of NH2 •+ Si20H20, the prereactive complex has stronger hydrogen bonding which leads to higher activation barrier. The reaction of Si20F20 and NF2 • radical as well as NH2 • radical is obtained to be endothermic, having significantly higher barriers via “late” transition states, in comparison to the reaction of NH2 •+ Si20H20.