A theoretical investigation into the 1,3-dipolar cycloaddition of azidotrimethylsilane onto nanographene

The mechanism of the 1,3-dipolar cycloaddition reaction of azidotrimethylsilane (ATS) onto nanographene (NG) is thoroughly investigated at the B3LYP/6-31G(d,p) level. Calculations reveal that the reaction occurs through a two-step reaction mechanism. The first step is the chemical adsorption and the second one is the decomposition of the thereby formed nitride upon thermal activation, giving rise to an N-bridged product ultimately. The latter is the rate-determining step. Two possible pathways are compared to show that the [3+2] channel is favored over the [3+4] channel. The former is a symmetric synchronous process, whereas the latter follows an asymmetric concerted way, which can be rationalized by means of the frontier molecular orbital (FMO) theory. The reactivity of NG is discussed in detail, revealing that it is the electron density at the functionalization site which dominates the reactivity rather than the energetic effect. As a result, the edge area is calculated to be much more reactive than the centre.