Understanding the divergence in outcomes between mechanochemical and solution phase reactivity of fullerenes

Abstract

Here, we report a rationalization of the reaction between buckminsterfullerene, C60, and alkali metal cyanides, which has long been known to switch from an exclusive formation of the cyanofulleride anion when in solution to dimerization to C120 under ball-milling conditions. This striking divergence in selectivity has not been explained in a fully satisfactory way until now and has always remained an open question in mechanochemistry. In this work, we explore this computationally with density functional theory (DFT) and by microkinetically modeling the mechanism. Our results reproduce the experimentally observed complete switch in selectivity, finding that both products arise from the same mechanistic pathways and that the changes in concentration and dielectric constant of the environment are sufficient to reproduce the differences in the mechanochemical behavior. This work paves the way to a better understanding of other ball-milling reactions and an improved rational design of new mechanochemical reactions.