The deep link between energy transfer and kinetics in mechanochemical reactions

Solid-state synthesis by mechanochemistry serves as an alternative to solution synthesis, but for a wider application within the framework of green chemistry, detailed investigations about reaction mechanisms at the molecular level are crucial [1]. One of current disadvantages of mechanochemistry is insufficient understanding of the influence of milling parameters on energy transfer during ball milling. In this paper, simple one-step trimerization of nickel(II) dibenzoylmethane was used as a model system to systematically examine by in situ Raman spectroscopy the effect of the milling frequency, and the material and mass of milling balls on the mechanochemical oligomerization reaction rate (Figure 1). By varying milling parameters, we have modified energy input required for the chemical transformation leading to different reaction profiles. Based on numerical simulations of the milling processes, a linear relationship was established between the reaction rate and the energy dose absorbed by the sample. Consequently, the energy dose increases with the frequency of impacts, mass and the average ball velocity, but decreases with the hardness of milling media to the minimum energy needed to initiate chemical conversion.