Chemical Kinetics of the Mechanochemical Synthesis of Tetrathiafulvalene Chloranil

A large variety of materials can be prepared from powdered reactants by solid-state grinding and mechanochemistry, avoiding or largely reducing the use of reaction solvents, so offering alternative green chemistry synthetic routes. However, the mechanisms of such reactions are poorly understood, and their properties have only recently started to be unraveled. As part of a 2019 PURS project, our group studied the chemical kinetics of the mechanochemical synthesis of tetrathiafulvalene chloranil (green polymorph), a charge transfer complex with ionicity around 0.3e-. The electron transfer reaction between tetrathiafulvalene (electron donor) and chloranil (electron acceptor) was carried out by manually grinding stoichiometric quantities of the reactants in 1:1 molar ratio under isothermal conditions. The fraction of product obtained was monitored by quantitative phase analysis from laboratory X-ray powder diffraction using the internal standard method. Current results indicate a reaction order solid-state mechanism and a second-order rate law for the neat mechanochemical synthesis. An increased rate constant is observed for the same reaction by liquid-assisted grinding using diethyl ether as a liquid additive