Mechanical Preparation of Crystalline Materials. An Oxymoron?

In this chapter, we deal with the utilization of mechanochemical processes between molecular and ionic crystals to obtain new crystalline materials. Mechanochemical processes can be grossly divided into two categories depending on the bonding interactions involved: (i) breaking and forming of noncovalent bonds to yield supramolecular adducts (viz. cocrystals, salts, molecular complexes, host–guest systems, etc.)1 and (ii) breaking and forming of covalent bonds by the action of mixing reactants. These processes can take place in the course of a reaction between different molecular materials (intersolid) or within a molecular material (intrasolid). A third important class of reactions is that combining inter- and intrasolid processes that exploits supramolecular (mainly hydrogen bond driven) aggregation to link in space the reactants with the correct separation to allow subsequent covalent reaction, most often activated by UV radiation.