Intra-solid and inter-solid reactions of molecular crystals: A green route to crystal engineering.

The thesis developed in this chapter is that reactions taking place between mol. solids or within mol. solids, or involving a mol. solid and a vapor, can be exploited to "make new crystals", which is the quintessence of crystal engineering. Processes that lead from a cryst. reactant, or mixt. of reactants, to a cryst. product without the intervention of solvents will be discussed. The focus will be on solid-state reactions controlled primarily by supramol. bonding, such as template cycloaddns., formation of inclusion compds., reactions between mol. crystals via reassembling of non-covalent bonding, and formation of complexes and coordination compds. It is argued that solvent-free methods, e.g. co-grinding or milling of mol. solids, or reactions of solids with vapors represent viable "green" routes for the prepn. of novel mol. and supramol. solids