Crystallization of Solid-State Materials via Decomplexation of Soluble Complexes

A variety of compounds which are at best sparingly soluble in aqueous media may be readily brought into solution through the formation of soluble coordination complexes. Modification of experimental conditions through, e.g., dilution or slow removal of the complexing agent, leads to supersaturation and, consequently, crystallization of the original solid-state phase. This technique of decomplexation crystallization, both of simple inorganic coordination complexes and of complexes with macrocyclic organic chelating agents, offers the opportunity both to effect the recrystallization of sparingly soluble species and to modify their crystal morphology. Similarly, precursors for solid-state materials may be solubilized in nonaqueous solvents through the formation of soluble complexes and then allowed to undergo reaction crystallization, allowing the examination of both solvent effects and chelation effects on the morphology and phase of the resulting solid-state materials. These effects are often dramatic, and such “complexation-mediated crystallization” approaches offer promise for the facile preparation of metastable phases from simple precursors under ambient conditions.