Complexation-mediated crystallization

Abstract

Crown ether complexation solubilizes organic and inorganic salts in nonpolar media. Induction of crystallization from such solutions can result in crystallization of the free salt rather than the complex. This affords the opportunity to examine solvent effects on the crystallization of salts and other polar materials, leading to the modification of crystal shape and lattice. This approach, which we term complexation-mediated crystallization, has been applied to the crystallization of simple organic salts and to the formation of metal sulfides. The resulting crystal morphologies and structures are presented, as are the structures of an unusual potassium complex of 18-crown-6 and crown ether complexes of lead (11) acetate, hexaaquozinc(II), and aquo(trichloro)zinc(II).

Synthesis of anhydrous yttrium and rare earth vanadium oxides from aqueous solution

“…We briefly examined the possibility of crystal phase and/or habit modification through crystallization from nonaqueous solvents. 41 Sodium orthovanadate displays appreciable solubility only in water, but a ca. 0.033 M solution in methanol may be prepared through the addition of excess 18-crown-6 (ca.…”

Crystallization of Solid-State Materials via Decomplexation of Soluble Complexes

“…Introduction of aqueous sodium sulfide to an organic solution of mercuric chloride containing dibenzo-18-crown-6 afforded both β-HgS (metacinnabar) and α-HgS (cinnabar), the latter in the form of complex twinned crystals up to several millimeters in diameter . Alternatively, simply stirring the solid reactant salts as a suspension in an anhydrous organic solvent containing dibenzo-18-crown-6 can also afford crystalline products, with the crown ether essentially serving a catalytic role . In the most dramatic example, cubic-phase lead sulfide (galena) was obtained in nicely crystalline form from tetrahydrofuran (Figure ), whereas precipitation from water or other organic solvents under similar conditions afforded largely amorphous material.…”

“…Similar coordination modes appear to exist for yttrium(III) . Lead(II) acetate forms a sparingly soluble complex with dibenzo-18-crown-6 in which the lead ion, bearing two bidentate acetate groups and coordinated to each of the crown ether oxygens, displays a coordination number of 10. , …”

Crystallization of Solid-State Materials in Nonaqueous Gels. 1. Silver Bromide

“…Alteration of the crystallization solvent in the recrystallization of organic compounds often results in dramatic changes in crystal morphology . We have focused our attention on the crystallization of inorganic materials from nonaqueous solvents in order to attempt to exploit such solvent effects for the deliberate modification of their crystal form , we focus on the use of simple salt precursors, eliminating the need to synthesize and handle the requisite unstable and often costly and hazardous metal-organic precursors.…”

“…Aqueous gel crystallization techniques have been examined, , but to our knowledge, no studies of the crystallization of the silver halides (or any other solid-state inorganic materials) in nonaqueous gels have been reported. Although solubility of suitable precursor salts in nonaqueous solvents would appear to present a serious barrier to such studies, it is easily circumvented either by using appropriate salt/solvent combinations or by exploiting the ability of crown ethers and related chelating agents to solubilize inorganic salts even in quite nonpolar media. , …”