On the Formation and Desolvation Mechanism of Organic Molecule Solvates: A Structural Study of Methyl Cholate Solvates

摘要

Solvate formation and the desolvation mechanism of 25 obtained methyl cholate solvates were rationalized using crystal structure analysis and study of the phase transformations. The facile solvate formation was determined to be associated with the possibility for more efficient packing in structures containing solvent molecules. Most of the obtained solvates crystallized in one of the six isostructural solvate groups, with solvent selection based on the solvent capability to provide particular intermolecular interactions along with appropriate size and shape. In crystal structures several different methyl cholate conformers were observed, as apparently more efficient packing could be achieved by diversifying the molecule conformation and even adopting energetically quite unfavorable conformations. Nevertheless, the packing was generally controlled by the steroid ring system, particularly employing hydrogen bonding of the attached hydroxyl groups. Study of the desolvation mechanism showed that the primary desolvation product is determined by the structure similarity with the solvate, with thermodynamic stability of the desolvate having no directly identifiable effect. In the case of the absence of an acceptable structurally similar desolvate, desolvation produced an amorphous phase.