Submitted to: Journal of Inclusion Phenomena and Macrocyclic Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2004
Publication Date: 2/1/2005
Citation: Dowd, M.K., Stevens, E.D. 2005. Inclusion complexes of gossypol with 2-pentanone, 3-pentanone and 2-hexanone. Journal of Inclusion Phenomena and Macrocyclic Chemistry. 51(1):65-71.
Interpretive Summary: Low temperature x-ray diffraction was used to study the structure of three new crystalline solvates of gossypol, a natural product of the cotton plant. In each compound, the gossypol and solvent molecules are in a 2:1 ratio, and the complex formed with 2-hexanone is different from all previously reported structures. The results will be of interest to scientists working to develop products based on gossypol unusual ability to form inclusion complexes with small molecular weight molecules.
Technical Abstract: Inclusion complexes of gossypol with 2-pentanone, 3-pentanone, and 2-hexanone were prepared by crystallization from the corresponding ketone and hexane, and their structures were determined by low-temperature x-ray diffraction. All three compounds crystallize in monoclinic systems and have a 2:1 gossypol-to-solvent molar ratio. Both pentanone complexes have C2/c space groups, and the solvent cages in these structures have C2 symmetry. The 3-pentanone molecule, which has C2 symmetry, sits symmetrically within the solvent site, and the 2-pentanone molecule, which lacks C2 symmetry, takes two equally probable orientations within the site. Both structures are similar to previously reported gossypol inclusion complexes formed with small esters and 3-hexanone. The distal positioning of the carbonyl group in 2-hexanone does not allow it to occupy the same solvent cage that exists in the pentanone structures. In the 2-hexanone complex, the solvent cages are skewed, and the C2 site symmetry is lost. As a result, the structure has a larger asymmetric unit and unit cell and a Cc space group. Although the 2-hexanone structure retains many of the features of the gossypol pentanone complexes, this is the first report of a gossypol inclusion compound with this extended cell structure.