Physical and chemical properties of selected metal complexes of gossypol

Abstract

Abstract In order to understand the chemistry of complexes of gossypol several metal ion‐gossypol complexes have been synthesized. They do not melt below 300 C and turn dark in color after drying in a vacuum oven. The stability constants and stoichiometry of CO ++ , Ni ++ and Cu ++ gossypol complexes have been established by several analytical and spectroscopic techniques. The infrared spectra of solid samples show a greatly diminished absorption at 2.8µ and the 6.2µ band is shifted to a lower wavelength indicating binding of the metal through the hydroxyl and aldehyde groups. Electronic absorption spectra also support this conclusion. Bis(o‐carboxyphenylimino) gossypol gives a copper (II) complex, where the carboxylic group, but not the phenolic hydroxyl group, of the gossypol is ionized. In this instance copper ion is bound to the carboxy oxygen and nitrogen of the imine.