The X-ray structure of the pyochelin Fe3+ complex.

By X-ray structure analysis it could be shown that from the solution equilibrium of pyochelin I and II, differing in the stereochemistry at C-2" (1a and 1b), crystals of the Fe3+ complex of the steroisomer 1a are formed with a 1:1 metal-to-ligand ratio. Ligand sites are the carboxylate and the phenolate anions and the two nitrogen atoms. Two equivalent ferri-pyochelin moieties are held together by a hydroxy and an acetate unit which satisfy the remaining two coordination sites of Fe3+.