HYDROXAMIC ACID-DERIVATIVES OF PHENYLALANINE, TYROSINE AND 3,4-DIHYDROXYPHENYLALANINE (DOPA) AS LIGANDS

The systems cobalt(II), zinc(II), nickel(II) and copper(II) with phenylalaninehydroxamic acid (Pheha), tyrosinehydroxamic acid (Tyrha) and 3, 4-dihydroxyphenyIalaninehydroxamic acid (Dopaha) have been investigated by means of pH-metric, spectrophotometric and e.s.r. methods. Formation constants and assumptions concerning binding modes for complexes in aqueous solution are reported. Effects of the phenyl and hydroxyl groups on complex formation have been evaluated. Because of the phenyl group, the ligands and neutral species have quite poor solubility. Precipitates occur in many of the systems studied. Tyrha forms protonated complexes containing the hydroxy group in the protonated form. Catecholatetype (O, O) chelates can be assumed for copper(II)-Dopaha and zinc(II)-Dopaha above ca pH 9.5. © 1991, Taylor & Francis Group, LLC. All rights reserved.