Aspartamide Polyhydroxamic Acids - Synthesis and Iron(III) Complexes

Several linear and cross-linked poly[a,P-C/V-hydroxy-D,L-aspartamide)] derivatives (polyhydroxamic acids) were synthesized by aminolysis of poly-D,L-(2,5-dioxo-l,3-pyrrolidinediyl) (polysuccinimide; PSI) with the corresponding hydroxylamines. Aminolysis of the succin- imide (SI) units in PSI with hydroxylamine or IV-methylhydroxy- lamine was either complete or only partial, depending on the molar ratio of the Si-units and the hydroxylamine. Copolymers with partially opened SI rings were subjected to further aminolysis by 2-ami- noethanol, di(2-hydroxyethyl)amine, butylamine, 2-phenylethy- lamine, 1,2-diaminoethane, and 1,6-diaminohexane. Use of diamines led to cross-linked polymers. Polyhydroxamic acids differed in the average relative molecular mass, the number and spacing between the hydroxamic acid groups and in their solubility. The polyhydroxamic acids formed colored complexes with the iron(III) ions. Stability constants for the iron(III)-poly[a,P-(N-hydroxy)-D,L- aspartamide] complexes were determined by spectrophotometric titration. Values of the equilibrium quotients at 25 °C were calculated and confirmed to be: Qj = (1.0 ± 0.4) x 102, Q% = (1.3 ± 0.7) x 10~2