Spectroscopic investigation of indole-3-acetic acid interaction with iron(III)

FeIII was found to be gradually reduced by indole-3-acetic acid (IAA) in slightly acidic nitrate solution with further re-oxidation of the resulting FeII upon drying in air, which is reasoned to be of ecological significance considering IAA excretion by many soil micro-organisms. FeIII–IAA complex was isolated; its composition, some physicochemical properties and structural aspects were studied using Mossbauer, FTIR spectroscopic and other techniques. Possible influence of FeIII coordination on the redox properties of the ligand is also considered from the viewpoint of the nature of the bonding system which involves the conjugated π-electronic system of the pyrrole cycle along with the carboxylic O-donor atom.