Mössbauer and FTIR spectroscopic studies of iron anthranilates: coordination, structure and some ecological aspects of iron complexation

The data on the coordination and structure of iron(II) and iron(III) anthranilates in the solid state and in aqueous medium are presented and discussed, as studied using Mossbauer (for solid products and frozen solutions) and FTIR spectroscopy (for solid samples). Whereas, in slightly acidic nitrate solutions under aerobic conditions ferric ions can still be gradually reduced by anthranilic (o-aminobenzoic) acid, which may have some ecological significance, in circumneutral media this process is retarded. Mossbauer parameters calculated for iron(II) and iron(III) anthranilates, as well as characteristic vibration modes of certain functional groups involved in coordination with iron cations are discussed. The FTIR data obtained for ferrous anthranilates, as compared to anthranilic acid, definitely exhibit the direct involvement of both the carboxylic and the amino groups of anthranilic acid in coordination with iron. q 1999 Elsevier Science B.V. All rights reserved.