Journal of Colloid and Interface Science, Vol.188, No.2, 439-443, 1997
Europium(III) Complexes of Polyfunctional Carboxylic-Acids - Luminescence Probes of Possible Binding-Sites in Fulvic-Acid
The F-7(0) --> D-5(0) excitation spectra of Eu(III) complexed with polyfunctional dicarboxylic acid containing neutral O, N, and S donors were investigated using Eu(III) luminescence spectroscopy. Three distinct peaks are seen in the excitation spectra in the Eu(III)-diglycolic acid (ODA) and Eu(III)-iminodiacetic acid (IMDA) systems showing the formation of three species, where each tridentate ODA(2-) and IMDA(2-) displace approximately three coordinated water molecules; however, the central S donor of Eu(III)-thiodiglycolate and 2,5-thiophenedicarboxylate are shown to be poor chelators for free Eu3+ ions. The neutral O and N donors in combination with neighboring carboxylates may form strong metal chelation sites on fulvic acid.