EUROPIUM(III) COMPLEXES OF POLYFUNCTIONAL CARBOXYLIC ACIDS - LUMINESCENCE PROBES OF POSSIBLE BINDING SITES IN FULVIC ACID

摘要

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. (C) 1997 Academic Press. [References: 21]