Curium(III) and europium(III) complexation with multifunctional ligands investigated by time-resolved laser fluorescence spectroscopy.

摘要

This work describes the use of multifunctional ligands and their complexation to curium(III) and europium(III) in aqueous systems as a method to study the heavy metal interaction with a bacterial surface. The interactions between species of curium(III)/europium(III) and two phosphonocarboxylic acids and a series of additional ligands were studied using time-resolved laser fluorescence spectroscopy (TRLFS) and supported by 31P-NMR spectroscopy. Thermodynamic stability constants were determined for curium dihydrogen phosphonopropionate (CmH2PPA2+), curium hydrogen phosphonopropionate (CmHPPA+), curium dihydrogen phosphonoacetate (CmH2PAA2+), curium fluoropropionate (CmCF 3CH2COO2+) and curium difluoropropionate (Cm(CF 3CH2COO)2+) at an ionic strength of I = 0.05 M and a temperature of 25°C. These values are reported in logarithmic form and are 5.8 +/- 0.3, 6.5 +/- 0.5, 5.3 +/- 0.4, 5.9 +/- 0.3, 9.0 +/- 0.5, respectively. Fluorescence data, specifically peak 6.5 +/- 0.5, 5.3 +/- 0.4, 5.9 +/- 0.3, 9.0 +/- 0.5, respectively. Fluorescence data, specifically peak shifts and lifetime values, are reported for all of the complexation systems studied. Fluorescence spectra were analyzed using PEAKFIT (v 4.0) and ORIGIN. To support the fluorescence work, calculations using DFT were carried out on CmH 2PPA2+ and CmHPPA+, supporting the formation of a monodentate, phosphate bound complex and a bidentate, phosphate-carboxylate ring complex, respectively.;Thermodynamic acid dissociation constants were determined for 3-phosphonopropionic acid and phosphonoacetic acid in aqueous solution by potentiometry and supported by 31P NMR spectroscopy. The values for 3-phosphonopropionic acid are pKa1 = 1.69 +/- 0.06, pKa2 = 4.91 +/- 0.04, and pKa3 = 8.19 +/- 0.08. The values for phosphonoacetic acid are pKa1 = 1.96 +/- 0.03, pKa2 = 5.25 +/- 0.04, and pKa3 = 8.59 +/- 0.05. The constants were calculated at 25°C and extrapolated to infinite dilution (I = 0) using Specific Ion Interaction Theory (SIT).;Thorium(IV) and uranium(VI) complexation with Diphosil were investigated by small-angle x-ray scattering and anomalous small-angle x-ray scattering. The thorium-loaded and uranium-loaded material was heated to 1150°C in both 1°C and 5°C/minute increments. The nanophases formed by thorium-loaded Diphosil were larger than the uranium-loaded Diphosil at every temperature measured. At 1150°C, the thorium-loaded material had a mean radius of 100 A´ while the uranium-loaded material had a mean radius of 70 A´. Pore collapse was observed in both sets of samples.