Raman spectral titration method: an informative technique for studying the complexation of uranyl with uranyl(vi)–DPA/oxalate systems as examples

Abstract

The Raman band at about 870 cm originating from the symmetric stretch vibration (ν) of uranyl, UO, has proven to be very informative for investigating the complexation of uranyl using perchlorate or nitrate of known concentration as internal standards. The concentration of uranyl can be conveniently calculated by using the ratio of the directly read band intensities of uranyl and the added reference, ClO, with a factor of 1.72. While with NO of concentration lower than 1.8 M as the reference, a factor of 0.85 should be used. Furthermore, with added internal standards, the linear relationship between the Raman intensity and the concentration of the corresponding species is illustrated by the spectral titration of U(vi) with a very strong ligand, dipicolinic acid (DPA); and the application of a spectral titration method with Raman spectroscopy in studying the complexation of uranyl is demonstrated by the titration of U(vi) with oxalate. The stepwise changes in the Raman shift of 18, 17, and 6 cm, corresponding to the three oxalate anions successively bonding to UO, imply that the coordination modes are different. In the 1 : 1 and 1 : 2 ratios of metal to ligand complexes, the oxalate anions bond to the uranyl ion in side-on bidentate mode, but in the 1 : 3 complex the third oxalate bonds in head-on mode, which is much weaker than the first two.

Spectroscopic Study on Aqueous Uranyl(VI) Complexes with Methoxy- and Methylbenzoates: Electronic and Steric Effects of the Substituents

“…A linear background baseline was employed in the spectral region, and the uranyl peak was fitted with the Voigt profile. As a consequence, the center of the uranyl peak was determined to be 870 cm –1 , and a fwhm was also calculated to be 10 cm –1 , which are perfectly consistent with the previously reported Raman properties of the free uranyl ions. − …”

Complexation of uranyl(vi) with succinimidedioxime in comparison with glutarimidedioxime

“…The concentrations of uranium and free acid in the stock solution were verified by UVvisible absorption spectroscopy (Agilent Cary 7000) and Raman spectroscopy (Renishaw inVia). 31,32 For experimental details, see the ESI. † Other chemicals were of analytical grade or higher.…”

Novel Heterometallic Uranyl-Transition Metal Materials: Structure, Topology, and Solid State Photoluminescence Properties

“…These features may arise from the significant oligomerization, which has been shown to red-shift uranyl emission. 46 The decay could be fit with a biexponential model with lifetime values of 0.0056 and 0.093 ms. Although we hesitate to comment on a well-defined luminescent lifetime trend across the five compounds (1−4, and 6), owing to the variation in uranyl and secondary metal center local coordination spheres, we do observe significantly decreased lifetimes in compounds which contain a secondary transition metal center.…”

“…The spectrum is significantly red-shifted (by 21.5 nm) with respect to the uranyl nitrate salt, and the peaks are broader when compared to the other compounds in this study. These features may arise from the significant oligomerization, which has been shown to red-shift uranyl emission . The decay could be fit with a biexponential model with lifetime values of 0.0056 and 0.093 ms.…”