Synthesis and characterization of a novel aminopolycarboxylate complexant for efficient trivalent f-element differentiation: N-butyl-2-acetamide-diethylenetriamine-N,N',N'',N''-tetraacetic acid

The novel metal ion complexant N-butyl-2-acetamide-diethylenetriamine-N,N',N'',N''-tetraacetic acid (DTTA-BuA) uses an amide functionalization to increase the total ligand acidity and attain efficient 4f/5f differentiation in low pH conditions. The amide, when located on the diethylenetriamine platform containing four acetate pendant arms maintains the octadentate coordination sphere for all investigated trivalent f-elements. This compact coordination environment inhibits the protonation of LnL^- complexes, as indicated by lower K₁₁₁ constants relative to the corresponding protonation site of the free ligand. For actinide ions, the enhanced stability of AnL^- lowers the K₁₁₁ for americium and curium beyond the aptitude of potentiometric detection. Density functional theory computations indicate the difference in the back-donation ability of Am³⁺ and Eu³⁺ f-orbitals is mainly responsible for stronger proton affinity of EuL^- compared to AmL^-. The measured stability constants for the formation of AmL^- and CmL^- complexes are consistently higher, relative to ML^- complexes with lanthanides of similar charge density. When compared with the conventional aminopolycarboxylate diethylenetriamine pentaacetic acid (DTPA), the modified DTTA-BuA complexant features higher ligand acidity and the important An³⁺/Ln³⁺ differentiation when deployed on a liquid-liquid distribution platform.

A novel fluorescent probe (dtpa-bis(cytosine)) for detection of Eu(III) in rare earth metal ions

In this paper, a novel fluorescent probe, dtpa-bis(cytosine), was designed and synthesized for detecting europium (Eu³⁺) ion. Upon addition of Eu³⁺ ions into the dtpa-bis(cytosine) solution, the fluorescence intensity can strongly be enhanced. Conversely, adding other rare earth metal ions, such as Y³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Yb³⁺ and Lu³⁺, into dtpa-bis(cytosine) solution, the fluorescence intensity is decreased slightly. Some parameters affecting the fluorescence intensity of dtpa-bis(cytosine) solution in the presence of Eu³⁺ ions were investigated, including solution pH value, Eu³⁺ ion concentration and interfering substances. The detection mechanism of Eu³⁺ ion using dtpa-bis(cytosine) as fluorescent probe was proposed. Under optimum conditions, the fluorescence emission intensities of Eu^III-dtpa-bis(cytosine) at 375nm in the concentration range of 0.50×10^-5mol∙L^-1-5.00×10^-5mol∙L^-1 of Eu³⁺ ion display a better linear relationship. The limit of detection (LOD) was determined as 8.65×10^-7mol∙L^-1 and the corresponding correlation coefficient (R²) of the linear equation is 0.9807. It is wished that the proposed method could be applied for sensitively and selectively detecting Eu³⁺ ion.

Spectroscopic studies on interaction of BSA and Eu(III) complexes with H5ph-dtpa and H5dtpa ligands

An novel aromatic aminopolycarboxylic acid ligand, N-(2-N,N-Dicarboxymethylaminophenyl) ethylenediamine-N,N',N'-triacetic acid (H5ph-dtpa), was synthesized by improving experimental method and its corresponding Eu(III) complex, Na2[EuIII(ph-dtpa)(H2O)]·6H2O, was successfully prepared through heat-refluxing method. As a comparison, the Eu(III) complex with diethylenetriamine-N,N,N',N',N″-pentaacetic acid (H5dtpa) ligand, Na2[Eu(III)(dtpa)(H2O)]·6H2O, was also prepared by the same method. And then, the interaction between prepared Eu(III) complexes ([EuIII(dtpa)(H2O)]2- and [EuIII(ph-dtpa)(H2O)]2-) and bovine serum albumin (BSA) in aqueous solution were studied by the combination of ultraviolet-visible (UV-vis), fluorescence and circular dichroism (CD) spectroscopies. In addition, the binding sites of Eu(III) complexes ([EuIII(dtpa)(H2O)]2- and [EuIII(ph-dtpa)(H2O)]2-) to BSA molecules were also estimated by synchronous fluorescence. Moreover, the theoretical and experimental results show that the Van der Waals, hydrogen bond and π-π stacking interactions are the mainly impulse to the reaction. The binding distances (r) between Eu(III) complexes ([EuIII(dtpa)(H2O)]2- and [EuIII(ph-dtpa)(H2O)]2-) and BSA were obtained according to Förster's non-radiative energy transfer theory. Also, the determined UV-vis absorption spectroscopy, synchronous fluorescence and circular dichroism (CD) spectra showed that the conformation of BSA could be changed in the presence of Eu(III) complexes. The obtained results can help understand the action mode between rare earth metal complexes of aminopolycarboxylic acid ligands with BSA and they are also expected to provide important information of designs of new inspired drugs.

Molecular insights into the selective action of a magnetically removable complexone-grafted adsorbent

The IDA–RE³⁺ complexation of RE³⁺ on the surface of a hybrid silica adsorbent occurs under neutral or weakly acidic conditions apparently not via chelation but via the concerted action of the negatively charged carboxylate oxygen atoms, opening the possibility for enhanced selectivity.