Influence of Electronic Modulation of Phenanthroline-Derived Ligands on Separation of Lanthanides and Actinides

Abstract

The solvent extraction, complexing ability, and basicity of tetradentate N-donor 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4-BT- Phen) and its derivatives functionalized by Br, hydroxyphenyl, nitryl were discussed and compared. It was demonstrated that four BTPhen ligands are able to selectively extract Am(lll) over Eu(lll). It was notable that the distribution ratio of 5-nitryl-CyMe4-BTPhen for Eu(lll) was suppressed under 0.02, which was much lower compared to DEu(lll) = 1 by CyMe4-BTPhen. The analysis of the effect of the substituent on the affinity to lanthanides was conducted by UV/vis and fluorescence spectroscopic titration. The stability constants of various ligands with Eu(lll) were obtained by fitting titration curve. Additionally, the basicity of various ligands was determined to be 3.1 ± 0.1, 2.3 ± 0.2, 0.9 ± 0.2, 0.5 ± 0.1 by NMR in the media of CD3OD with the addition of DClO4. The basicity of ligands follows the order of L1 > L2 > L3 > L4, indicating the tendency of protonation decreases with the electron-withdrawing ability increase.

Periodic Trends in the Stabilization of Actinyls in Their Higher Oxidation States Using Pyrrophen Ligands

“…This coordination property distinguishes the actinyls from other f-block elements (i.e., lanthanide ions, Ln 3+ ) that exhibit higher coordination numbers in their most common trivalent state. 6,7 The pentavalent actinyl cations [AnO 2 ] + were identified in acidic solutions more commonly than heptavalent actinyl cations [AnO 2 ] 3+ , while the relatively stable hexavalent actinyl cations [AnO 2 ] 2+ are prevalent over a wide pH range. 8−10 Uranyl(V) compounds have been demonstrated to be stable in nature.…”

“…These positively charged moieties show characteristic low coordination, i.e., with penta- or hexadentate ligand environments , in the equatorial plane in their higher oxidation states (V/VI/VII). This coordination property distinguishes the actinyls from other f-block elements (i.e., lanthanide ions, Ln 3+ ) that exhibit higher coordination numbers in their most common trivalent state. , The pentavalent actinyl cations [AnO 2 ] + were identified in acidic solutions more commonly than heptavalent actinyl cations [AnO 2 ] 3+ , while the relatively stable hexavalent actinyl cations [AnO 2 ] 2+ are prevalent over a wide pH range. − Uranyl­(V) compounds have been demonstrated to be stable in nature. − Although the hexavalent neptunyl and plutonyl have been stabilized in the aqueous medium, the oxidation of heavier f-elements, such as Am­(V) to Am­(VI), is challenging. Tetraoxo actinides (of Np, Pu, and Am) were studied computationally for the periodic properties they exhibit in the heptavalent OS, in which heptavalent Np and Pu ions were stabilized as [AnO 4 (OH) 2 ] 3– , while heptavalent Am was not identified in a bonded state .…”

The study of a novel high selectivity pyrenyl-based fluorescence probe with aggregation-induced emission characteristics for Fe3+ detection designed by a structure modulation strategy

“…In stark contrast to pypyr-CH 3 , pypyr-CF 3 is hardly affected over a wide pH range of 2–13. The conspicuous difference between pypyr-CF 3 and pypyr-CH 3 in acidic solution may be because trifluoromethyl weakens the protonation of pypyr due to the strong electron-withdrawing effect, 54 which gives pypyr-CF 3 a greater opportunity to interact with Fe 3+ in acidic environments. After the addition of Fe 3+ , the fluorescence intensity of pypyr-CF 3 was quenched and fluctuated reasonably over the pH range of 2–11.…”

Efficient Extraction in High-Acidity HNO3 Solution for Selective Separation of Am3+ Over Eu3+ by Amine-Diamide Ligands

“…With the rapid development of nuclear energy, more and more spent fuel is produced, which has constituted great threat to the environment and human health due to its strong radioactivity and high toxicity. − Although the major actinides (U and Pu) can be recovered by means of the PUREX (Plutonium Uranium Reduction EXtraction) process, , the high-level liquid waste (HLLW) issued from this process is still highly radioactive and toxic and has to be further treated. , Therein lie appreciable amounts of long-lived minor actinides (Ans; Am, C m, etc.) which are the main contributors to the long-term radiotoxicity of HLLW. , This has necessitated seeking methods for separating these minor Ans from HLLW.…”