The speciation of protactinium since its discovery: a nightmare or a path of resilience

This review concerns the speciation of protactinium in aqueous solution under its both oxidation states +IV and +V. Emphasis is placed on experimental data obtained at trace level but also in macroscopic amount leading to the determination of thermodynamic and structural data. Thus, the complexation of Pa(V) with mineral acids and organic acids, mainly polyaminocarboxylic acids (iminodiacetic acid [IDA], nitrilotriacetic acid [NTA], ethylenediaminetetraacetic acid [EDTA] and diethylenetriaminepentaacetic acid [DTPA]) are highlighted and compared. The review also includes the actual knowledge about the Pa(IV) aqueous chemistry pinpointing its spectroscopic features.

Density functional theory investigations on the coordination of Pa(v) with N,N-dialkylamide

The density functional theory (DFT) method was used to study the coordination of a series of N,N-dialkylamides with Pa(v) to shed light on the inherent principles for screening amide extractants of Pa(v) from aqueous solution.

Protactinium(V) in aqueous solution: a light actinide without actinyl moiety

This review highlights recent data on the complexation of Pa(V) with inorganic (fluoride and sulphate) and organic (oxalate, nitrilotriacetate, diethylenetriaminepentaacetate) ligands in solution. New thermodynamic parameters relative to the complexation of Pa(V) with sulphate are presented. The review also includes gas phase and theoretical studies focused on the interaction of Pa(V) in the dioxo and oxo forms with water.

Density Functional Theory Investigations on the Mechanism of Formation of Pa(V) Ion in Hydrous Solutions

Due to the enormous threat of protactinium to the environment and human health, its disposal and chemistry have long been important topics in nuclear science. [PaO(H₂O)₆]3+ is proposed as the predominant species in hydrous and acidic solutions, but little is known about its formation mechanism. In this study, density functional theory (DFT) calculations demonstrate a water coordination-proton transfer-water dissociation mechanism for the formation of PaO3+ in hydrous solutions. First, Pa(V) ion preferentially forms hydrated complexes with a coordination number of 10. Through hydrogen bonding, water molecules in the second coordination sphere easily capture two protons on the same coordinated H₂O ligand to form [PaO(H₂O)₉]3+. Water dissociation then occurs to generate the final [PaO(H₂O)₆]3+, which is the thermodynamic product of Pa(V) in hydrous solutions.

Iron molybdenum nitrilotriacetate and iminodiacetate – spectroscopy, structural characterization and CO2 adsorption

The tetranuclear iron molybdate Na₆[(MoO₂)₂O₂Fe₂(nta)₄]·16H₂O (1) and its isomorphous complexes form 2D water layer structures in a modular manner, and a decanuclear heterometallic polymer, [(MoO₄)₂FeII4FeIII4(ida)₈]_n (2), contains an interesting cubic 3D microporous structure with a 3.3 Å diameter hole and can adsorb a small amount of CO₂.