Synthesis and crystal structures of two new uranyl coordination compounds obtained in aqueous solutions of 1-butyl-2,3-dimethylimidazolium chloride

<p>Two new uranyl coordination compounds, [C₉H₁₇N₂]₃[(UO₂)₂(CrO₄)₂Cl₂(H₂O)₂]Cl·5H₂O (<b>1</b>) and (C₉H₁₇N₂)[(UO₂)(C₂O₄)Cl] (<b>2</b>), have been synthesized by adding potassium dichromate (K₂Cr₂O₇) or oxalic acid dihydrate (H₂C₂O₄·2H₂O) solution into an aqueous solution of uranyl nitrate and 1-butyl-2,3-dimethylimidazolium chloride [Bmmim]Cl. [Bmmim]Cl provides the charge balance and Cl ions that coordinate with uranyl ions. The fundamental building units of <b>1</b> and <b>2</b> are UO₆Cl pentagonal bipyramidal structures. Compound <b>1</b> exhibits a graphene-like structure with a system molar ratio of 1:1 for U:Cr and crystallizes in the orthorhombic space group Pbca, with <i>a</i> = 25.644(3) Å, <i>b</i> = 12.996(14) Å and <i>c</i> = 29.198(4) Å. 16-Membered rings are formed by CrO₄²⁻ and UO₂²⁺ in the crystal structure of <b>1</b>. Compound <b>2</b> crystallizes in monoclinic space group P2₁/n, with <i>a</i> = 10.759(3) Å, <i>b</i> = 11.395(3) Å, <i>c</i> = 14.149(4) Å, <i>β</i> = 102.962(9)° and shows one-dimensional (1D) serrated chains. Within the crystal structures of <b>1</b> and <b>2</b>, C–H_[Bmmim]Cl⋯O hydrogen bonds are identified. O–H_water⋯Cl hydrogen bonds are also detected in the crystal structure for <b>1</b>.</p

Different Interaction Mechanisms of Eu(III) and ²⁴³Am(III) with Carbon Nanotubes Studied by Batch, Spectroscopy Technique and Theoretical Calculation

Herein the sorption of Eu­(III) and ²⁴³Am­(III) on multiwalled carbon nanotubes (CNTs) are studied, and the results show that Eu­(III) and ²⁴³Am­(III) could form strong inner-sphere surface complexes on CNT surfaces. However, the sorption of Eu­(III) on CNTs is stronger than that of ²⁴³Am­(III) on CNTs, suggesting the difference in the interaction mechanisms or properties of Eu­(III) and ²⁴³Am­(III) with CNTs, which is quite different from the results of Eu­(III) and ²⁴³Am­(III) interaction on natural clay minerals and oxides. On the basis of the results of density functional theory calculations, the binding energies of Eu­(III) on CNTs are much higher than those of ²⁴³Am­(III) on CNTs, indicating that Eu­(III) could form stronger complexes with the oxygen-containing functional groups of CNTs than ²⁴³Am­(III), which is in good agreement with the experimental results of higher sorption capacity of CNTs for Eu­(III). The oxygen-containing functional groups contribute significantly to the uptake of Eu­(III) and ²⁴³Am­(III), and the binding affinity increases in the order of <i>S</i><i>OH</i> < <i>S</i><i>COOH</i> < <i>S</i><i>COO</i>^–. This paper highlights the interaction mechanism of Eu­(III) and ²⁴³Am­(III) with different oxygen-containing functional groups of CNTs, which plays an important role for the potential application of CNTs in the preconcentration, removal, and separation of trivalent lanthanides and actinides in environmental pollution cleanup

Two-Dimensional Inorganic Cationic Network of Thorium Iodate Chloride with Unique Halogen–Halogen Bonds

A unique two-dimensional inorganic cationic network with the formula [Th₃O₂(IO₃)₅(OH)₂]Cl was synthesized hydrothermally. Its crystal structure can best be described as positively charged slabs built with hexanuclear thorium clusters connected by iodate trigonal pyramids. Additional chloride anions are present in the interlayer spaces but surprisingly are not exchangeable, as demonstrated by a series of CrO₄^2– uptake experiments. This is because all chloride anions are trapped by multiple strong halogen–halogen interactions with short Cl–I bond lengths ranging from 3.134 to 3.333 Å, forming a special Cl-centered trigonal-pyramidal polyhedron as a newly observed coordination mode for halogen bonds. Density functional theory calculations clarified that electrons transformed from central Cl atoms to I atoms, generating a halogen–halogen interaction energy with a value of about −8.3 kcal mol^–1 per Cl···I pair as well as providing a total value of −57.9 kcal mol^–1 among delocalized halogen–halogen bonds, which is a new record value reported for a single halogen atom. Additional hydrogen-bonding interaction is also present between Cl and OH, and the interaction energy is predicted to be −8.1 kcal mol^–1, confirming the strong total interaction to lock the interlayer Cl anions

Two-Dimensional Inorganic Cationic Network of Thorium Iodate Chloride with Unique Halogen–Halogen Bonds

A unique two-dimensional inorganic cationic network with the formula [Th₃O₂(IO₃)₅(OH)₂]Cl was synthesized hydrothermally. Its crystal structure can best be described as positively charged slabs built with hexanuclear thorium clusters connected by iodate trigonal pyramids. Additional chloride anions are present in the interlayer spaces but surprisingly are not exchangeable, as demonstrated by a series of CrO₄^2– uptake experiments. This is because all chloride anions are trapped by multiple strong halogen–halogen interactions with short Cl–I bond lengths ranging from 3.134 to 3.333 Å, forming a special Cl-centered trigonal-pyramidal polyhedron as a newly observed coordination mode for halogen bonds. Density functional theory calculations clarified that electrons transformed from central Cl atoms to I atoms, generating a halogen–halogen interaction energy with a value of about −8.3 kcal mol^–1 per Cl···I pair as well as providing a total value of −57.9 kcal mol^–1 among delocalized halogen–halogen bonds, which is a new record value reported for a single halogen atom. Additional hydrogen-bonding interaction is also present between Cl and OH, and the interaction energy is predicted to be −8.1 kcal mol^–1, confirming the strong total interaction to lock the interlayer Cl anions

Impact of Al₂O₃ on the Aggregation and Deposition of Graphene Oxide

To assess the environmental behavior and impact of graphene oxide (GO) on living organisms more accurately, the aggregation of GO and its deposition on Al₂O₃ particles were systematically investigated using batch experiments across a wide range of solution chemistries. The results indicated that the aggregation of GO and its deposition on Al₂O₃ depended on the solution pH and the types and concentrations of electrolytes. MgCl₂ and CaCl₂ destabilized GO because of their effective charge screening and neutralization, and the presence of NaH₂PO₄ and poly­(acrylic acid) (PAA) improved the stability of GO with the increase in pH values as a result of electrostatic interactions and steric repulsion. Specifically, the dissolution of Al₂O₃ contributed to GO aggregation at relatively low pH or high pH values. Results from this study provide critical information for predicting the fate of GO in aquatic-terrestrial transition zones, where aluminum (hydro)­oxides are present

New Insight into GO, Cadmium(II), Phosphate Interaction and Its Role in GO Colloidal Behavior

This study establishes the relationship between the graphene oxide (GO) colloidal behavior and the co-adsorption of Cd­(II) and phosphate (P­(V)) on GO. Results reveal that the interactions among GO, Cd­(II), and P­(V) exhibit a significant dependence on solution chemistry and addition sequences and that these interactions subsequently affect the GO colloidal behavior. The GO aggregation is pH-dependent at pH < 4.0 and depends apparently on the binding ability of Cd­(II) to GO at pH > 4.0. When the components were added simultaneously, the presence of P­(V) enhances the GO binding capacity toward Cd­(II), confirmed by theoretical calculation, resulting in the greater destabilizing influence of Cd­(II) + P­(V) on GO than Cd­(II) at pH 3.0–9.5, while the formation of Cd₃(PO₄)₂ precipitate leads to a lower destabilizing influence of Cd­(II) + P­(V) on GO than Cd­(II) at pH > 9.5. Both pH and addition sequence affect the destabilizing ability of Cd­(II) + P­(V). These new insights are expected to provide valuable information not only for the application of GO as a potential adsorbent in multicomponent systems for heavy metal ion and oxyanion co-removal but also for the fate and risk assessment of GO after serving as heavy metal ion and oxyanion carrier