Structural and computational characterization of a bridging zwitterionic-amidoxime uranyl complex

Abstract

A bridging (μ2) neutral zwitterionic amidoxime binding mode previously unobserved between amidoximes and uranyl is reported and compared to other uranyl amidoxime complexes.

Influencing prototropy by metal ion coordination: supramolecular transformation of a dynamer into a Zn-based toroidal species

“…Similar cases of metal ion binding leading to displacement of a tautomeric equilibrium have been seen in uranyl ion complexes of amidoximes, where the ligand is bound in its neutral but zwitterionic form obtained by proton transfer from O to oxime-N. 19,20 Somewhat surprisingly therefore, these principles have not been explored for more complex dynamic aggregates in solution and in two dimensions on a flat surface, even though structurally distinct supramolecular assemblies can be efficiently studied in submolecular detail with scanning probe techniques. 21,22 In seeking to explore enhancement of metal ion effects on a tautomeric equilibrium, we have examined the coordination behavior of the 2-pyridone-derived ligand H 2 L ( Fig.…”

Electronic Structures and Unusual Chemical Bonding in Actinyl Peroxide Dimers [An2O6]2+ and [(An2O6)(12-crown-4 ether)2]2+ (An = U, Np, and Pu)

“…The O b –O b bond is broken, due to the long distance (2.468 Å), and meanwhile the U–U and U–O b distances are significantly shortened to 3.389 and 2.096 Å, respectively. This situation is commonly observed in uranyl polymeric complexes, such as the dihydroxyl binding to uranyl in K 12 [(UO 2 ) 6 (O 2 ) 9 (OH) 6 ]· x H 2 O complexes, , and the diamidoximo binding to uranyl in (UO 2 ) 2 (NO 3 ) 4 (μ 2 -benzyl-amidoxime) 2 ·H 2 O, which provides further linkers for the polymeric formation. In the third isomer, two bridged O b atoms form a superoxide moiety with an O b –O b bond length of 1.309 Å; thus, the distance of U–O b increases to 2.508 Å, implying weak interaction between uranyl and the 2 O 2 1– unit.…”

Uranyl Speciation on the Surface of Amidoximated Polyacrylonitrile Mats

“…The first binding motif displays both acetamidoxime and benzamidoxime molecules with an η 1 -O binding through the oxygen atom in the oxime functional group . The second binding motif involves side-on η 2 binding through the N–O bond of the amidoxime functionality, which was shown to be the most stable binding by density functional theory. − A third binding motif was recently reported with the first dinuclear AO–uranyl complex, where the uranyl metal centers were bridged by two zwitterionic benzamidoxime molecules through the μ 2 -O atom of the oxime . While the reported AO–uranyl structures are good references for possible binding motifs, they are not representative of the AO–uranyl complexes on the surface of AO-PAN mat,s where there is a prevalence of hydrolysis effects and high amidoxime to uranyl molar ratios, causing considerable amounts of amorphous precipitation on the surface of the AO-PAN mat during uranyl uptake experiments.…”

“…33−36 A third binding motif was recently reported with the first dinuclear AO−uranyl complex, where the uranyl metal centers were bridged by two zwitterionic benzamidoxime molecules through the μ 2 -O atom of the oxime. 31 While the reported AO−uranyl structures are good references for possible binding motifs, they are not representative of the AO−uranyl complexes on the surface of AO-PAN mat,s where there is a prevalence of hydrolysis effects and high amidoxime to uranyl molar ratios, causing considerable amounts of amorphous precipitation on the surface of the AO-PAN mat during uranyl uptake experiments. The hydrolysis effects typically result in bridging μ 2 -OH or μ 3 -O ligands between uranyl metal centers, creating oligomeric species and promoting surface precipitation.…”

“…Identification of the AO–uranyl binding motifs and uranyl speciation on the AO-PAN mat surface requires a thorough elucidation of small-molecule AO–uranyl model complexes. , A total of three different binding motifs has been reported on the basis of experimental findings and deposited crystal structures, but a systematic understanding of the related spectral signals has not been provided in the literature. The first binding motif displays both acetamidoxime and benzamidoxime molecules with an η 1 -O binding through the oxygen atom in the oxime functional group .…”