How to Bend the Uranyl Cation via Crystal Engineering

Abstract

Bending the linear uranyl (UO) cation represents both a significant challenge and opportunity within the field of actinide hybrid materials. As part of related efforts to engage the nominally terminal oxo atoms of uranyl cation in noncovalent interactions, we synthesized a new uranyl complex, [UO(CHN)(CHClO)]·2HO (complex 2), that featured both deviations from equatorial planarity and uranyl linearity from simple hydrothermal conditions. Based on this complex, we developed an approach to probe the nature and origin of uranyl bending within a family of hybrid materials, which was done via the synthesis of complexes 1-3 that display significant deviations from equatorial planarity and uranyl linearity (O-U-O bond angles between 162° and 164°) featuring 2,4,6-trihalobenzoic acid ligands (where Hal = F, Cl, and Br) and 1,10-phenanthroline, along with nine additional "nonbent" hybrid materials that either coformed with the "bent" complexes (4-6) or were prepared as part of complementary efforts to understand the mechanism(s) of uranyl bending (7-12). Complexes were characterized via single crystal X-ray diffraction and Raman, infrared (IR), and luminescence spectroscopy, as well as via quantum chemical calculations and density-based quantum theory of atoms in molecules (QTAIM) analysis. Looking comprehensively, these results are compared with the small library of bent uranyl complexes in the literature, and herein we computationally demonstrate the origin of uranyl bending and delineate the energetics behind this process.

Actinyl-Modified g-C3N4 as CO2 Activation Materials for Chemical Conversion and Environmental Remedy via an Artificial Photosynthetic Route

“… In addition to these characteristic CN peaks, additional peaks in the range of 800–880 cm –1 are found in CN-An m complexes, which are assigned to AnO stretching vibrations. These are consistent with their experimentally reported values. , Moreover, the peak observed at 1604 cm –1 in CN shows a considerable shift in the actinyl complexes (1667 cm –1 ), caused by the An–N bonding. Furthermore, the C–N bond stretching could be observed at or around 1510 cm –1 in the CN-An m complexes.…”

“…These are consistent with their experimentally reported values. 79,84 Moreover, the peak observed at 1604 cm −1 in CN shows a considerable shift in the actinyl complexes (1667 cm −1 ), caused by the An−N bonding.…”

“…The small ρ(r) value with positive ∇ 2 ρ(r) value and 0.5 > −G(r)/V(r) < 1 of An−N suggests a dative interaction with some covalency. 79,80 The partially covalent interaction is able to enhance the catalytic performance of these CN-ligated actinyl complexes relative to CN.…”

Coordination of Uranyl to the Redox-Active Calix[4]pyrrole Ligand

“…For comparison, the uranyl pyridinophane complexes, [U VI O 2 (OTf) 2 ( H N4)] and [U VI O 2 (OTf)­(THF)­( Me N4)]­[OTf] ( H N4 = 2,11-diaza­[3,3]­(2,6) pyridinophane, and Me N4 = N , N ′-dimethyl-2,11-diaza­[3,3]­(2,6) pyridinophane) feature O–U–O angles of 162.8(3)° and 161.7(5)°, respectively . Similarly, the uranyl 1,10-phenanthroline (phen) complexes, [U VI O 2 (phen) 2 (2,4,6-X 3 C 6 H 2 CO 2 ) 2 ] (X = F, Cl, Br), feature O–U–O angles ranging from 164.9(2)° to 162.2(2)° . For further comparison, [NEt 4 ] 2 [U VI O 2 (η 5 -C 5 Me 5 )­(CN) 3 ] and (η 5 -C 5 Me 5 )­U VI O 2 ( Mes PDI Me ), which feature similar η 5 -bound rings, adopt O–U–O angles of 168.40(9)°, and 168.3(2)°, respectively.…”

Probing hydrogen and halogen-oxo interactions in uranyl coordination polymers: a combined crystallographic and computational study

“…Crystal engineering within actinide hybrid materials, in particular those incorporating hexavalent uranium, is an area of sustained interest as it has proven to be a route that allows for the rational preparation of materials with desired structures and properties. [1][2][3][4][5][6][7][8][9][10][11] This approach is predicated upon the directed assembly of tectons into crystalline architectures via attractive, noncovalent synthons, and utilization within uranyl hybrid materials has necessitated the development of a hierarchy of acceptordonor pairing preferences based on a detailed knowledge of the relationship between intra-and intermolecular interactions. 12 Recently, our group has been investigating the potential for crystal engineering to support engagement of the nominally terminal uranyl oxo groups, [13][14][15][16][17] and here we continue these efforts, employing hydrogen and halogen bonding for assembly and then describing uranyl oxo atom behavior as a synthon acceptor site.…”