Actinide structural studies. 15. Two 1,10-phenanthroline complexes of uranium(VI)

Engaging the nominally terminal oxo atoms of the linear uranyl (UO ) cation in non-covalent interactions represents both a significant challenge and opportunity within the field of actinide hybrid materials. An approach has been developed for promoting oxo atom participation in a range of non-covalent interactions, through judicious choice of electron donating equatorial ligands and appropriately polarizable halogen-donor atoms. As such, a family of uranyl hybrid materials was generated based on a combination of 2,5-dihalobenzoic acid and aromatic, chelating N-donor ligands. Delineation of criteria for oxo participation in halogen bonding interactions has been achieved by preparing materials containing 2,5-dichloro- (25diClBA) and 2,5-dibromobenzoic acid (25diBrBA) coupled with 2,2'-bipyridine (bipy) (1 and 2), 1,10-phenanthroline (phen) (3-5), 2,2':6',2''-terpyridine (terpy) (6-8), or 4'-chloro-2,2':6',2''-terpyridine (Cl-terpy) (9-10), which have been characterized through single crystal X-ray diffraction, Raman, Infrared (IR), and luminescence spectroscopy, as well as through density functional calculations of electrostatic potentials. Looking comprehensively, these results are compared with recently published analogues featuring 2,5-diiodobenzoic acid which indicate that although inclusion of a capping ligand in the uranyl first coordination sphere is important, it is the polarizability of the selected halogen atom that ultimately drives halogen bonding interactions with the uranyl oxo atoms.

Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Engaging the Terminal: Promoting Halogen Bonding Interactions with Uranyl Oxo Atoms

Carter

Kalaj

Surbella

et al. 2017

“…Figure 3 shows a view of the complex and selected bond lengths and angles are presented in Table 4. The structure is identical to that adopted by the BIPY and 1,10‐phenanthroline (PHEN) analogues,51, 52 with no significant difference in the corresponding UO and UN distances. The angle (23.74(10)°) between the plane of the BPM ligand and the mean equatorial plane of the complex is also identical to that observed in the BIPY compound.…”

Section: Resultsmentioning

confidence: 70%

2,2′‐Bipyrimidine as Efficient Sensitizer of the Solid‐State Luminescence of Lanthanide and Uranyl Ions from Visible to Near‐Infrared

Zucchi

Maury

Thuéry

et al. 2009

Treatment of Ln(NO(3))(3)nH(2)O with 1 or 2 equiv 2,2'-bipyrimidine (BPM) in dry THF readily afforded the monometallic complexes [Ln(NO(3))(3)(bpm)(2)] (Ln=Eu, Gd, Dy, Tm) or [Ln(NO(3))(3)(bpm)(2)]THF (Ln=Eu, Tb, Er, Yb) after recrystallization from MeOH or THF, respectively. Reactions with nitrate salts of the larger lanthanide ions (Ln=Ce, Nd, Sm) yielded one of two distinct monometallic complexes, depending on the recrystallization solvent: [Ln(NO(3))(3)(bpm)(2)]THF (Ln=Nd, Sm) from THF, or [Ln(NO(3))(3)(bpm)(MeOH)(2)]MeOH (Ln=Ce, Nd, Sm) from MeOH. Treatment of UO(2)(NO(3))(2)6H(2)O with 1 equiv BPM in THF afforded the monoadduct [UO(2)(NO(3))(2)(bpm)] after recrystallization from MeOH. The complexes were characterized by their crystal structure. Solid-state luminescence measurements on these monometallic complexes showed that BPM is an efficient sensitizer of the luminescence of both the lanthanide and the uranyl ions emitting visible light, as well as of the Yb(III) ion emitting in the near-IR. For Tb, Dy, Eu, and Yb complexes, energy transfer was quite efficient, resulting in quantum yields of 80.0, 5.1, 70.0, and 0.8 %, respectively. All these complexes in the solid state were stable in air.

“…For the complexes reported in the experiments, a parallel structure of two uranyl ions connected by oxygen bridges in polynuclear complexes is the most common. [8,14,15,30,33,[83][84][85] Recently, two T-shaped tetrameric cation-cation complexes with pentavalent [10] and hexavalent [11] uranyls have been reported. Additionally, there are some uranyl metallates with the combined Tshaped and parallel polyuranyl structures found in solidstate chemistry, [13,16] which usually exhibit one-to three-dimensional arrangements.…”

Section: Resultsmentioning

confidence: 99%

Binuclear Uranium(VI) Complexes with a “Pacman” Expanded Porphyrin: Computational Evidence for Highly Unusual Bis‐Actinyl Structures

Pan

Shamov

Schreckenbach

2010

On the basis of uranyl complexes reacting with a polypyrrolic ligand (H(4)L), we explored structures and reaction energies of a series of new binuclear uranium(VI) complexes using relativistic density functional theory. Full geometry optimizations on [(UO(2))(2)(L)], in which two uranyl groups were initially placed into the pacman ligand cavity, led to two minimum-energy structures. These complexes with cation-cation interactions (CCI) exhibit unusual coordination modes of uranyls: one is a T-shaped (T) skeleton formed by two linear uranyls {O(exo)=U(2)=O(endo)-->U(1)(=O(exo))(2)}, and another is a butterfly-like (B) unit with one linear uranyl coordinating side-by-side to a second cis-uranyl. The CCI in T was confirmed by the calculated longest distance and lowest stretching vibrational frequency of U(2)=O(endo) among the four U=O bonds. Isomer B is more stable than T, for which experimental tetrameric analogues are known. The formation of B and T complexes from the mononuclear [(UO(2))(H(2)L)(thf)] (M) was found to be endothermic. The further protonation and dehydration of B and T are thermodynamically favorable. As a possible product, we have found a trianglelike binuclear uranium(VI) complex having a O=U=O=U=O unit.