Cation−Cation Interactions in Neptunyl(V) Compounds:  Hydrothermal Preparation and Structural Characterization of NpO2(IO3) and α- and β-AgNpO2(SeO3)

Albrecht‐Schmitt, Thomas E.; Almond, Philip M.; Sykora, Richard E.

doi:10.1021/ic034124z

Cited by 84 publications

(68 citation statements)

References 50 publications

(69 reference statements)

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“…[5][6][7][8][9][10][11][12][13][14][15][16] The CCI occurs through coordination of one actinide metal center by the oxo atom of a second actinyl unit. It can lead to the formation of dimers, [4][5][6][7][8] oligomers, [9][10][11] one-dimensional chains, [12][13][14] and multi-dimensional networks [15,16] that do not necessarily require the support of ancillary ligands. The CCIs are particularly well recognized for An V (An = U, Np and Pu) [4-6, 10, 12, 17-20] and have recently been identified in U VI chemistry.…”

Section: Introductionmentioning

confidence: 99%

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

Pan

Shamov

Schreckenbach

2010

Chemistry A European J

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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.

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Section: Introductionmentioning

confidence: 99%

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

Pan

Shamov

Schreckenbach

2010

Chemistry A European J

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“…Although the valence bond is 5+ from the chemical formula, the β-AgNpO 2 (SeO 3 ) is brown in color which might suggests the existence of a finite concentration of Np(IV) (i.e. Kramers ion) [6]. We think that the minority concentration of Np(IV) is responsible for the ESR signal, since Np(V) is to a large extent ESR silent.…”

Section: Methodsmentioning

confidence: 91%

“…Single crystals of β-AgNpO 2 (SeO 3 ) were prepared by methods previously described [6]. The crystals are dark in appearance, and were ~6.6×10 - Interference Device (SQUID) magnetometer over the temperature range 2 -200 K, and hysteresis measurements were carried out in the field range -2 T to 2 T. Due to the small size of the samples, the crystals were attached to the surface of a thin quartz pipe with GE varnish.…”

Section: Methodsmentioning

confidence: 99%

“…Since the Np atoms (i.e J=4 for Np(V) and J= 9/2 for Np(IV)) have the largest magnetic moment in this material, it is clear that this ESR is due to the Np 5f electrons. Although there are two Np sites per unit cell [6], only a single broad absorption line is observed. This suggests a non-negligible exchange interaction between the two Np sites [17], which is consistent with the magnetic ordering observed in the magnetization measurements.…”

Section: Methodsmentioning

confidence: 99%

“…The study of new compounds containing actinides, especially Neptunium (Np), has been an active area of research for many years [1][2][3][4][5][6][7][8][9][10]. The physical properties, and in particular the magnetic properties, are of interest since they depend significantly on the material surrounding the Np site: for instance Np(NpO 2 ) 2 (SeO 3 ) 3 [3], NpO 2 [12], but the interpretation is quite different, since the transitions have been reported to be metamagnetic and ferromagnetic in the two materials, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Magnetism and electron spin resonance in single crystalline β-AgNpO2(SeO3)

Jobiliong

Oshima

Brooks

et al. 2004

Solid State Communications

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We report magnetization, susceptibility, electrical transport, and electron spin resonance (ESR) studies of single crystals of β-AgNpO 2 (SeO 3 ). Here the valence of the Np sites is expected to be Np(V). We observe a magnetic transition below 8 K, where the transition temperature is dependent on the effective magnetic moment. Although the transition appears to be ferromagnetic, no hysteresis is seen in the magnetization, and the saturation moment above 0.1 T is found to be about 60% of the free NpO 2 ion moment. The decrease in the Np moments determined experimentally is thought to arise from crystal field and spin-orbit effects. Although Np(V) is expected to be ESR silent, we observe temperature dependent ESR spectra at ~44 GHz (for fields above the saturation field) that show slight shifts in the g-factor and line width at low temperatures. Our results provide evidence that both Np(V) and Np(IV) valences are present, where the latter may be a minority population. The crystals, although dark in appearance, are electrically insulating (ρ > 10 10 Ohm-cm) at room temperature.Moreover, the 5f electron systems have a greater exposure to their chemical environments than do the 4f electron systems, and hence the crystal field effect plays a significant role with the spinorbit coupling. Thus, it is necessary to consider the crystal structure, spin-orbit coupling, and crystal-field splitting in order to fully understand the magnetic properties of these compounds.

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Actinides: Crystallography

Scott

Cary

Cross

2018

Encyclopedia of Inorganic and Bioinorganic Chemistry

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Single crystal and powder X‐ray diffraction techniques helped define the actinide series during its genesis in the early twentieth century, and these are still helping forge new understanding in all actinides and especially the late actinides. The structural information provided by these techniques, including the three‐dimensional structures of molecules and associated bond distances and angles, have laid the foundation for understanding chemical reactivity and properties in actinide materials. This article will give a brief overview of X‐ray diffraction and the types of information this technique provides. The early history of actinide crystallography and the role it played in the development of the actinide series will be addressed. The common actinide isotopes used for crystallography will be described in terms of availability and hazards. An overview of important X‐ray structures (Th–Cf) that helped advance actinide science, including the discovery of new valence states, chemical bonds, periodic trends, covalency, and other important phenomena, will be given. The article will close with potential pitfalls and corresponding solutions relevant to practicing actinide crystallography, addressing absorption, heavy atoms and pseudosymmetry, hydrogen atom location and refinement, and safe containment of radioisotopes.

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Cation−Cation Interactions in Neptunyl(V) Compounds: Hydrothermal Preparation and Structural Characterization of NpO₂(IO₃) and α- and β-AgNpO₂(SeO₃)

Cited by 84 publications

References 50 publications

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

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

Magnetism and electron spin resonance in single crystalline β-AgNpO2(SeO3)

Actinides: Crystallography

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