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A single-source-precursor approach was developed to synthesize uranium-based materials outside of the typically-studied oxides. This approach allows for shorter reaction times, milder reaction conditions, and control over the chemicals present in synthesis. To this end, the first homoleptic uranium thioamidate complex was synthesized as a precursor for US2 materials. Pyrolysis of the thioamidate results in decomposition via an alkene elimination pathway and formation of γ-US2, which has historically been hard to access without the need for a secondary sulfur source. Despite the oxophilicity of uranium, the method successfully forms US2 without the inclusion of oxygen in the bulk final product. These findings are supported by simultaneous thermal analysis, elemental analysis, powder X-ray diffraction, and uranium L3-edge X-ray absorption fine-structure spectroscopy. This work represents the first example of a single-source precursor approach to target and synthesize actinide materials other than the oxides.

Traditional models of lanthanide electronic structure suggest that bonding is predominantly ionic, and that covalent orbital mixing is not an important factor in determining magnetic properties. Here, 4f orbital mixing and its impact on the magnetic susceptibility of Cp'3Eu (Cp' = C5H4SiMe3) was analyzed experimentally using magnetometry and X-ray absorption spectroscopy (XAS) methods at the C K-, Eu M5,4-, and L3-edges. Pre-edge features in the experimental and TDDFT-calculated C K-edge XAS spectra provided unequivocal evidence of C 2p and Eu 4f orbital mixing in the π-antibonding orbital of a' symmetry. The charge-transfer configurations resulting from 4f orbital mixing were identified spectroscopically by using Eu M5,4-edge and L3-edge XAS. Modeling of variable-temperature magnetic susceptibility data showed excellent agreement with the XAS results and indicated that increased magnetic susceptibility of Cp'3Eu is due to removal of the degeneracy of the 7F1 excited state due to mixing between the ligand and Eu 4f orbitals.

Ligand K-edge X-ray absorption spectroscopy (XAS) is regularly used to determine the ligand contribution to metal-ligand bonds. For quantitative studies, the pre-edge transition intensities must be referenced to an intensity standard, and pre-edge intensities obtained from different ligand atoms cannot be compared without standardization due to different cross sections at each absorption edge. In this work, the intensities of the 1s → σ* transitions in F2, Cl2, and Br2 are analyzed for their use as references for ligand K-edge XAS. We show that the intensities of these transitions are equal to the intensities of the 1s → np transitions in the unbound halogens. This finding is supported by a comparison between the normalized experimental intensities for the molecules and the calculated oscillator strengths for the atoms. These results highlight the potential for these molecules to be used as intensity standards in F, Cl, and Br K-edge XAS experiments.

The actinide elements are attractive alternatives to transition metals or lanthanides for the design of exchange-coupled multinuclear single-molecule magnets. However, the synthesis of such compounds is challenging, as is unraveling any contributions from exchange coupling to the overall magnetism. To date, only a few actinide compounds have been shown to exhibit exchange coupling and single-molecule magnetism. Here, we report triangular uranium(III) clusters of the type (CpiPr5)3U3X (1-X; X = Cl, Br, I; CpiPr5 = pentaisopropylcyclopentadienyl), which are synthesized via reaction of the aryloxide-bridged precursor (CpiPr5)2U2(OPhtBu)4 with excess Me3SiX. Spectroscopic analysis suggests the presence of covalency in the uranium-halide interactions arising from 5f orbital participation in bonding. The dc magnetic susceptibility data reveal the presence of antiferromagnetic exchange coupling between the uranium(III) centers in these compounds, with the strength of the exchange decreasing down the halide series. Ac magnetic susceptibility data further reveal all compounds to exhibit slow magnetic relaxation under zero dc field. In 1-I, which exhibits particularly weak exchange, magnetic relaxation occurs via a Raman mechanism associated with the individual uranium(III) centers. In contrast, for 1-Br and 1-Cl, magnetic relaxation occurs via an Orbach mechanism, likely involving relaxation between ground and excited exchange-coupled states. Significantly, in the case of 1-Cl, magnetic relaxation is sufficiently slow such that open magnetic hysteresis is observed up to 2.75 K, and the compound exhibits a 100-s blocking temperature of 2.4 K. This compound provides the first example of magnetic blocking in a compound containing only actinide-based ions, as well as the first example involving the uranium(III) oxidation state.

Vacancy ordered double perovskites Cs2Te(IV)X6 have been found to exhibit molecule-like electronic behavior when X is Cl- or Br- due to the zero-dimensional (0D) nature of their octahedral units. Electronically isolated building blocks, the [TeBr6]2- ionic octahedron, serve as the fundamental electronic unit of the Cs2TeBr6 solid. Herein, a detailed understanding of the Cs2TeBr6 electronic structure and its photoexcitation is presented with consideration of individual molecular orbitals from these isolated octahedral building blocks. Two optical absorption features correspond to two unique electronic transitions, (1) a highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) transition under 455 nm excitation and (2) mixed transitions including lower HOMO states to LUMO transition and HOMO to higher LUMO states transition under 365 nm excitation. With this in mind, we examined the excitation wavelength-dependent photo-oxidation of benzyl alcohol using Cs2TeBr6 as the photocatalyst. Significant differences in photocatalytic performance were observed, and different forms of activated alcohol radicals were detected under the two excitation wavelengths. As a case study, this work highlights the application of molecule-like halide perovskites in photocatalysis. The highly tunable energy band structures and catalytic centers in perovskites can offer a valuable platform for photocatalytic mechanistic studies and catalyst development in the foreseeable future.

PURPOSE: Older adults (age ≥ 65 years) are the fastest growing age group undergoing lung transplantation. Further, international consensus document for the selection of lung transplant candidates no longer suggest a fixed upper age limit. Although carefully selected older adults can derive great benefit, understanding which older adults will do well after transplant with improved survival and health-related qualiy of life is key to informed decision-making. Herein, we review the epidemiology of aging in lung transplantation and its impact on outcomes, highlight selected physiological measures that may be informative when evaluating and managing older lung transplant patients, and identify directions for future research. RECENT FINDINGS: In general, listing and transplanting older, sicker patients has contributed to worse clinical outcomes and greater healthcare use. Emerging evidence suggest that measures of physiological age, such as frailty, body composition, and neurocognitive and psychosocial function, may better identify risk for poor transplant outcomes than chronlogical age. SUMMARY: The evidence base to inform transplant decision-making and improvements in care for older adults is small but growing. Multipronged efforts at the intersection of aging and lung transplantation are needed to improve the clinical and patient centered outcomes for this large and growing cohort of patients. Future research should focus on identifying novel and ideally modifiable risk factors for poor outcomes specific to older adults, better approaches to measuring physiological aging (e.g., frailty, body composition, neurocognitive and psychosocial function), and the underlying mechanisms of physiological aging. Finally, interventions that can improve clinical and patient centered outcomes for older adults are needed.