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DOE OSTI2020

Materials Data on PrMgAg by Materials Project

MgPrAg crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Mg is bonded in a 4-coordinate geometry to four Ag atoms. There are two shorter (2.88 Å) and two longer (3.04 Å) Mg–Ag bond lengths. Pr is bonded in a 5-coordinate geometry to five Ag atoms. There are four shorter (3.21 Å) and one longer (3.25 Å) Pr–Ag bond lengths. There are two inequivalent Ag sites. In the first Ag site, Ag is bonded in a 9-coordinate geometry to six equivalent Mg and three equivalent Pr atoms. In the second Ag site, Ag is bonded in a 9-coordinate geometry to three equivalent Mg and six equivalent Pr atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on PrH18(BrO6)3 by Materials Project

Pr(H2O)9(BrO3)3 crystallizes in the hexagonal P6_3mc space group. The structure is zero-dimensional and consists of six hypobromous acid;dihydrate molecules and two Pr(H2O)9 clusters. In each Pr(H2O)9 cluster, Pr3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Pr–O bond distances ranging from 2.51–2.55 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to one Pr3+ and two equivalent H1+ atoms. In the second O2- site, O2- is bonded in a water-like geometry to one Pr3+ and two equivalent H1+ atoms. In the third O2- site, O2- is bonded in a water-like geometry to one Pr3+ and two equivalent H1+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on PrBi3 by Materials Project

PrBi3 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pr is bonded to twelve Bi atoms to form a mixture of corner, edge, and face-sharing PrBi12 cuboctahedra. There are four shorter (3.37 Å) and eight longer (3.65 Å) Pr–Bi bond lengths. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded in a 12-coordinate geometry to four equivalent Pr and four equivalent Bi atoms. All Bi–Bi bond lengths are 3.37 Å. In the second Bi site, Bi is bonded in a square co-planar geometry to four equivalent Pr atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on PrMoBrO4 by Materials Project

PrMoO4Br crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Pr3+ sites. In the first Pr3+ site, Pr3+ is bonded in a 8-coordinate geometry to five O2- and three Br1- atoms. There are a spread of Pr–O bond distances ranging from 2.43–2.69 Å. There are two shorter (3.02 Å) and one longer (3.03 Å) Pr–Br bond lengths. In the second Pr3+ site, Pr3+ is bonded in a 8-coordinate geometry to seven O2- and one Br1- atom. There are a spread of Pr–O bond distances ranging from 2.42–2.88 Å. The Pr–Br bond length is 3.08 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.78–1.83 Å. In the second Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.77–1.83 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pr3+, one Mo6+, and three equivalent Br1- atoms. There are a spread of O–Br bond distances ranging from 3.47–3.69 Å. In the second O2- site, O2- is bonded in a distorted linear geometry to one Pr3+, one Mo6+, and one Br1- atom. The O–Br bond length is 3.25 Å. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two Pr3+, one Mo6+, and two equivalent Br1- atoms. There are one shorter (3.45 Å) and one longer (3.54 Å) O–Br bond lengths. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two Pr3+, one Mo6+, and two equivalent Br1- atoms. There are one shorter (3.43 Å) and one longer (3.56 Å) O–Br bond lengths. In the fifth O2- site, O2- is bonded in a distorted linear geometry to one Pr3+, one Mo6+, and one Br1- atom. The O–Br bond length is 3.19 Å. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Pr3+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a distorted linear geometry to one Pr3+ and one Mo6+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Pr3+ and one Mo6+ atom. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a distorted water-like geometry to two equivalent Pr3+ atoms. In the second Br1- site, Br1- is bonded in a 2-coordinate geometry to two Pr3+ and nine O2- atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Toward particle-resolved accuracy in Euler–Lagrange simulations of multiphase flow using machine learning and pairwise interaction extended point-particle (PIEP) approximation

This study presents two different machine learning approaches for the modeling of hydrodynamic force on particles in a particle-laden multiphase flow. Results from particle-resolved direct numerical simulations (PR-DNS) of flow over a random array of stationary particles for eight combinations of particle Reynolds number (Re) and volume fraction (φ) are used in the development of the models. The first approach follows a two-step process. In the first flow prediction step, the perturbation flow due to a particle is obtained as an axisymmetric superposable wake using linear regression. In the second force prediction step, the force on a particle is evaluated in terms of the perturbation flow induced by all its neighbors using the generalized Faxén form of the force expression. In the second approach, the force data on all the particles from the PR-DNS simulations are used to develop an artificial neural network (ANN) model for direct prediction of force on a particle. Due to the unavoidable limitation on the number of fully resolved particles in the PR-DNS simulations, direct force prediction with the ANN model tends to over-fit the data and performs poorly in the prediction of test data. In contrast, due to the millions of grid points used in the PR-DNS simulations, accurate flow prediction is possible, which then allows accurate prediction of particle force. This hybridization of multiphase physics and machine learning is particularly important, since it blends the strength of each, and the resulting pairwise interaction extended point-particle model cannot be developed by either physics or machine learning alone.

42 ENGINEERING↗

DOE OSTI2019

Structural studies of antiviral inhibitor with HIV-1 protease bearing drug resistant substitutions of V32I, I47V and V82I

HIV-1 protease inhibitors are effective in HIV/AIDS therapy, although drug resistance is a severe problem. This study examines the effects of four investigational inhibitors against HIV-1 protease with drug resistant mutations of V32I, I47V and V82I (PR Tri ) that model the inhibitor-binding site of HIV-2 protease. These inhibitors contain diverse chemical modifications on the darunavir scaffold and form new interactions with wild type protease, however, the measured inhibition constants for PR Tri mutant range from 17 to 40 nM or significantly worse than picomolar values reported for wild type enzyme. The X-ray crystal structure of PR Tri mutant in complex with inhibitor 1 at 1.5 Å resolution shows minor changes in interactions with inhibitor compared with the corresponding wild type PR complex. Instead, the basic amine at P2 of inhibitor together with mutation V82I induces two alternate conformations for the side chain of Arg8 with new interactions with inhibitor and Leu10. Hence, inhibition is influenced by small coordinated changes in hydrophobic interactions.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2026

Cross-slip and easy-glide CRSS in titanium: Theoretical predictions and in-situ TEM measurements

This study investigates the mechanics of prismatic and first-order pyramidal $\langle$a$\rangle$ slip in titanium (Ti), elucidating the physics of easy-glide and cross-slip through a combination of theory and experiments. Screw-character prismatic (Pr) dislocations in Ti are of particular interest because their complex cores can be stable or unstable, leading to activation by either cross-slip or planar glide. To investigate these mechanisms, site-specific micro tensile samples were prepared using focused ion beam (FIB) milling and mounted on a push-to-pull (PTP) device for in-situ transmission electron microscopy (TEM) tensile testing. The in-situ experiments provide direct observations of the onset of dislocation motion and the precise determination of the critical resolved shear stress (CRSS) for the activated mechanisms, and its evolution with load cycling. A comprehensive theory has been developed to predict the CRSS values for easy glide, cross-slip, and multiplication of dislocations. Predicted critical stresses for pyramidal (π)-to-Pr and reverse cross-slip agree closely with the experimental measurements. The latter cross-slip stress is a factor of two higher than that of unobstructed planar slip. The model accounts for overlapping dislocation cores and employs a Wigner-Seitz based cell to evaluate misfit energies. By combining ab initio density functional theory (DFT) with anisotropic elasticity, the framework identifies minimum energy pathways for dislocation glide, which can be intermittent and zig-zag. A simplified expression utilizing (π) and Pr Schmid factor ratios is proposed for critical stress corresponding to (π)-to-Pr cross-slip transition. The results are strongly dependent on crystal orientation, underscoring non-Schmid behavior. Overall, this study explores key critical stress parameters essential for informing higher-scale simulations of plasticity in Ti.

Critical stress↗

DOE OSTI2014

Whole Lung Irradiation for Adults With Pulmonary Metastases From Ewing Sarcoma

Purpose: To evaluate feasibility and patterns of failure in adult patients with Ewing sarcoma (ES) treated with whole lung irradiation (WLI) for pulmonary metastases. Methods and Materials: Retrospective review of all ES patients treated at age 18 or older with 12-15 Gy WLI for pulmonary metastases at a single institution between 1990 and 2014. Twenty-six patients met the study criteria. Results: The median age at WLI was 23 years (range, 18-40). The median follow-up time of the surviving patients was 3.8 years (range, 1.0-9.6). The 3-year cumulative incidence of pulmonary relapse (PR) was 55%, with a 3-year cumulative incidence of PR as the site of first relapse of 42%. The 3-year event-free survival (EFS) and overall survival (OS) were 38 and 45%, respectively. Patients with exclusively pulmonary metastases had better outcomes than did those with extrapulmonary metastases: the 3-year PR was 45% in those with exclusively lung metastases versus 76% in those with extrapulmonary metastases (P=.01); the 3-year EFS was 49% versus 14% (P=.003); and the 3-year OS was 61% versus 13% (P=.009). Smoking status was a significant prognostic factor for EFS: the 3-year EFS was 61% in nonsmokers versus 11% in smokers (P=.04). Two patients experienced herpes zoster in the radiation field 6 and 12 weeks after radiation. No patients experienced pneumonitis or cardiac toxicity, and no significant acute or late sequelae were observed among the survivors. Conclusion: WLI in adult patients with ES and lung metastases is well tolerated and is associated with freedom from PR of 45% at 3 years. Given its acceptable toxicity and potential therapeutic effect, WLI for pulmonary metastases in ES should be considered for adults, as it is in pediatric patients. All patients should be advised to quit smoking before receiving WLI.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2014

Contrast-Enhanced Proton Radiography for Patient Set-up by Using X-Ray CT Prior Knowledge

Purpose: To obtain a contrasted image of the tumor region during the setup for proton therapy in lung patients, by using proton radiography and x-ray computed tomography (CT) prior knowledge. Methods and Materials: Six lung cancer patients' CT scans were preprocessed by masking out the gross tumor volume (GTV), and digitally reconstructed radiographs along the planned beam's eye view (BEV) were generated, for a total of 27 projections. Proton radiographies (PR) were also computed for the same BEV through Monte Carlo simulations. The digitally reconstructed radiograph was subtracted from the corresponding proton image, resulting in a contrast-enhanced proton radiography (CEPR). Michelson contrast analysis was performed both on PR and CEPR. The tumor region was then automatically segmented on CEPR and compared to the ground truth (GT) provided by physicians in terms of Dice coefficient, accuracy, precision, sensitivity, and specificity. Results: Contrast on CEPR was, on average, 4 times better than on PR. For 10 lateral projections (±45° off of 90° or 270°), although it was not possible to distinguish the tumor region in the PR, CEPR offers excellent GTV visibility. The median ± quartile values of Dice, precision, and accuracy indexes were 0.86 ± 0.03, 0.86 ± 0.06, and 0.88 ± 0.02, respectively, thus confirming the reliability of the method in highlighting tumor boundaries. Sensitivity and specificity analysis demonstrated that there is no systematic over- or underestimation of the tumor region. Identification of the tumor boundaries using CEPR resulted in a more accurate and precise definition of GTV compared to that obtained from pretreatment CT. Conclusions: In most proton centers, the current clinical protocol is to align the patient using kV imaging with bony anatomy as a reference. We demonstrated that CEPR can significantly improve tumor visualization, allowing better patient set-up and permitting image guided proton therapy (IGPT)

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2017

Exploiting the Reactivity of Actinide Fluoride Bonds for the Synthesis of a New Class of Bis(azide) Uranium Complexes

The terminal actinide fluoride bonds in (C 5 Me 5 ) 2 ThF 2 (py) (py = pyridine) and (C 5 Me 5 ) 2 UF 2 (O=PR 3 ) (R = Me, Ph) react with two equivalents of Me 3 SiN 3 in toluene to form the polymeric thorium bis(azide), [(C 5 Me 5 ) 2 Th(N 3 )2] ∞ , and a new class of monometallic uranium bis(azide) complexes, (C 5 Me 5 ) 2 U(N 3 )2(O=PR 3 ), respectively. Full characterization of the novel complexes (C 5 Me 5 ) 2 ThF 2 (py) and (C 5 Me 5 ) 2 UF 2 (O=PR 3 ) are reported, including the solid-state structures of (C 5 Me 5 ) 2 ThF 2 (py) and (C 5 Me 5 ) 2 U(N 3 ) 2 (O=PPh 3 ). Lastly, electronic absorption spectral data are also reported for (C 5 Me 5 ) 2 AnF 2 (py) (An = Th, U) and (C 5 Me 5 ) 2 U(N 3 ) 2 (O=PR 3 ) to confirm metal oxidation state and enable elucidation of the fluoride and azide ligand bonding in these complexes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

High-entropy Li-rich layered oxide cathode for Li-ion batteries

High-entropy oxides (HEOs) are emerging as promising cathode materials for Li-ion batteries (LIBs) due to their stable solid-state phase and compositional flexibility. Herein, we investigate the structural and electrochemical properties of a novel non-equimolar high-entropy cathode material, termed high-entropy Li-rich layered oxide (HE-LLO, Li 1.15 Na 0.05 Ni 0.19 Mn 0.56 Fe 0.02 Mg 0.02 Al 0.02 O 1.97 F 0.03 ), in comparison to a pristine Li-rich layered oxide (PR-LLO, Li1.2Ni0.2Mn0.6O2). The incorporation of multiple cations (Na + , Al 3+ , Mg 2+ , Fe 3+ ) and anion (F - ) into HE-LLO introduces compositional diversity, enhancing structural stability through the entropy stabilization effect. Theoretical calculations confirm a significantly higher configurational entropy in HE-LLO compared to PRLLO, supporting its high-entropy nature. Electrochemical evaluations demonstrate that HE-LLO exhibits considerable capacity retention, preserving 76.8 % of its discharge capacity at 0.5C after 200 cycles, compared to only 36.2 % for PR-LLO. Even under high-temperature conditions, HE-LLO outperformed PR-LLO, maintaining 76.1 % of its discharge capacity after 100 cycles at 5C, while PR-LLO retained only 12.4 %. These enhancements are attributed to the improved phase reversibility and higher Li + ion diffusion coefficients of HE-LLO, validated by ex-situ characterizations using a synchrotron X-ray technique, along with density functional theory (DFT) calculations. In conclusion, these findings highlight the promise of non-equimolar HEOs as a novel design strategy for highperformance cathode materials.

25 ENERGY STORAGE↗

DOE OSTI2016

Synthesis, crystal structure, and magnetism of A{sub 2}Co{sub 12}As{sub 7} (A=Ca, Y, Ce–Yb)

Ternary intermetallics, A{sub 2}Co{sub 12}As{sub 7} (A=Ca, Y, Ce–Yb), have been synthesized by annealing mixtures of elements in molten Bi at 1223 K. The materials obtained crystallize in the P6{sub 3}/m variant of the Zr{sub 2}Fe{sub 12}P{sub 7} structure type. The unit cell volume shows a monotonic decrease with the increasing atomic number of the rare-earth metal, with the exception of Ce-, Eu-, and Yb-containing compounds. An examination of these outliers with X-ray absorption near edge structures (XANES) spectroscopy revealed mixed valence of Ce, Eu, and Yb, with the average oxidation states of +3.20(1), +2.47(5), and +2.91(1), respectively, at room temperature. Magnetic behavior of A{sub 2}Co{sub 12}As{sub 7} is generally characterized by ferromagnetic ordering of Co 3d moments at 100–140 K, followed by low-temperature ordering of rare-earth 4f moments. The 3d-4f magnetic coupling changes from antiferromagnetic for A=Pr–Sm to ferromagnetic for A=Ce and Eu–Yb. Polarized neutron scattering experiments were performed to support the postulated ferro- and ferrimagnetic ground states for Ce{sub 2}Co{sub 12}As{sub 7} and Nd{sub 2}Co{sub 12}As{sub 7}, respectively. - Graphical abstract: Title arsenides were synthesized by Bi‐flux method. They exhibit mixed valence for A = Ce, Eu, Yb, ferrimagnetism for A = Ca, Y, Pr–Sm, and ferromagnetism for A = Eu–Tm. - Highlights: • A2Co12As7 (A=Ca, Y, Ce–Yb) were synthesized in Bi flux. • Ce, Eu, Yb exhibit mixed valence in the corresponding structures. • The character of 3d‐4f magnetic coupling changes at the half‐filled f shell. • Materials behave as ferrimagnets for A=Ca, Y, Pr–Sm and as ferromagnets for A=Eu–Yb.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Nuclear Structure and Decay Data for A=149 Isobars

Here, experimental nuclear structure and decay data are evaluated for all the 17 known nuclides of mass 149 (Xe, Cs, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb). Detailed compiled and evaluated spectroscopic information is presented for each reaction and decay dataset, and recommended values are provided for level properties, α, β and γ radiations, and other spectroscopic parameters, based on an evaluation of all the available experimental data for A=149 isobaric nuclides. Although large amounts of nuclear spectroscopic data are available for nuclides of A=149, yet large gaps in knowledge exist, as described below. For the lowest atomic number nuclide 149 Xe, only the isotopic identification has been made, with no data for its ground-state half-life. For 149 Cs, 149 Tm and 149 Yb information is available for only the respective ground states. For 149 Ba, 149 La and 149 Er, limited data exist for excited states. Many of the decay schemes of radioactive nuclei of A=149 are considered as incomplete, either due to large energy differences between the highest observed excited states in daughter nuclides and the respective Q-values, or due to the lack of confirmed γ-ray data, as listed below: 149 Cs → 149 Ba, 149 Ba → 149 La, 149 La → 149 Ce, 149 Ce → 149 Pr, 149 Pr → 149 Nd, 149 Tb(4.17 min) → 149 Gd, 149 Ho(21.0 s and 56 s) → 149 Dy, 149 Er(4 s and 9.6 s) → 149 Ho, and 149 Tm → 149 Er. No data exist for the decay of 149 Yb to 149 Tm. Data for half-lives of the excited states in this mass chain are generally lacking as given below by the number of excited levels of known half-life / approximate number of known levels in a nuclide: 2/17 for 149 Ba, 0/18 for 149 La, 3/53 for 149 Ce, 3/44 for 149 Pr, 17/110 for 149 Nd, 9/90 for 149 Pm, 10/210 for 149 Sm, 2/125 for 149 Eu, 6/270 for 149 Gd, 5/200 for 149 Tb, 3/80 for 149 Dy, 3/90 for 149 Ho, and 3/14 for 149 Er. This work supersedes earlier evaluations of A=149 nuclides published by 2004Si16, 1994Si18, 1985Sz01 and 1976Ho17.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2015

Scaling of heat transport near onset in rapidly rotating convection

Here, we consider the scaling of heat transport in the geostrophic regime of rotating Rayleigh–Bénard convection near onset for small Ekman number Ek from the perspective of weakly nonlinear theory. We show that available heat transport data from numerical simulation [1] for Ek < 10 -5 for Pr = 1 are consistent with weakly nonlinear theory for ϵ = Ra / Ra c - 1 < 1. In particular, we show that the numerical data are consistent with Nu - 1 = aϵ + bϵ 2 with a ≈ 2 and b ≈ 3 with weak dependence of the coefficients on Ek. The coefficient a is consistent with calculations of weakly nonlinear theory and with experimental data at much higher Ek. The positive sign of b is also suggested by those experimental data. The magnitude and trend of the numerical data for larger Ra are consistent with experimental data with similar Pr ~ 1. The steep scaling of Nu ~ (Ra / Ra c ) 3 noted elsewhere for Ra / Ra c < 2 is shown to be an artifact of being close to onset where the effective power-law slope depends sensitively on the magnitude of the coefficients a and b. Similar arguments apply to Pr = 7 numerical data although the weakly nonlinear expansion appears valid for a smaller range of ϵ than in the Pr = 1 case.

58 GEOSCIENCES↗

DOE OSTI2024

Prandtl number effects on extreme mixing events in forced stratified turbulence

Relatively strongly stratified turbulent flows tend to self-organise into a ‘layered anisotropic stratified turbulence’ (LAST) regime, characterised by relatively deep and well-mixed density ‘layers’ separated by relatively thin ‘interfaces’ of enhanced density gradient. Understanding the associated mixing dynamics is a central problem in geophysical fluid dynamics. It is challenging to study LAST mixing, as it is associated with Reynolds numbers $Re := UL/\nu \gg 1$ and Froude numbers $Fr :=(2{\rm \pi} U)/(L N) \ll 1$ ( $U$ and $L$ being characteristic velocity and length scales, $\nu$ the kinematic viscosity and $N$ the buoyancy frequency). Since a sufficiently large dynamic range (largely) unaffected by stratification and viscosity is required, it is also necessary for the buoyancy Reynolds number $Re_{b} := \epsilon /(\nu N^{2}) \gg 1$ , where $\epsilon$ is the (appropriately volume-averaged) turbulent kinetic energy dissipation rate. This requirement is exacerbated for oceanically relevant flows, as the Prandtl number $Pr := \nu /\kappa = {O}(10)$ in thermally stratified water (where $\kappa$ is the thermal diffusivity), thus leading (potentially) to even finer density field structures. We report here on four forced fully resolved direct numerical simulations of stratified turbulence at various Froude ( $Fr=0.5, 2$ ) and Prandtl ( $Pr=1, 7$ ) numbers forced so that $Re_{b}=50$ , with resolutions up to $30\,240 \times 30\,240 \times 3780$ . We find that, as $Pr$ increases, emergent ‘interfaces’ become finer and their contribution to bulk mixing characteristics decreases at the expense of the small-scale density structures populating the well-mixed ‘layers’. However, extreme mixing events (as quantified by significantly elevated local destruction rates of buoyancy variance $\chi _0$ ) are always preferentially found in the (statically stable) interfaces, irrespective of the value of $Pr$ .

Mechanics↗

DOE OSTI2022

Phosphine Ligand Binding and Catalytic Activity of Group 10–14 Heterobimetallic Complexes

We report heterobimetallic complexes have attracted much interest due to their broad range of structures and reactivities as well as unique catalytic abilities. Additionally, these complexes can be utilized as single-source precursors for the synthesis of binary intermetallic compounds. An example is the family of bis(pyridine-2-thiolato)dichloro-germanium and tin complexes of group 10 metals (Pd and Pt). The reactivity of these heterobimetallic complexes is highly tunable through substitution of the group 14 element and the neutral ligand bound to the transition metal. Here, we study the binding energies of three different phosphorous-based ligands, PR 3 (R = Bu, Ph, and OPh) by density functional theory and restricted Hartree–Fock methods. The PR 3 ligand-binding energies follow the trend of PBu 3 > PPh 3 > P(OPh) 3 , in agreement with their sigma-bonding ability. These results are confirmed by ligand exchange experiments monitored with 31 P NMR spectroscopy, in which a weaker binding PR 3 ligand is replaced with a stronger one. Furthermore, we demonstrate that the heterobimetallic complexes are active catalysts in the Negishi coupling reaction, where stronger binding PR 3 ligands inhibit access to an active site at the metal center. Similar strategies could be applied to other complexes to better understand their ligand-binding energetics and predict their reactivity as both precursors and catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Facile Oxidation of Ce(III) to Ce(IV) Using Cu(I) Salts

The synthesis, luminescence, and electrochemical properties of the Ce(III) compound, [(C 5 Me 5 )2(2,6- i Pr 2 C 6 H 3 O)Ce(THF)], 1, were investigated. Based on the electrochemical data, treatment of 1 with CuX (X = Cl, Br, I) results in the formation of the corresponding Ce(IV) complexes, [(C 5 Me 5 ) 2 (2,6- i Pr 2 C 6 H 3 O)Ce(X)]. Each complex has been characterized using NMR, IR, and UV−vis spectroscopy as well as structurally determined using X-ray crystallography. Additionally, the treatment of [(C 5 Me 5 ) 2 (2,6- i Pr 2 C 6 H 3 O)Ce(Br)] with AgF results in the formation of the putative [(C 5 Me 5 ) 2 (2,6- i Pr 2 C 6 H 3 O)Ce(F)]. Furthermore, the electronic structure of these Ce(IV)−X complexes was investigated by bond analyses and the Ce(IV)−F moiety using quantum chemistry NMR calculations.

Aromatic compounds↗

DOE OSTI2018

Proline- and Arginine-Rich Peptides as Flexible Allosteric Modulators of Human Proteasome Activity

Proline- and arginine-rich peptide PR11 is an allosteric inhibitor of 20S proteasome. We modified its sequence inter alia by introducing HbYX, RYX, or RHbX C-terminal extensions (Hb, hydrophobic moiety; R, arginine; Y, tyrosine; X, any residue). Consequently, we were able to improve inhibitory potency or to convert inhibitors into strong activators: the former with an aromatic penultimate Hb residue and the latter with the HbYX motif. The PR peptide activator stimulated 20S proteasome in vitro to efficiently degrade protein substrates, such as α-synuclein and enolase, but also activated proteasome in cultured fibroblasts. The positive and negative PR modulators differently influenced the proteasome conformational dynamics and affected opening of the substrate entry pore. The resolved crystal structure showed PR inhibitor bound far from the active sites, at the proteasome outer face, in the pocket used by natural activators. Overall, our studies indicate the opportunity to tune proteasome activity by allosteric regulators based on PR peptide scaffold.

60 APPLIED LIFE SCIENCES↗