More Like this

1. In silico screening of P , N -ligands facilitates optimization of Au( iii )-mediated S -arylation

   https://doi.org/10.1039/D4SC05920D  

   Treacy, Joseph W; Tilden, James_A R; Chao, Elaine Y; Fu, Zihuan; Spokoyny, Alexander M; Houk, K N; Maynard, Heather D (February 2025, Chemical Science)

   In silicoexamination of 13P,N-ligated Au(iii) OACs determined the key mechanistic factors governing Au(iii)-mediatedS-arylation. Three complexes were synthesized which exhibited bimolecular coordination rate constants as high as 20 200 M⁻¹s⁻¹. 

   more » « less
2. Improved thermonuclear rate of ⁴² Ti( p , γ ) ⁴³ V and its astrophysical implication in the rp process

   https://doi.org/10.1051/0004-6361/202347054  

   Hou, S Q; Iliadis, C; Pignatari, M; Liu, J B; Trueman, T_C L; Li, J G; Xu, X X (September 2023, Astronomy & Astrophysics)

   Context.Accurate⁴²Ti(p,γ)⁴³V reaction rates are crucial for understanding the nucleosynthesis path of the rapid capture process (rpprocess) that occurs in X-ray bursts. Aims.We aim to improve the thermonuclear rates of⁴²Ti(p,γ)⁴³V based on more complete resonance information and a more accurate direct component, together with the recently released nuclear masses data. We also explore the impact of the newly obtained rates on therpprocess. Methods.We reevaluated the reaction rate of⁴²Ti(p,γ)⁴³V by the sum of the isolated resonance contribution instead of the Hauser-Feshbach statistical model. We used a Monte Carlo method to derive the associated uncertainties of new rates. The nucleosynthesis simulations were performed via the NuGrid post-processing code ppn. Results.The new rates differ from previous estimations due to the use of a series of updated resonance parameters and a direct S factor. Compared with the previous results from the Hauser-Feshbach statistical model, which assumes compound nucleus⁴³V with a sufficiently high-level density in the energy region of astrophysical interest, large differences exist over the entire temperature region ofrp-process interest, up to two orders of magnitude. We consistently calculated the photodisintegration rate using our new nuclear masses via the detailed balance principle, and found the discrepancies among the different reverse rates are much larger than those for the forward rate, up to ten orders of magnitude at the temperature of 10⁸K. Using a trajectory with a peak temperature of 1.95×10⁹K, we performed therp-process nucleosynthesis simulations to investigate the impact of the new rates. Our calculations show that the adoption of the new forward and reverse rates result in abundance variations for Sc and Ca of 128% and 49%, respectively, compared to the variations for the statistical model rates. On the other hand, the overall abundance pattern is not significantly affected. The results of using new rates also confirm that therp-process path does not bypass the isotope⁴³V. Conclusions.Our study found that the Hauser-Feshbach statistical model is inappropriate to the reaction rate evaluation for⁴²Ti(p,γ)⁴³V. The adoption of the new rates confirms that the reaction path of⁴²Ti(p,γ)⁴³V(p,γ)⁴⁴Cr(β⁺)⁴⁴V is a key branch of therpprocess in X-ray bursts. 

   more » « less
3. N -[6-(Dimethylamino)-9-phenyl-3 H -telluroxanthen-3-ylidene]- N -methylmethanaminium hexafluorophosphate monoclinic polymorph

   https://doi.org/10.1107/S2414314621005459  

   Myers, Shea; Johnson, Patrick; Benedict, Jason B (June 2021, IUCrData)

   The title compound C₂₃H₂₃N₂Te⁺·PF₆⁻, is a monoclinic polymorph of the previously reported triclinic structure [Calitreeet al.(2007).Organometallics,26, 6248–6257]. In the crystal, parallel offset π–π stacking [shortest centroid–centroid separation = 3.9620 (9) Å] and ionic interactions help to establish the packing. 

   more » « less
4. Calcium‐Ion Binding Mediates the Reversible Interconversion of Cis and Trans Peroxido Dicopper Cores

   https://doi.org/10.1002/anie.202105421  

   Vargo, Natasha P.; Harland, Jill B.; Musselman, Bradley W.; Lehnert, Nicolai; Ertem, Mehmed Z.; Robinson, Jerome R. (July 2021, Angewandte Chemie International Edition)

   Abstract Coupled dinuclear copper oxygen cores (Cu₂O₂) featured in type III copper proteins (hemocyanin, tyrosinase, catechol oxidase) are vital for O₂transport and substrate oxidation in many organisms.μ‐1,2‐cisperoxido dicopper cores (^CP) have been proposed as key structures in the early stages of O₂binding in these proteins; their reversible isomerization to other Cu₂O₂cores are directly relevant to enzyme function. Despite the relevance of such species to type III copper proteins and the broader interest in the properties and reactivity of bimetallic^CPcores in biological and synthetic systems, the properties and reactivity of^CPCu₂O₂species remain largely unexplored. Herein, we report the reversible interconversion ofμ‐1,2‐transperoxido (^TP) and^CPdicopper cores. Ca^IImediates this process by reversible binding at the Cu₂O₂core, highlighting the unique capability for metal‐ion binding events to stabilize novel reactive fragments and control O₂activation in biomimetic systems. 

   more » « less
5. The Neumann function and the L ^p Neumann problem in chord-arc domains

   https://doi.org/10.1515/ans-2023-0171  

   Hofmann, Steve; Sparrius, Derek (February 2025, Advanced Nonlinear Studies)

   Abstract We construct the Neumann function in a 1-sided chord-arc domain (i.e., a uniform domain with an Ahlfors regular boundary), and establish size and Hölder continuity estimates up to the boundary. We then obtain a Kenig-Pipher type theorem, in whichL^psolvability of the Neumann problem is shown to yield solvability inL^qfor 1 <q<p, and in the Hardy spaceH¹, in 2-sided chord-arc domains, under suitable background hypotheses. 

   more » « less