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Gas-phase reactions of [OsC] and [IrC] with methane at ambient temperature have been studied using quadrupole-ion trap mass spectrometry combined with quantum chemical calculations. Both [OsC] and [IrC] undergo carbon-atom exchange reactions with methane. The associated mechanisms for the two systems are found to be similar. The differences in the rates of carbon isotope exchange reactions of methane with [MC] (M = Os and Ir) are explained by several factors like the energy barrier for the initial HC-H bond breaking processes, the molecular dynamics, orbital interactions, and the H-binding energies of the pivotal steps. Besides, the number of participating valence orbitals might be one of the keys to regulate the rate in the key step. The present findings may provide useful ideas and inspiration for designing similar processes.
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http://dx.doi.org/10.1021/acs.jpca.3c07961 | DOI Listing |
J Phys Chem B
July 2025
Department of Chemistry, New York University, New York, New York 10003, United States.
The guanidine moiety of arginine side chains in proteins is often close to branched aliphatic side chains. We used the dispersion-corrected ωB97X-D density functional to calculate the interaction energy between the models of Arg and Leu side chains. We found that, in the lowest energy planar-like structures, the amino groups of methylguanidinium ion─our model of Arg side chains, and the methyl groups of 2-methylbutane─our model of leucine or isoleucine side chains, approach each other very closely.
View Article and Find Full Text PDFJ Chem Phys
April 2025
Theoretical Physics IV, University of Bayreuth, 95447 Bayreuth, Germany.
We provide accurate energies and electronic densities for Li2, C, and N2 from the diffusion Monte Carlo (DMC) method in the fixed node approximation based on orbitals from a real-space grid approach. With relatively simple single-determinant trial wave functions, we demonstrate the benefits of an all-electron approach in conjunction with a highly accurate grid method for calculating the orbitals that build the determinant. Our DMC ground state energies match with those of more elaborate single-reference quantum Monte Carlo (QMC) methods based on orbital basis sets.
View Article and Find Full Text PDFACS Appl Mater Interfaces
April 2025
School of Energy and Chemical Engineering, UNIST, Ulsan 44919, South Korea.
It is challenging to selectively promote the two-electron oxygen reduction reaction (2e-ORR) since highly ORR-active electrocatalysts are not satisfied with 2e-ORR and are most likely to go all the way to 4e-ORR, completely reducing dioxygen to water. Recently, however, the possibility of a 2e-ORR preference over 4e-ORR was raised by extensively considering multiple ORR mechanisms and employing a potential-dependent activity measure for constructing volcano plots. Here, we realized the preferred 2e-ORR via an intramolecular double activation of the peroxide intermediate (*OOH) by allowing the intermediate to be easily desorbed before proceeding to 4e-ORR.
View Article and Find Full Text PDFJ Am Chem Soc
February 2025
Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States.
The tearing of a polymer network arises from mechanochemically coupled bond-breaking events in the backbone of a polymer chain. An emerging research area is the identification of molecular strategies for network toughening, such as the strategic placement of mechanochemically reactive groups (e.g.
View Article and Find Full Text PDFChemistry
February 2025
Laboratory of Catalysis, MolSys Research Unit, Université de Liège, Institut de Chimie Organique (B6a), Allée du six Août 13, 4000, Liège, Belgium.
Thirteen imidazolium iodides bearing benzyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms, and C-C alkyl chains on their C2 carbon atom were readily deuterated with DO as a cheap and non-toxic deuterium source in the presence of CsCO, a weak, innocuous, inorganic base. The isotopic exchange proceeded quickly and efficiently under mild, aerobic conditions to afford a range of aNHC and NHO precursors regioselectively labeled on their C2α exocyclic position and/or C4=C5 heterocyclic backbone. A "carbene-free" mechanism was postulated, in which the carbonate anion acts as a catalyst to activate an exocyclic, acidic C-H bond and ease a deuterium transfer from DO to the imidazolium salt in a concerted fashion.
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