Homoleptic eightfold coordinated methyl isocyanide complexes of W(IV) and W(V) have been prepared for the first time. The reaction of [NBu][W(CN)] with methyl triflate (MeOTf) gives [W(CNMe)][OTf]. The even stronger methylating mixture of methyl fluoride (MeF) and arsenic pentafluoride (AsF) in liquid sulfur dioxide (SO) is able to fully alkylate both [NBu][W(CN)] and [NBu][W(CN)]. The paramagnetic octakis(methyl isocyanide)tungsten(V) complex [W(CNMe)][AsF] is thermally highly unstable above -30 °C. All compounds have been characterized via single-crystal X-ray diffraction and IR, Raman, and NMR or EPR spectroscopy.
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http://dx.doi.org/10.1021/acs.inorgchem.1c00326 | DOI Listing |
Nucleic Acids Res
December 2024
Department of Chemistry, 5735 South Ellis Avenue, The University of Chicago, Chicago, IL 60637, USA.
The RNA World hypothesis posits that RNA was the molecule of both heredity and function during the emergence of life. This hypothesis implies that RNA templates can be copied, and ultimately replicated, without the catalytic aid of evolved enzymes. A major problem with nonenzymatic template-directed polymerization has been the very poor copying of sequences containing rA and rU.
View Article and Find Full Text PDFLife (Basel)
April 2024
Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA, UK.
Giant impacts can generate transient hydrogen-rich atmospheres, reducing atmospheric carbon. The reduced carbon will form hazes that rain out onto the surface and can become incorporated into the crust. Once heated, a large fraction of the carbon is converted into graphite.
View Article and Find Full Text PDFFaraday Discuss
July 2023
Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
Nitrogenases catalyse the 6-electron reduction of dinitrogen to ammonia, passing through a series of redox and protonation levels during catalytic substrate reduction. The molybdenum-iron nitrogenase is the most well-studied, but redox potentials associated with proton-coupled transformations between the redox levels of the catalytic MoFe protein have proved difficult to pin down, in part due to a complex electron-transfer pathway from the partner Fe protein, linked to ATP-hydrolysis. Here, we apply electrochemical control to the MoFe protein of nitrogenase, using europium(III/II)-ligand couples as low potential redox mediators.
View Article and Find Full Text PDFJ Phys Chem A
December 2022
KU Leuven, Department of Chemistry, Celestijnenlaan 200F, B-3001Leuven, Belgium.
Several nitrogen-bearing molecules, such as methyl cyanide (or acetonitrile, CHCN) and methyl isocyanide (CHNC) of interest here, have been observed in various astrophysical environments. The accurate modeling of their abundance requires the calculation of rate coefficients for their collisional excitation with species such as He atoms or H molecules at low temperatures. In this work we compute new three-dimensional potential energy surfaces for the CHNC-He and CHCN-He van der Waals complexes by means of the explicitly correlated coupled cluster approach with single, double and perturbative triple excitation CCSD(T)/F12a in conjunction with the aug-cc-pVTZ basis set.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
April 2022
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138.
Nonenzymatic template-directed RNA copying using chemically activated nucleotides is thought to have played a key role in the emergence of genetic information on the early Earth. A longstanding question concerns the number and nature of different environments that might have been necessary to enable all of the steps from nucleotide synthesis to RNA copying. Here we explore three sequential steps from this overall pathway: nucleotide activation, synthesis of imidazolium-bridged dinucleotides, and template-directed RNA copying.
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