Analysis of Chemical Exchange in Iridium N-Heterocyclic Carbene Complexes Using Heteronuclear Parahydrogen-Enhanced NMR

Analysis of Chemical Exchange in Iridium N-Heterocyclic Carbene Complexes Using Heteronuclear Parahydrogen-Enhanced NMR | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Analysis of Chemical Exchange in Iridium N-Heterocyclic Carbene Complexes Using Heteronuclear Parahydrogen-Enhanced NMR Charbel D. Assaf, Xin Gui, Oleg G. Salnikov, Arne Brahms, Nikita V. Chukanov, and 11 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4849274/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 03 Dec, 2024 Read the published version in Communications Chemistry → Version 1 posted You are reading this latest preprint version Abstract The signal amplification by reversible exchange process (SABRE) amplifies NMR signals by unlocking hidden polarization in parahydrogen through interactions with to-be-hyperpolarized substrate molecules when both are transiently bound to an Ir-based organometallic catalyst. Recent efforts have focused on optimizing the polarization transfer step from the parahydrogen-derived hydride ligands to the substrate in SABRE. However, this requires quantitative information on ligand exchange rates, which common NMR techniques struggle to provide. Here, we introduce an experimental spin order transfer sequence where readout occurs at 15N nuclei directly interacting with the catalyst. To overcome sensitivity challenges, enhanced 15N NMR signals are created, encoding discrete substrate dissociation rates. This methodology enables robust data fitting to proposed ligand exchange models, yielding substrate dissociation rate constants with higher precision than classical 1D and 2D 1H NMR approaches. This refinement provides enhanced accuracy for estimating the key activation enthalpy ΔH‡ and ΔS‡. Moreover, the higher chemical shift dispersion provided by signal-enhanced 15N NMR allows for the kinetics of substrate dissociation of both acetonitrile and metronidazole, previously inaccessible via 1H NMR due to small chemical shift differences between the resonances of free and Ir-bound molecules of these substrates. Physical sciences/Chemistry/Analytical chemistry/NMR spectroscopy/Solution-state NMR Physical sciences/Chemistry/Physical chemistry/Reaction kinetics and dynamics Full Text Additional Declarations Yes there is potential Competing Interest. E.Y.C. declares a stake of ownership in XeUS Technologies LTD and Vizma Life Sciences. E.Y.C. serves on the Scientific Advisory Board (SAB) of Vizma Life Sciences. Supplementary Files SupportingInformation.docx Cite Share Download PDF Status: Published Journal Publication published 03 Dec, 2024 Read the published version in Communications Chemistry → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4849274","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":337216619,"identity":"b1840321-893e-4116-8569-82f08061de6f","order_by":0,"name":"Charbel D. 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