SABRE hyperpolarization of nicotinamide derivatives and their molecular dynamics properties

Luu, Quy Son; Nguyen, Quynh Thi; Manh, Hung Ngo; Yun, Seokki; Kim, Jiwon; Do, Uyen Thi; Jeong, Keunhong; Lee, Sang Uck; Lee, Youngbok

doi:10.1039/d3an02053c

Cited by 2 publications

References 43 publications

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Analysis of chemical exchange in iridium N-heterocyclic carbene complexes using heteronuclear parahydrogen-enhanced NMR

Assaf,

Gui,

Salnikov

et al. 2024

Commun Chem

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The signal amplification by reversible exchange process (SABRE) enhances 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 focus on optimizing polarization transfer from 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, with readout occurring at 15N nuclei directly interacting with the catalyst. Enhanced 15N NMR signals overcome sensitivity challenges, encoding substrate dissociation rates. This methodology enables robust data fitting to ligand exchange models, yielding substrate dissociation rate constants with higher precision than classical 1D and 2D 1H NMR approaches. This refinement improves the accuracy of key activation enthalpy ΔH‡ and entropy ΔS‡ estimates. Furthermore, the higher chemical shift dispersion provided by enhanced 15N NMR reveals the kinetics of substrate dissociation for acetonitrile and metronidazole, previously inaccessible via 1H NMR due to small chemical shift differences between free and Ir-bound substrates. The presented approach can be successfully applied not only to isotopically enriched substrates but also to compounds with natural abundance of the to-be-hyperpolarized heteronuclei.

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Analysis of chemical exchange in iridium N-heterocyclic carbene complexes using heteronuclear parahydrogen-enhanced NMR

Assaf,

Gui,

Salnikov

et al. 2024

Commun Chem

View full text Add to dashboard Cite

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

Assaf,

Gui,

Salnikov

et al. 2024

Preprint

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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.

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SABRE hyperpolarization of nicotinamide derivatives and their molecular dynamics properties

Abstract: Signal amplification by reversible exchange hyperpolarization explores the chemical structure and kinetic properties of nicotinamide derivatives. N-benzyl nicotinamide and nicotinic acid hydrazide compounds display relatively fast dissociation rates of approximately...

Cited by 2 publications

References 43 publications

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

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

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