Temperature-Dependent Solid-State NMR Proton Chemical-Shift Values and Hydrogen Bonding

Malär, Alexander A.; Völker, Laura A.; Cadalbert, Riccardo; Lecoq, Lauriane; Ernst, Matthias; Böckmann, Anja; Meier, Beat H.; Wiegand, Thomas

doi:10.26434/chemrxiv.14230043

Cited by 2 publications

(2 citation statements)

References 37 publications

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“…8c). The resonances of ortho-phospho-L-serine reported in the experimental section (the methylene CH 2 and the CαH protons) do not show a measurable temperature dependence of the chemical-shift values as described recently (Malär et al, 2021).…”

Section: Experimental Datasupporting

confidence: 59%

Residual dipolar line width in magic-angle spinning proton solid-state NMR

et al. 2021

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Abstract. Magic-angle spinning is routinely used to average anisotropic interactions in solid-state nuclear magnetic resonance (NMR). Due to the fact that the homonuclear dipolar Hamiltonian of a strongly coupled spin system does not commute with itself at different time points during the rotation, second-order and higher-order terms lead to a residual dipolar line broadening in the observed resonances. Additional truncation of the residual broadening due to isotropic chemical-shift differences can be observed. We analyze the residual line broadening in coupled proton spin systems based on theoretical calculations of effective Hamiltonians up to third order using Floquet theory and compare these results to numerically obtained effective Hamiltonians in small spin systems. We show that at spinning frequencies beyond 75 kHz, second-order terms dominate the residual line width, leading to a 1/ωr dependence of the second moment which we use to characterize the line width. However, chemical-shift truncation leads to a partial ωr-2 dependence of the line width which looks as if third-order effective Hamiltonian terms are contributing significantly. At slower spinning frequencies, cross terms between the chemical shift and the dipolar coupling can contribute in third-order effective Hamiltonians. We show that second-order contributions not only broaden the line, but also lead to a shift of the center of gravity of the line. Experimental data reveal such spinning-frequency-dependent line shifts in proton spectra in model substances that can be explained by line shifts induced by the second-order dipolar Hamiltonian.

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Section: Experimental Datasupporting

confidence: 59%

Residual dipolar line width in magic-angle spinning proton solid-state NMR

et al. 2021

Self Cite

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show abstract

Section: Experimental Datasupporting

confidence: 59%

Residual Linewidth in Magic-Angle Spinning Solid-State NMR

Chávez¹,

Wiegand²,

Malär³

et al. 2021

Preprint

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Abstract. Magic-angle spinning is routinely used to average anisotropic interactions in solid-state NMR. Due to the fact, that the Hamiltonian of a strongly-coupled spin system does not commute with itself at different time points during the rotation, second-order and higher-order terms lead to a residual line broadening in the observed resonances. Additional truncation of the residual broadening due to isotropic chemical-shift differences can be observed. We analyze the residual line broadening in coupled proton spin systems based on theoretical calculations of effective Hamiltonians up to third order using Floquet theory and compare these results to numerically obtained effective Hamiltonians in small spin systems. We show that at spinning frequencies beyond 50 kHz, second-order terms dominate the residual line width leading to a 1/ωr dependence of the second moment which we use to characterize the line width. However, chemical-shift truncation leads to a partial ωr-2 dependence of the line width which looks as if third-order effective Hamiltonian terms are contributing significantly. We show that second-order contributions not only broaden the line but also lead to a shift of the center of gravity of the line. Experimental data reveals such spinning-frequency dependent line shifts in proton spectra in model substances that can be explained by line shifts induced by the second-order dipolar Hamiltonian.

show abstract

Temperature-Dependent Solid-State NMR Proton Chemical-Shift Values and Hydrogen Bonding

Cited by 2 publications

References 37 publications

Residual dipolar line width in magic-angle spinning proton solid-state NMR

Residual dipolar line width in magic-angle spinning proton solid-state NMR

Residual Linewidth in Magic-Angle Spinning Solid-State NMR

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