Measuring strong one-bond dipolar couplings using REDOR in magic-angle spinning solid-state NMR
| Autor: | Kaustubh R. Mote, Perunthiruthy K. Madhu, Matthias Ernst, Vipin Agarwal, Mukul G. Jain, Johannes Hellwagner, G. Rajalakshmi |
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| Rok vydání: | 2019 |
| Předmět: |
Physics
010304 chemical physics Dephasing General Physics and Astronomy 010402 general chemistry 01 natural sciences Resonance (particle physics) Molecular physics 3. Good health 0104 chemical sciences symbols.namesake Fourier transform Solid-state nuclear magnetic resonance 0103 physical sciences Magic angle spinning symbols Physical and Theoretical Chemistry Spin (physics) Scaling Magnetic dipole–dipole interaction |
| Zdroj: | The Journal of Chemical Physics, 150 (13) |
| ISSN: | 1089-7690 |
| Popis: | Rotational-Echo DOuble Resonance, REDOR, is an experimentally robust and a well-established dipolar-recoupling technique to measure dipolar couplings between isolated pairs of spin-1/2 heteronuclei in solid-state nuclear magnetic resonance. REDOR can also be used to estimate motional order parameters when the bond distance is known, for example, in the case of directly bound nuclei. However, the relatively fast dipolar dephasing for strongly coupled spin-1/2 pairs, such as 13C–1H, makes the stroboscopic measurement required in this experiment challenging, even at fast Magic-Angle-Spinning (MAS) frequencies. In such cases, modified REDOR-based methods like Shifted-REDOR (S-REDOR) are used to scale the dipolar coupling compared to REDOR. This is achieved by changing the position of one of the two recoupling π-pulses in a rotor period. This feature, however, comes at the cost of mixing multiple Fourier components of the dipolar coupling and can, additionally, require high radio-frequency amplitudes to realise small scaling factors. We introduce here a general pulse scheme which involves shifting both the π pulses in the REDOR scheme to achieve arbitrary scaling factors whilst retaining the robustness and simplicity of REDOR recoupling and avoiding the disadvantages of S-REDOR. The classical REDOR is a specific case of this scheme with a scaling factor of one. We demonstrate the results on isolated 13C–15N and 1H–13C spin pairs at 20 and 62.5 kHz MAS, respectively. |
| Databáze: | OpenAIRE |
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