Improved NMR transfer of magnetization from protons to half-integer spin quadrupolar nuclei at moderate and high magic-angle spinning frequencies

Abstract. Half-integer spin quadrupolar nuclei are the only magnetic isotopes for majority of chemical elements. Therefore, transfer polarization from protons to these under magic-angle spinning (MAS) can provide precious insights into interatomic proximities in hydrogen-containing solids, including organic, hybrid, nanostructured and biological solids. This has recently been combined with dynamic nuclear (DNP) order enhance NMR signal half-integer isotopes. However, cross-polarization lacks robustness case nuclei, we have introduced as an alternative technique a D-RINEPT (through-space refocused insensitive enhancement by transfer) scheme combining heteronuclear dipolar recoupling built adiabatic pulses continuous-wave decoupling. demonstrated at 9.4 T moderate MAS frequencies, νR≈10–15 kHz, DNP-enhanced 1H nuclei. Nevertheless, transfers also required higher frequencies improve resolution. We investigate here how this be achieved νR≈20 60 kHz. demonstrate that sequence using still produces efficient robust but requires large radio-frequency (rf) fields, which may not compatible specifications most probes. As alternative, introduce variants PRESTO (phase-shifted effects smooth order) sequences symmetry-based schemes single composite π pulses. Their performances compared average Hamiltonian theory experiments B0=18.8 on γ-alumina isopropylamine-templated microporous aluminophosphate (AlPO4-14), featuring low significant 1H–1H interactions, respectively. These magnetization efficiently transferred 27Al SR412(270090180) R2227(1800) or R1676(270090180) νR=20 62.5 The complement each other since latter is affected truncation, whereas former not. analyze losses during schemes, show used νR=62.5 kHz acquire 72 min 2D HETCOR (heteronuclear correlation) spectra between non-uniform sampling (NUS).