Products Cited in Publications Worldwide Indirect Detection of Wideline Magic Angle Spinning Solid-state NMR Spectra of Spin-5/2,-7/2, and-9/2 Half-Integer Quadrupolar Nuclei

Indirect Detection of Wideline Magic Angle Spinning Solid-state NMR Spectra of Spin-5/2,-7/2, and-9/2 Half-Integer Quadrupolar Nuclei

Lamahewage, Sujeewa NS; Li, Yuting; Sadow, Aaron D; Rossini, Aaron J

DOI:

Abstract

Quadrupolar nuclei with a nuclear spin I > 1/2 account for ~73% of all NMR-active nuclei. The quadrupolar interaction broadens the solid-state NMR signals, frequently resulting in low resolution and poor sensitivity. Here, we present a theoretical and experimental investigation of the use of magic angle spinning (MAS) 1H{X} double-echo resonance-echo saturation-pulse double-resonance (DE-RESPDOR) solid-state NMR experiments for the indirect detection of n half-integer quadrupolar nuclei with spin > 3/2 (spin 5/2, 7/2, or 9/2 nuclei). In these experiments, plotting the observed dephasing of the detected spin as a function of the transmitter offset of the indirectly detected spin allows for the reconstruction of the spectrum of the quadrupolar nucleus. The achievable dephasing levels and the lineshapes of solid-state NMR spectra of the indirectly detected nuclei were predicted using numerical simulations. We demonstrate 1H detection of 127I (I = 5/2), 139La (I = 7/2), and 115In (I = 9/2) nuclei in BaI2.2H2O (barium iodide dihydrate), La(BH4)3(THF)3 (tris(borohydride)tris(tetrahydrofuran)lanthanum(III)), and In(OH)3 (indium(III) hydroxide), respectively. The observed improvements or reductions in sensitivity with indirect detection are related to the proportion of 1H T1 to quadrupolar nucleus T1, alongside the quadrupolar nucleus's spin quantum number and gyromagnetic ratio (γ). Additionally, the indirect detection experiments confirm the existence of dipolar or scalar couplings between the detected nucleus and the quadrupolar nucleus of interest, providing important structural information. Numerical simulations suggest these methods are also potentially applicable to quadrupolar nuclei having large quadrupolar coupling constants.

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