title: Indirect detection via spin-1/2 nuclei in solid state NMR spectroscopy: application to the observation of proximities between protons and quadrupolar nuclei.
abstract: We present a comprehensive comparison of through-space heteronuclear correlation techniques for solid state NMR, combining indirect detection and single-channel recoupling method. These techniques, named D-HMQC and D-HSQC, do not suffer from dipolar truncation and can be employed to correlate quadrupolar nuclei with spin-1/2 nuclei. The heteronuclear dipolar couplings are restored under magic-angle spinning by applying supercycled symmetry-based pulse sequences (SR412) or simultaneous frequency and amplitude modulation (SFAM). The average Hamiltonian theory (AHT) of these recoupling methods is developed. These results are applied to analyze the performances of D-HMQC and D-HSQC sequences. It is shown that, whatever the magnitude of spin interations, D-HMQC experiment offers larger efficiency and higher robustness than D-HSQC. Furthermore, the spectral resolution in both dimensions of proton detected two-dimensional D-HMQC and D-HSQC spectra can be enhanced by applying recently introduced symmetry-based homonuclear dipolar decoupling schemes that cause a z-rotation of the spins. This is demonstrated by 1H-13C and 1H-23Na correlation experiments on l-histidine and NaH2PO4, respectively. The two-dimensional heteronuclear 1H-23Na correlation spectrum yields the assignment of 23Na resonances of NaH2PO4. This assignment is corroborated by first-principles calculations.
authors.affiliation: Unité de Catalyse et de Chimie du Solide (UCCS), UMR CNRS 8181, Ecole Nationale Supérieure de Chimie de Lille, Université de Lille 1, Batiment C7, B.P. 90108, 59652 Villeneuve d'Ascq Cedex, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Lafon
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wang
authors.forename: Bingwen
authors.initials: B
authors.lastname: Hu
authors.forename: Filipe
authors.initials: F
authors.lastname: Vasconcelos
authors.forename: Julien
authors.initials: J
authors.lastname: Trébosc
authors.forename: Sylvain
authors.initials: S
authors.lastname: Cristol
authors.forename: Feng
authors.initials: F
authors.lastname: Deng
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Amoureux
mesh_terms: D003198:Computer Simulation; D006639:Histidine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000592:standards; D008956:Models, Chemical; D010710:Phosphates / Q000737:chemistry*; D011522:Protons; D012015:Reference Standards; D012964:Sodium / Q000737:chemistry
chemical_list: D010710:Phosphates; D011522:Protons; D006639:Histidine; D012964:Sodium; C018279:sodium phosphate