Indirect Coupling and Connectivity

Advances in the characterization of inorganic solids using NMR correlation experiments

“…This experiment as well as 2D 13 C{ 1 H} CP-HETCOR and more recently, DNP-enhanced 13 C{ 31 P} CP-HETCOR experiments have provided information about the location of anionic substituents in calcium phosphate phases 394,403,404 . Heteronuclear correlation between protons and 43 Ca isotope, which is low-γ quadrupolar nucleus (I = 7/2 and |γ( 43 Ca)/γ( 1 H)| = 6.7%), has also been reported, first for 43 Ca-enriched hydroxyapatite and oxyhydroxyapatite 287 and more recently, in natural abundance (0.14%) using DNP for carbonated hydroxyapatite (see Figure 33b). S{ 1 H} CP-HETCOR experiments with S = 13 C 196,405,406 , 19 F 196 and 29 Si 405,407,406,408,409 have also been applied to study clay minerals and notably their interactions with organic cations and molecules.…”

“…Inorganic biomaterials notably include calcium phosphates, such as hydroxyapatite (Ca10(PO4)6(OH)2) and tricalcium phosphate (Ca3(PO4)2), which are present in natural bones but are also used in the fabrication of components for the repair and reconstruction of damaged parts of the musculoskeletal system, but also due to their presence in 382,383 . Minerals and inorganic biomaterials contain several NMR-active isotopes, such as 1 H, 17 O, 19 F, 29 Si, 31 P, 27 Al and 43 Ca. Hence, solid-state NMR spectroscopy, including 2D correlation experiments, is largely employed to characterize atomic-level structures, and notably defects lacking long-range positional order, in minerals and biomaterials [376][377][378][379]384 .…”

“…Several reviews about homo-and hetero-nuclear recoupling sequences, mainly for spin-1/2 nuclei, have been published [33][34][35][36][37][38][39][40][41] . Through-bond correlation experiments, primarily for spin-1/2 isotopes in organic solids, 42,43 as well as correlation experiments for quadrupolar nuclei [44][45][46][47][48] have also been surveyed. Furthermore, through-bond and through-space correlation experiments for both spin-1/2 and quadrupolar nuclei were presented in reviews about solid-state NMR of a specific class of inorganic materials, including oxide glasses [49][50][51] , crystalline and amorphous aluminophosphates 52 , heterogeneous catalysts [53][54][55][56] , zeolites [57][58][59] and metal-organic frameworks 58,60 .…”