High-resolution carbon-13 solid-state nuclear magnetic resonance: Decoupling and recoupling under high-speed magic angle spinning

The interference effect between rapid MAS and CW RF fields known as rotary resonance, can make the modulated heteronuclear dipolar coupling or CSA appear to be static. This thesis will demonstrate that this interference effect can be used to measure the heteronuclear dipolar couplings in isolated spin pairs that are averaged by MAS. It will also be shown that RF decoupling and spinlocking field strengths must be at least 8 times the spinning speed to avoid any interference with MAS. This means that when MAS speeds of 30 kHz are used, RF field strengths of at least 240 kHz are required.;This work will also demonstrate that the combination of fast MAS and high-power TPPM decoupling allow the observation of the 13C- 13C J couplings in uniformly labeled molecules. The resolution obtained in the solid state NMR spectra is very close to that found in the liquid state. However, as the spinning speed increases, the temperature also increases, which is reflected in the sucrose spectra, as the chemical shifts of solid-state sucrose are temperature dependent. From the initial examination presented in this thesis, it appears that the 1JCC couplings are temperature independent. In fact it will be shown that the J couplings in solid-state sucrose appear to be very similar to those measured in the liquid state, including the trans-glycosidic couplings 3J C1C1', 2JC1C2' and 3JC2C2'. It will also be demonstrated that 2D COSY and INADEQUATE solution state experiments can be applied to uniformly 13C labeled molecules in the solid-state and that it is not necessary to have resolved J couplings in order to obtain solid-state INADEQUATE spectra of uniformly labeled compounds.;Finally it will be illustrated that with the proper phase cycling, artifacts can be removed from the 2D RFDR experiments. It also appears that there is a significant through-bond relay contribution to the RFDR magnetization exchange rate. As a result, in order to obtain accurate internuclear distances from the RFDR experiment of a multiply labeled molecule, an exact quantum mechanical simulation is required.