A novel propagator approach for NMR signal attenuation due to anisotropic diffusion is proposed, with consid-eration of the loss of spin phase memory during random motion. This method is applied to explicitly investigate free diffusion, restricted diffusion between two parallel plates, and diffusions under different nonlinear gradients, including an n-order nonlinear field and gradient with a cosine distribution. The method provides an intuitive physical picture and simplifies the treatment with the effects of finite-width gradient pulses in restricted diffusion and with nonlinear gra-dients. Theoretical results are in good agreement with those of previous reports.

The 19F NMR chemical shieldings of solid-state alkaline-earth-metal fluorides MF2 (M) Be, Mg, Ca, Sr, Ba) and alkali-metal fluorides MF (M) Li, Na, K, Rb, Cs) were systematically studied by the gaugeindependent atomic orbital (GIAO) method at the level of density functional theory (DFT). The 6-311+G(d) basis set was used for the inspected fluoride ion. The performance of the effective core potentials (ECP) of LanL2DZ and CRENBL basis sets for metal atoms were compared to 3-21G all-electron basis set. The role of d polarization functions for metal atoms is investigated. The results show that the clusters [FMg3F9]4-, [FM4F6]+ (M) Ca, Sr, Ba), and [FM6]5+ (M) Li, Na, K, Rb, Cs) used to model the bulk solids are reasonable. The electrons in the next outermost shell of metal atoms have significant influence on the 19F NMR calculations and should be treated as valence electrons together with the electrons in the outermost shell, while the remaining electrons can be represented by the ECP of CRENBL basis set. When the CRENBL basis set (with ECP for core electrons) supplemented with two sets of d polarization functions was used for the metal atoms, the approach of locally dense basis sets can be used to successfully reproduce the 19F shielding values. Since only the inspected resonant fluorine atom needs a high-grade all-electron basis set, it is a relatively inexpensive means of obtaining reliable shielding properties for the inspected species. In addition, the different exchangecorrelation functional implemented in hybrid DFT method has a minor influence on the calculated shielding. Although all the calculated results are somewhat overestimated, the correlation coefficients and the slopes of the fitting lines between the theoretical predictions and experimental observations are close to unity, indicating the good agreement of the theoretical results to the experimental values.

Optimal RF flip angles of the NMR CRAZED pulse sequence for multiple spin-echoes (MSEs) and intermolecular multiple quantum coherences (iMQCs) of different orders were investigated theoretically and experimentally. An an-alytical expression for the dependence of signal intensities on RF pulse flip angles was derived for the cases when higher-order expansion terms of Bessel functions can be neglected from a combination of dipolar demagnetizing field treatment and product operator formalism. Theoretical predictions for both the relative signal intensities and the optimal flip angles at which the signal intensities are maximized are found to be in excellent agreement with experimental re-sults.

To simulate the types of coordination and solution structures of the active site of haloperoxidases, the interaction systems between diperoxovanadate complexes [OV(O2)2L]n-(n=1 or 3, L=oxalate or H2O) and a series of histidine-like ligands in solution have been studied by using 1D multinuclear (1H, 13C, and 51V) NMR, 2D diffusion ordered spectroscopy, and variable-temperature NMR in 0.15 mol/L NaCl ionic medium, representing the physiological conditions of human blood. Some direct NMR data are given for the first time. The reactivity among the histidinelike ligands is imidazole>2-methylimidazole>carnosine≈4-methylimidazole>histidine. Competitive coordinationinteractions result in a series of new peroxovanadate species [OV(O2)2L']- (L'=histidine-like ligands). When theligands are 4-methylimidazole, histidine, and carnosine, a pair of isomers have been observed, which are attributedto different types of coordination between vanadium atom and ligands. The results of density functional theorycalculations provided a reasonable explanation on the relative reactivity of the histidine-like ligands and the molarratios of isomers. Theoretical results signify the importance of the solvation effect for the reactivity and stability of the interaction systems.