The principal (13)C chemical-shift values for the pi-[TCNE](2)(2-) dimer anion within an array of counterions have been measured to understand better the electronic structure of these atypical chemical species in several related TCNE-based structures. The structure of pi-[TCNE](2)(2-) is unusual as it contains two very long C-C bond lengths (ca. 2.9 Angstroms) between the two monomeric units an...

A recently developed methodology for calculating, analyzing, and visualizing nuclear magnetic shielding densities is used studying spatial contributions including ring-current to 1H resonance (NMR) chemical shifts of aromatic anti-aromatic free-base porphyrinoids. Our approach allows a visual inspection the origin positive (shielding) negative (deshielding) constants. Diatropic paratropic curre...

The effect of rotation and vibration on the nuclear magnetic resonance ~NMR! shielding constants was computed for HF, F2, N2, CO, and HBr. The shielding constants for H, C, N, O, and F nuclei were calculated using sum-over-states density functional perturbation theory ~SOS-DFPT!. Diatomic ro-vibrational states were calculated from a discrete variable representation using Morse potentials and po...

The nuclear magnetic resonance (NMR) parameters in porphyrin and porphycene have been calculated to investigate their changes during the process of proton exchange, using density-functional theory (DFT) for both the spin-spin coupling constants and the shielding constants. In addition, in calculations on the smaller 1,3-bis(arylimino)isoindoline molecule, we have tested the performance of our c...

Sulforaphane, an isothiocyanate found in broccoli and other cruciferous vegetables. it is an antioxidantand anti-cancer agent, and reduces blood pressure, and also has anti-allergic Effects.In this article, six theoretical methods have been used for calculation of physical parameters insolforaphane and several similar compounds. We calculated physical parameters like atomic charges.energy (AE) ...

A series of four anhydrous group 13 chloride salts has been studied by (35/37)Cl solid-state NMR spectroscopy and complementary quantum chemical calculations. Due to the large (35/37)Cl quadrupolar interactions in these salts, a high magnetic field (21.1 T) and the variable-offset QCPMG technique was used to obtain full chlorine central transition (m = -1/2 <--> 1/2) NMR spectra. Analyses of th...

Nuclear magnetic shielding is a second-order molecular electronic property which provides a severe test of the accuracy of molecular quantum mechanical calculations. While electric dipole polarizability and hyperpolarizabilities provide tests of the wavefunction at the outer regions, nuclear shielding is very sensitive, especially to contributions from high angular momentum functions, in the re...

We introduce a new solid-state NMR method, which uses very slow sample rotation to visualize NMR spectra whose width exceeds feasible spectrometer bandwidths. It is based on the idea that if we reorient a tensor by a known angle about a known axis, the shifts in the NMR frequencies observed across the spectral width allow us to reconstruct the entire tensor. Called STREAQI (Slow Turning Reveals...

A new method for relativistically corrected nuclear magnetic resonance ~NMR! chemical shifts is developed by combining the individual gauge for the localized orbital approach for density functional theory with the normalized elimination of a small component using an effective potential. The new method is used for the calculation of the NMR chemical shifts of Mo and W in various molybdenum and t...

Precise theoretical predictions of NMR parameters are helpful for the spectroscopic identification of complicated biological molecules, especially for the carbon shielding tensors in amino acids. The (13)C shielding tensors of various crystalline amino acids and peptides have been calculated using the gauge-including projector augmented wave (GIPAW) method based on two different periodic struct...