The fullerene structures of C20cage and bowl,C20H10 and their N-doped structures as C20cage NH,C20bowl NH, C20H10NH, C20H10N and their isomers are optimized using the MPW1PW91/6-31G level of the theory. Magnetic shielding tensors of 14N and 13C atoms are calculated by the same level of the theory. Results show that doping an N atom on fullerenes affects differently on the chemical shielding of ...

The model of Mason, Polnaszek, and Freed for ESR-slow-tumbling spectra is extended to the case of NMR line shapes for arbitrary tilt of the internal axis of relatively rapid rotation with respect to the principal axes of the chemical shielding tensor for a decoupled I = 1 / 2 nucleus. The theory is applied to an analysis of 31P NMR spectra from partially hydrated dipalmitoylphosphatidylcholine ...

Using NMR, we measure the proton chemical shift delta, of supercooled nanoconfined water in the temperature range 195 K < T < 350 K. Because delta is directly connected to the magnetic shielding tensor, we discuss the data in terms of the local hydrogen bond geometry and order. We argue that the derivative -( partial differential ln delta/ partial differentialT)(P) should behave roughly as the ...

A general method is presented for the reconstruction of interatomic vector orientations from nuclear magnetic resonance ~NMR! spectroscopic data of tensor interactions of rank 2, such as dipolar coupling and chemical shielding anisotropy interactions, in solids and partially aligned liquid-state systems. The method, called PRIMA, is based on a principal component analysis of the covariance matr...

The concept of covalency is widely used to describe the nature of intermolecular bonds, to explain their spectroscopic features and to rationalize their chemical behaviour. Unfortunately, the degree of covalency of an intermolecular bond cannot be directly measured in an experiment. Here we established a simple quantitative relationship between the calculated covalency of hydrogen bonds in liqu...

In this research, Quantum-mechanical calculations were performed at the HF method with the 6-31+G*basis set and at the B3LYP method with the 6-31+G* basis set in the gas phase and five solvents such as water, DMSO, methanol, ethanol and dichloromethane at six temperatures. According to these theoretical results of IR, we extracted thermo chemical parameters such as enthalpy (∆H Kcal/mol), Gibbs...

In this research, Quantum-mechanical calculations were performed at the HF method with the 6-31+G*basis set and at the B3LYP method with the 6-31+G* basis set in the gas phase and five solvents such as water, DMSO, methanol, ethanol and dichloromethane at six temperatures. According to these theoretical results of IR, we extracted thermo chemical parameters such as enthalpy (∆H Kcal/mol), Gibbs...

Recent ab initio calculations of cobalt NMR shielding show that DFT-GIAO calculations using hybrid functionals are found to reproduce experimental values well. This method is used to calculate the variation of the cobalt NMR shielding tensor of sqaure pyramidal nitrosyl complexes with respect to the CoNO geometry and to differing basal ligands. The isotropic shielding is shown to have a large n...

An n = π* interaction between neighboring carbonyl groups has been postulated to stabilize protein structures. Such an interaction would affect the (13)C chemical shielding of the carbonyl groups, whose paramagnetic component is dominated by n = π* and π = π* excitations. Model compound calculations indicate that both the interaction energetics and the chemical shielding of the carbonyl group a...

Cross-correlation between 15N-1H dipolar interactions and 1HN chemical shift anisotropy (CSA) gives rise to different relaxation rates of the doublet components of 1H-{15N} peptide backbone amides. Two schemes for quantitative measurement of this effect are described and demonstrated for samples of uniformly 15N-enriched ubiquitin and perdeuterated 15N-enriched HIV-1 protease. The degree of rel...