NMR properties

In order to do so, you will need to perform Hartree-Fock NMR calculations using the 6-311+G(2d,p) basis set. Compute the NMR properties at geometries optimized with the B3LYP method and the 6-31G(d) basis set. This is a recommended model for reliable NMR predictions by Cheeseman and coworkers. Note that NMR calculations typically benefit from an accurate geometry and a large basis set. 

In Exercise 3.5, we predicted the NMR properties of benzene and calculated the relative shift for the carbon atom with respect to TMS. In this exercise, we will compare those results with ones computed using other basis sets. 

Determine the effect of basis set on the predicted chemical shifts for benzene. Compute the NMR properties for both compounds at the B3LYP/6-31G(d) geometries we computed previously. Use the HF method for your NMR calculations, with whatever form(s) of the 6-31G basis set you deem appropriate. Compare your results to those of the HF/6-311+G(2d,p) job we ran in the earlier exercise. How does the basis set effect the accuracy of the computed chemical shift for benzene ... 

NBO population analysis 195 NBO program 196 Newman projections 290, 292 NewZMat utility xxxvii Windows xlvi nice command xxxviii nitrobenzene 165 NMR properties 21,29, 53, 104 Nobes 117 Norden 218 normal modes 65 normal termination message xlv nuclear displacements 65 numeric second derivatives 61 Nusair 119... 

Atomic charges and electrostatic potentials Vibrational frequencies IR and Raman spectra NMR properties... 

The hydrazines of quinoxaline aldehydes and ketones are so closely akin to regular hydrazinoquinoxalines that all are included in this section. The NMR properties of such hydrazine derivatives have been studied. ... 

In addition to the standard constraints introduced previously, structural constraints obtainable from the effects of the paramagnetic center(s) on the NMR properties of the nuclei of the protein can be used (24, 103). In iron-sulfur proteins, both nuclear relaxation rates and hyperfine shifts can be employed for this purpose. The paramagnetic enhancement of nuclear relaxation rates [Eqs. (1) and (2)] depends on the sixth power of the nucleus-metal distance (note that this is analogous to the case of NOEs, where there is a dependence on the sixth power of the nucleus-nucleus distance). It is thus possible to estimate such distances from nuclear relaxation rate measurements, which can be converted into upper (and lower) distance limits. When there is more than one metal ion, the individual contributions of all metal ions must be summed up (101, 104-108). If all the metal ions are equivalent (as in reduced HiPIPs), the global paramagnetic contribution to the 7th nuclear relaxation rate is given by... 

THF solution [290]. There had been much confusion in the past about the magnetic moment of the iron(I) species and the correct Mossbauer and NMR properties caused by impurities of the samples and possible unknown axial ligation. However, with clean crystallized samples with known molecular structure [291], the first reduction product of iron(II)(tetraphenylporyphrin), [Fe(TPP)], can be clearly characterized as a quasiplanar iron(I) complex with spin S = 1/2 (EPR = 2.28,... 

Y. Zhang, G. J. Hirasaki, W. V. House, R. Kobayashi 2002, Oil and Gas NMR Properties The Light and Heavy Ends, paper HHH prepared for the SPWLA 43rd Annual Logging Symposium, Osio, Japan, June 2—5, 2002. 

For example, despite the high symmetry of C60, no calculation of its NMR properties at the MP2 level has been reported so far. DFT-based methods, on the other hand, can readily be applied to this and to larger fullerenes, see Buhl et al., 1999. 

Extraframework cations are needed in anionic zeolites for charge balance, and for several zeolite topologies their locations are well investigated [281, 282]. Different cations have been investigated by solid state NMR in the past with different NMR properties and different project targets. We restrict this section to a tutorial example on sodium cation motion in sodalite and cancrinite structures [283-285], 23Na has a nuclear electric quadrupole moment, and quadrupolar interaction is useful to investigate jump processes, especially when they are well defined. 

The synthesis, X-ray structure, and dynamic NMR properties of the arachno 10-vertex cluster [9,9-(PMe2Ph)2-9,6,8-PtS2B7H7] has been reported the compound was fluxional via a vertex flip of the Pt(PMe2Ph)2 moiety.84... 

The real power of MRI is the ability to exploit the inherent NMR properties of different tissues and tissue pathologies. The main MR parameters are known as longitudinal-relaxation time-constant (Tl), describing the time for the magnetization to recover to its equilibrium along the main-field axis after RF perturbation transverse-relaxation time-constant (T2), describing the... 

The particular NMR properties of Pt caused an additional problem. Due to the presence of surfaces near most of the nuclei, the NMR line is very broad (approximately 4 kG wide). This means that only a small fraction of the nuclear spins can be excited by an rf pulse and thus contribute to any given NMR signal. Given these various constraints, our NMR studies of platinum catalysts required 1-gram samples containing 5-10% Pt by weight. 

In general, NMR properties of a molecule are tensor properties. That is, their value depends upon the spatial relationship of the molecule to the applied magnetic field. As such, each property can be described using three principal components, plus three angles to specify the orientation... 

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