NQCC nuclear quadrupole coupling

Other key properties of these complexes relevant for comparison with experiment are the nuclear quadrupole coupling constants. Theoretical NQCC values, as calculated via electric field gradients, are discussed exhaustively in several recent theoretical investigations [26,28,30,33,34] and in experimental work [4-11]. BH HLYP/aug-cc-pVTZ calculated NQCCs [30,34], as evaluated for XY- -NH3 complexes, are listed in Table 10. 

Because the atoms occupy highly symmetric lattice positions, anisotropic parameters such as chemical shift anisotropy (CSA) or nuclear quadrupole coupling constants (NQCC) are either zero or fairly small. 

The calculated nuclear quadrupole coupling constants (NQCCs) of in artemisinin 9a and some of its derivatives and the effects of charge density due to the nature of ligands on the NQCC of were described. All calculations were performed at the HF/3-21G level <2005MI366>. 

It is important to note that for 0 the nuclear quadrupole coupling constant is also an important NMR parameter, which can be used to characterize both the identity of the tetrahedrally coordinated atoms, T, in a T-O-T linkage, and the value of the T-O-T angle. Earlier calculations (24) showed a decrease in the O NQCC as the Si-O-Si angle decreases, a trend verified by experiment (34, 35). Later calculations(36) indicating a progessive decrease in the O NQCC for Si-O-Si, Si-O-Al and Al-O-Al angles were also verified. 

Nuclear quadrupole coupling constants (NQCCs) constitute another window into the fundamental attributes of the hydrogen bonding phenomenon. Bacskay et al. decompose the NQCC, X, at a nucleus A of a H-bonded complex in terms of this same property in the unperturbed molecule, y, and its shift due to complexation, Ax-... 

The 14N quadrupole hyperfine structure was analyzed from the MW spectrum and the nitrogen nuclear quadrupole coupling constants (NQCC) for aniline-Hy are determined as follows xaa = 2.34, Xbb = 1-86 and Xcc = —4.20 MHz38. 

Relaxation and self-diffusion techniques in solution are widely used to study hydrogen-bonded systems. The nuclear quadrupole coupling constant (NQCC) presents a sensitive probe for the strength of hydrogen bonding. Unfortunately in the liquid phase this property cannot be measured in a direct way. Two new indirect methods are now presented for determining NQCC in H-bonded liquids. Ferris and Farrar showed that for the OD deuteron of ethanol the DQCC is related to the chemical shift of the hydroxy proton by a linear equation. Thus the straightforward measurement of the chemical shift... 

The 2 2-component of the EFG operator q is now to be determined by electronic structure theory either from relativistic or nonrelativis-tic wave functions. The expression e Qqzz in eq- (17) is the nuclear quadrupole coupling constant (NQCC) and can be obtained by experiment leading to the sought quadrupole moment eQ. Due to its dependence the EFG operator especially stresses the core region of the electronic wave function and relativity can be expected to play a major role. For the adequate treatment of heavy atoms and molecules containing heavy elements relativity is therefore indispensable and we will mention nonrelativistic results only for comparative purposes. Before we treat the subject of relativistic qzz calculations in detail a few common experimental techniques for accurate NQCC measurements are briefly discussed and the underlying physical principles mentioned. 

The nuclear quadrupole coupling constant (NQCC) is defined as -eQ V jh. The EFG at the nucleus affects the NMR relaxation processes, thus it is relevant in the analysis of the linewidths of NMR signals. The linewidth is proportional to the inverse relaxation time (Abragam 1961), that is ... 

The nuclear quadrupole coupling constant (NQCC) is a tensor quantity related to the efg tensor. In frequency units... 

The nuclear quadrupole coupling constants (NQCC), e Q (Chapter 2, Section 2.4) monitors the electric field gradient (efg) at the nuclear site, the largest component being given... 

Nuclear quadrupole coupling constants and asymmetry parameters [in brackets] are from single crystal studies. NQCC( Mn) values have also been predicted from partial quadrupole splitting parameters for [Mn(CO)5L] (L = CN, CNR, PPhj, NCS, N3, SbPhj, and and calculated from Wy2 of the NMR resonance for [MnH(CO)5 ... 

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