Deuterium quadrupole coupling constants

A 3H and 2H NMR study of single crystals of [Ag(NH3)2][Ag(ONO)2] has been reported.32 Rapid reorientational motions of the ammine groups around their C3 axes were found. The orientations of the C3 axes within the crystal corresponded with the Ag—N bond directions of the [H3N—Ag—NH3]+ unit. The deuterium quadrupole coupling constant was determined and found to be identical to that of solid ND3. It was concluded that the electronic configuration and the geometric structure of ammonia were changed only very slightly upon coordination to silver ions. 

Further support for the non-centred enol hydrogen bond has come from 13C and 2H spin-lattice relaxation times of AA and 2H2AA from which deuterium quadrupole coupling constants are derived. These are explained in terms of a double minimum potential well67. These same workers also discuss the broadness of the <5(OHO) signal and conclude that it is due to bond lengthening rather than contributions from trans enol forms. The minimum line width for AA achieved by exhaustive drying was 0.5 Hz. 

The and N relaxation rates and the deuterium quadrupole coupling constant for pyrazine have been reported (1503) but the motion of this molecule could not be analyzed. N-H Spin coupiings in pyrazine methiodides have been determined (704). 

R. Eggenberger, S. Gerber, H. Huber, D. Searles, and M. Welker, Use of Molecular Dynamics Simulations with Ab Initio SCF Calculations for the Determination of the Deuterium Quadrupole Coupling Constant in Liquid Water and Bond Lengths in Ice, J. Comp. Chem., 14 (1993), 1553-1560. 

Nuclear magnetic resonance (NMR) is perhaps the simplest technique for obtaining deuterium quadrupole coupling constants in solids or in liquid crystalline solutions. In ordinary NMR experiments with a magnetic field Hq > 104 gauss, the nuclear quadrupole interaction [Eq. (6)1 for deuterium is much smaller than the Zeeman interaction and can be treated as a perturbation to the Hamiltonian... 

Deuterium quadrupole coupling constants can also be obtained from electron nuclear double resonance (ENDOR).19 30 An observation of the hyperfine structure caused by quadrupole coupling in the electron paramagnetic resonance (EPR) spectrum, as for many lanthanide complexes, has not been reported for deuterium. The determination of nuclear quadrupole coupling constants from Mossbauer spectroscopy is not applicable to the deuterium nucleus. 

Since the immediate electronic environment of the deuterium nucleus in most compounds is relatively simple, deuterium quadrupole coupling constants show very systematic variations with molecular structure. In covalent compounds, except those with hydrogen bonds or multicentered bonds (as in many boron deuterides), deuterium is bonded to only one atom. The bonding electrons have essentially cylindrical symmetry, and the only asymmetry in the electronic environment of deuterium comes from indirectly bonded atoms. Therefore, in many cases, 17 is very small 0.1). 

The deuterium quadrupole coupling constant bears an interesting relationship to the force constant (k = 32 Rtydz2, where W = electro-... 

TABLE 1 Deuterium Quadrupole Coupling Constants (in kilohertz) for Several Compounds in Different Phases... 

If the X atom in the X-D bond can have different forms of hybridization, the force constant and the deuterium quadrupole coupling constants vary accordingly. The trend sp3 < sp2 < sp for deuterocarbons has been established32 37,46 (Table 1). Non-electron-deficient boron deuterides behave similarly.62 A molecular orbital calculation37 showed that the change of the quadrupole coupling constant is mainly due to the shorten-... 

FIGURE 4 Deuterium quadrupole coupling constant of hydrogen-bonded crystals as a function of O—O distance. The circles are experimental values, with a line drawn to show the general trend. The triangles and squares are theoretical values for two different sets of O-D distances in a molecular orbital calculation.1 ... 

Phase transitions of ferroelectric materials8,39 can also be studied through the variation of the deuterium quadrupole coupling constant with temperature. 

More sophisticated basis sets have not been used extensively to study deuterium quadrupole coupling constants. Recently, however, L. C. 

Another parameter that may be very relevant to the structural characterization of polyhydrido complexes in both solution and sohd is the deuterium quadrupole coupling constant (CQ).47,74 78 Formation of a chemical bond creates a strong nonhomogeneous electric field along its direction (z axis) measurable by the electric... 

Table 3. Deuterium quadrupole coupling constants DQCC and bond ionicities i for...

Definitions the electric field gradient, the asymmetry parameter of the electric field gradient and the deuterium quadrupole coupling constant. 

DEFINITIONS-.THE ELECTRIC FIELD GRADIENT, THE ASYMMETRY PARAMETER OF THE ELECTRIC FIELD GRADIENT AND THE DEUTERIUM QUADRUPOLE COUPLING CONSTANT. 

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