Nuclear quadrupole resonance of amidinium tetrachlorophosphorates

The³⁵C1 NQR spectra and relaxation parameters of the cyclic amidinium tetrachlorophos-phorates PCl₄(NCH₃)₂CX, where X=C₆H₅ (1), CCl₃ (2), and CF₃ (3), have been studied at 77 °K. The crystal of (3) has been found to contain two coexisting phases of the compound, which consist, respectively, of zwitterionic molecules of a hexacoordinated phosphorus atom with square-pyramidal symmetry of the PCl₄ group and molecules of chlorotropic isomers with a trigonal-bipyramidal environment for the phosphorus atom. The structural features of the crystalline state and the nature of the phosphorus—ligand bonds have been discussed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 6, pp. 727–730, November–December, 1985.     

Nuclear quadrupole resonance in 2,4-dinitrochlorobenzene

A study of the spin lattice relaxation (T₁) and the nuclear quadrupole resonance frequency (ν_Q) gives an important information about the dynamics of molecular groups in molecular solids. In the present paper, we analyze the contributions of the reorientational motion of nitro groups of 2,4-dinitrochlorobenzene to the NQR parameters of the chlorine nucleus in the molecule.

We found two contributions to T₁ and ν_Q due to the onset of the reorientation of nitro groups in the molecule; one of these contributions is mostly due to intermolecular effects in the crystal. For the chlorine nuclei, the efficiency of the modulation mechanism is usually provided by the change of the electric field gradient due to the moving molecular group; this gives us a way of how to assign each contribution to T₁ from the ortho and para positions of the NO₂ groups in the molecule. It is observed that there are two different potential barriers depending on the position of the nitro groups in the molecule. The behavior in the temperature dependence of the line width shows a thermal history dependence of the molecular crystal.     

Nuclear quadrupole resonance of mixed-valence charge-ordered dimers

The influence of an external magnetic field on the conditions of charge ordering of mixed-valence dimer clusters Ni²⁺–Ni⁺ is considered. The manifestations of charge ordering in the spectra of nuclear quadrupole resonance are elucidated. These spectra are shown to give information on the key parameters of charge-ordered crystals.     

Nuclear quadrupole resonance in organosilicon nitrogen compounds

Conclusions Based on the¹⁴N NQR data, the p – d interaction in dimethylaminosilanes is weaker than in the amides of phosphorus acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2331–2333, October, 1975.     

Nuclear quadrupole resonance in heteroorganic compounds of group III

Theoretical and Experimental Chemistry -