Nuclear quadrupole resonance of In115, Br79, and Br81 in the compounds InOCl,InOBr, InOF

Russian Chemical Bulletin -     

Structural analysis of some chlorinated pesticides by nuclear quadrupole resonance spectrometry

Nuclear Quadrupole Resonance (NQR) spectrometry provides a useful technique for the determination of structure and has been employed to demonstrate the difference in the chemical environment of the (35)Cl atoms in several chlorinated organic compounds commonly used as pesticides. A tentative assignment of signals to specific chlorine atoms has been made, by utilizing spectra-structure correlation charts, in 1,2,3,4,10,10-hexachloro-6,7-epoxy-1,4,4a,5,6,7,8.8a-octahydro-1,4-endo,endo-5,8-dimethanonaphthalene (Endrin) and in two isomers of 6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin-3-oxide (Endosulfan alpha and beta).     

Line broadening effects in nuclear quadrupole resonance

The major broadening mechanism in Nuclear Quadrupole Resonance is the spread in the electric field gradient produced by crystal defects. In multilevel spin systems, the frequencies of the various possible resonances are different functions of the components of the electric field gradient. This paper examines the role of both the principal component of the field gradient and the asymmetry component in the relationship between the linewidths of the two resonances of I = $\text{5}\text{2}$ nuclei. Comparison with experimental data shows various ways in which defects interact with quadrupolar nuclei.     

14N nuclear quadrupole resonance in carbazoles

Nitrogen-14 nuclear quadrupole resonance frequencies at 77 K are reported for a series of carbazole compounds including N-vinylcarbazole. Differences in charge distribution between pyrrole and carbazole are explained on the basis of delocalization of pi electrons. Effects of the aldehyde and vinyl groups on charge distribution are discussed. Sigma bond polarization between the pyrrole nitrogen and the nitroso nitrogen toward the pyrrole nitrogen exists in N-nitrosocarbazole.     

Chlorine nuclear quadrupole resonance transition frequency in p-chloroaniline

The Nuclear Quadrupole Resonance transition frequency of Cl in p-chloroaniline has been measured as a function of temperature in the range 80–300 K. Its temperature dependence is analyzed using Bayer's theory in the quasi-harmonic approximation and including the internal modes contribution. Excellent agreement is found with Raman and IR data. Also, the importance of the internal modes is clearly shown. The N transition frequency data are analyzed, and in order to produce good agreement with previous work a simple model to account for the electric field gradient at the N nuclear site had to be proposed.