C. P. Cheng

Nitrogen-14 nuclear quadrupole resonance spectra of substituted nitrobenzenes

Abstract The 14 N nuclear quadrupole resonance spectra have been measured for nitrobenzene and nine substituted nitrobenzenes. The experiments were carried out at 77 K, using the double-resonance, level-crossing technique. The 14 N signals for the −NH 2 groups of m -and p -nitroaniline were also observed. The quadrupole coupling constants for the nitro group nitrogens vary from 1493 kHz for p -nitroaniline (η = 0.292) to 1232 kHz for m -dinitrobenzene (η = 0.360). The dependence of e 2 Qq / h upon the meta or the para substituent suggests that the substituents affect mainly the covalency in the nitrogen-carbon σ bond. A linear relationship is observed between e 2 Qq / h and the Hammett substituent constants.

Determination of the ratio of the nuclear electric quadrupole moments of 97Mo and 95Mo by nuclear quadrupole double resonance spectroscopy of Mo(CO)5P(C6H5)3 and CIS-Mo(CO)4[P(C6H5)3]2

Abstract Nuclear quadrupole double resonance techniques have been used to investigate the NQR spectra of two compounds Mo(CO) 5 P(C 6 H 5 ) 3 and cis-Mo(CO) 4 [P(C 6 H 5 ) 3 ] 2 . Nuclear resonances for 95 Mo and 97 Mo were observed for the first time and the absolute value of the ratio of the nuclear electric quadropole moments was determined to be 11.466 ± 0.042.

Oxygen-17 nuclear quadrupole double resonance spectroscopy

The Slusher–Hahn technique for detection of nuclear quadrupole transitions of low abundance spins at zero magnetic field is briefly described. Factors affecting the observed line shapes are discussed. The 17O n.q.r. spectra for a variety of substances studied at 77 K are presented. The results for several compounds are discussed in terms of the Townes–Dailey model, which leads to an assignment of oxygen 2p orbital populations.

14 N nuclear quadrupole resonance spectra of Co-ordinated thiocyanate

The 14N n.q.r. spectra have been measured for N- and S-bonded thiocyanates as ligands in several PdII complexes and a NiII complex; this technique sharply distinguishes between the two modes of bonding.