SYNTHESIS AND MULTINUCLEAR NMR RELAXATION STUDY OF 2-PHENYLDIAZENE-1-CARBONITRILE 2-OXIDE AND ITS [N-15]-LABELED ISOTOPOMERS

[N-15]-2-Phenyldiazene-1-carbonitrile 2-oxide has been synthesized using nitrosobenzene and [N-15]-NH2CN and fully characterized by mass spectrometry and IR, C-13 and N-15 NMR spectroscopy. C-13 and N-15 spin-lattice relaxation times were measured and are discussed in terms of two main relaxation mechanism: dipole-dipole (DD) and chemical-shift anisotropy (CSA). Quantitative evaluation of the two contributions was achieved by measuring the nuclear Overhauser effect (NOE) and by performing experiments at different magnetic-field strengths (4.7, 6.3 and 9.4 T). The availability of N-15 selectively-labelled isotopomers provided a simple method to estimate, from C-13-T1 data, C-N bond distances. Motional parameters for isotropic molecular motion and phenyl internal rotation were calculated from relaxation data for the protonated ring carbons.