Synthesis and multinuclear NMR relaxation study of 2-phenyldiazene-1-carbonitrile 2-oxide and its [15N]-labelled isotopomers
Abstract
[15N]-2-Phenyldiazene-1-carbonitrile 2-oxide has been synthesized using nitrosobenzene and [15N]-NH2CN and fully characterized by mass spectrometry and IR, 13C and 15N NMR spectroscopy. 13C and 15N spin–lattice relaxation times were measured and are discussed in terms of two main relaxation mechanisms: 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 15N selectively-labelled isotopomers provided a simple method to estimate, from 13C–T, 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.