Nitrogen-14 and oxygen-17 hyperfine interactions in perturbed nitroxides Academic Article uri icon

abstract

  • We have measured the isotropic and anisotropic hyperfine splittings for di-tert-butyl nitroxide (DTBN) and 2,2,6,6-tetramethylpiperidine N-oxyl (TMPN) perturbed by molecular complex formation, by hydrogen bonding, and by solvent effects in aprotic solvents. We use these measurements to obtain the σ-π interaction parameters for a Karplus-Fraenkel equation (a1 = Q11iρiπ + Qjjiρjπ) which relates the 14N and 17O isotropic hyperfine splittings to the spin density in the nitroxide N-O π-electron system; QNNN = 23.9 ± 1.0 G, QOON = 3.6 ± 0.4 G, QOOO = 31.7 ± 0.7 G, and QNNO = 4.7 ± 0.5 G. In addition for protonated nitroxides QOON = 13.2 ± 0.3 G. The values of QNNN for TMPN and DTBN are identical and discussion of the angle dependence of the parameter suggests that the radicals in solution do not differ with respect to planarity at nitrogen.

author list (cited authors)

  • Cohen, A. H., & Hoffman, B. M.

citation count

  • 31

publication date

  • June 1974