P-31 HYPERFINE INTERACTION IN A NEW TYPE OF PHOSPHORUS-CONTAINING IMINOXY FREE-RADICALS - AN ESR STUDY

Iminoxy radicals of a new type, having the general formula RC(= NO.)P(O)(OEt)2, were synthesized and characterized by means of ESR spectroscopy. The presence of two isomers due to the different position of the C = NO. fragment with respect to the R substituent and the P atom, and the relative stability of the isomers, was established. The influence of the R substituent on the relative population of the isomers was found. The nitrogen hyperfine constants for the isomers differ by about 10%, while the phosphorus hyperfine constant for the less populated isomer is about six time greater, reaching a value of 60 G. A linear correlation was found between the values of this hyperfine constant and Dimroth-Reichardt E(T)(30) solvent parameters. The solvent dependence of the P-31 hyperfine constant was shown to be stronger than the dependence found for the N-14 hyperfine constant of nitroxides and iminoxyls.