DETERMINATION OF THE HYPERFINE COUPLING WITH THE REMOTE NITROGEN IN THE VO2+-(IMIDAZOLE)4 COMPLEX BY ESEEM SPECTROSCOPY

Electron spin echo envelope modulation experiments are presented from N-15-substituted VO2+-(imidazole)4 complexes which demonstrate the interaction of the paramagnetic ion with the remote, weakly coupled ring nitrogen. The hyperfine parameters derived show that the interaction is about twenty times smaller than with the directly coordinated nitrogen of imidazole, a ratio comparable to that derived from known values for Cu2+-(imidazole)4. These findings question results reported from previous ENDOR work on VO2+-(imidazole)4.