Metal nitroxyl interactions 39. electron electron spin spin splitting in the epr spectra of nitroxyl spin labeled manganese ii complexes in fluid solution

More, J. K.; More, K. M.; Eaton, G. R.; Eaton, S. S.

X-band and Q-band EPR spectra were obtained for a series of spin-labeled ligands coordinated to bis(hexafluoroacetylacetonato)manganese(II) and bis(trifluoroacetylacetonato)manganese(II) in fluid solution. Values of the exchange coupling constant, J, were obtained by computer simulation of the spectra and ranged from 14 .times. 10-4 to > 200 .times. 10-4 cm-1. Comparison of the values of J for these complexes with values obtained previously for the same ligands coordinated to VO(IV) indicate that J is about an order of magnitude smaller for Mn(II) which has S = 5/2 than for VO(IV) which has S = 1/2. The observation of spin-spin splitting indicates that the Mn(II) electron spin relaxation rate is slow relative to the magnitude of the spin-spin splitting.