Metal-nitroxyl interactions. 9. Electron-electron coupling in the copper complex (3-(N-(2,2,5,5-tetramethylpyrrolin-3-yl-1-oxy)amido)-4,10-dimethyl-5,9- diazatrideca-4,9-diene-2,12-dione)copper(II)

Resolved electron-electron coupling is observed in the room temperature solution EPR spectra of the spin labeled copper complex (3-(N-(2,2,5,5-tetramethylpyrrolin-3-yl-1-oxy)amido)-4,10-dimethyl-5,9- diazatrideca-4,9-diene-2,12-dione)copper(II), with values of the coupling constant ranging from 300 G in toluene solution to 415 G in pyridine solution. In most solvents an isomeric form of the complex is also observed which has a value of the electron-electron coupling constant of ∼2500 G. The fraction of the complex existing in the isomeric form varies from 2SO solution to ∼95% in toluene solution.