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Electrochemical techniques were employed to study electron transfer properties of a binuclear copper-macrocyclic ligand complex and to prepare several reduced derivatives. The complex, Cu"Cu"L(C104)2-2H20, was prepared by condensing 1,3-diaminopropane with 5-methyl-2-hydroxyisophthalaldehyde and CuíClCLL-óLLO. The Cu"Cu" complex was reduced in successive, quasi-reversible, one-electron steps at -0.52 and -0.91 V vs. NHE. Constant-potential electrolysis was employed to prepare the reduced species, CuI,CuIL(C104) and Cu'Cu'L, both of which were isolated and fully characterized. The mixed-valence species, Cu"Cu'L+, is stable in oxygen-free solutions (conproportionation constant: 3.97 X 106) and reacts with carbon monoxide to form an adduct, Cu"Cu'L(CO)C1C>4. The diamagnetic Cu'Cu'L species was obtained as essentially insoluble black needles which, however, formed a soluble dicarbonyl adduct, Cu'Cu'L(CO)2, on exposure to CO. The latter complex was not isolated. At the ambient temperature Cu"Cu'L+ exhibits an isotropic seven-line solution EPR spectrum while an anisotropic pattern was observed in frozen solutions (77 K), with four lines for g|| and unresolved g±. Variable-tempera ture experiments indicated coalescence at about 200 K suggesting an intramolecular electron transfer rate of about 1.7 X 10'°s_l at 298 K. Electronic absorption spectral measurements revealed at least two absorptions for Cu"Cu'L(C104)2 at 1700 and 1200 nm (CH2CI2), which are not present in Cu"Cu"L(C1C>4)2-2H20, Cu'Cu'L, or the carbonyl derivatives. The new spectral bands may be attributable to intramolecular electron transfer processes.

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