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GagnC, Walton, et al. / X-ray PES of Copper(I) and Copper(II) ComplexesAbstract: The X-ray photoelectron spectra (X-ray PES) of pairs of mononuclear Cu(l1) and Cu(1) complexes of several macrocyclic ligands show that there is a chemical shift of -2.5 eV between the Cu 2p binding energies of these two oxidation states. A comparison of these data with that for mononuclear Cu(II1) complexes of biuret and the tetradentate tripeptide ligand derived from a-aminoisobutyric acid shows a shift of -2 eV between Cu(II1) and Cu(I1). These X-ray PES measurements do not support the alternative formulation of certain of the Cu(1) complexes as Cu(1l) or Cu(II1) species with reduced ligands. Thus a previous suggestion that Cu1(TAAB)(N03) is in reality [Cu"'(TAAB2-)](N03) is not in accord with the present X-ray PES results. The preceding information has been used in the analysis of the X-ray PES of binuclear copper complexes of the macrocycle (L) which is prepared by condensing 1,3-diaminopropane with 5-methyl-2-hydroxyisophthaldehyde. The oxidation-state formalism which has been used to describe the complexes Cu'CulL, [ C U W I~L ] C I O~, and [CuilCui(CO)L]-C104 is consistent with the observed Cu 2p binding energy spectra. However, the CuI1Cuii complex [ C U~~C U~~L ] ( C I O~)~.~H~O reveals some unexpected and novel features in its Cu 2p spectrum. The appearance of two sets of Cu 2~112,312 doublets is attributed to the X-ray induced one-electron reduction of -SO% of the Cu(I1)-Cu(I1) complex to a symmetrical delocalized species Cu(+l .S)-Cu(+l S) possessing Cu 2p binding energies which are intermediate between those of Cu(l1) and Cu(1). This novel species also displays a characteristic satellite structure. Similar behavior is exhibited by the chloride complex C U~~C U~~L C I~. 6H20, but with the mixed metal complex [ C U '~Z~~' L ] ( C I O~)~~H~O the one-electron reduction is believed to produce the dIo-dlo Cu(1)-Zn(1l) species.

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