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Copper complexes with non-innocent ligands: Probing CuII/catecholato-CuI/o-semiquinonato redox isomer equilibria with EPR spectroscopy

, , , and . Inorganica Chimica Acta, (2002)
DOI: 10.1016/S0020-1693(02)01081-2

Abstract

The temp.-dependent intramol. metal/ligand electron transfer equil. (L)CuII(Q2-).dblharw.(L)Cu1(Q·-) was quant. analyzed by EPR as a function of the noninnocent o-quinonoid ligand Q and of the co-ligand L. Suitable co-ligands were 1-methyl-(2-methylthiomethyl)-1H-benzimidazole and 1-diphenylphosphino-2-dimethylaminoethane (dde) which can tolerate both copper oxidn. states. EPR hyperfine data were extd. for a variety of alkyl- and methoxy-substituted o-semiquinones and their copper(I) complexes in soln. A close match of Q and Cu redox orbitals is essential for observing the redox isomer equil. which was similarly reported for aminoxidase enzymes. Efforts to isolate the mixed-ligand compds. from soln. failed due to coordination disproportionation. The new Cu(dde)2(ClO4) was structurally characterized with comparable Cu-N and Cu-P distances of 2.24-2.27 \AA and a P-Cu-P angle of 142.41(5)°, the 2+2 coordination pattern could be reproduced by DFT calcns. on SciFinder(R)

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