482583-33-5Relevant academic research and scientific papers
Copper complexes with non-innocent ligands: Probing CuII/catecholato-CuI/o-semiquinonato redox isomer equilibria with EPR spectroscopy
Kaim, Wolfgang,Wanner, Matthias,Kn?dler, Axel,Záli?, Stanislav
, p. 163 - 172 (2008/10/08)
The temperature-dependent intramolecular metal/ligand electron transfer equilibrium (L)CuII(Q2-)?(L)CuI(Q ·-) has been quantitatively analyzed by EPR as a function of the non-innocent 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 oxidation states. EPR hyperfine data were extracted for a variety of alkyl- and methoxy-substituted o-semiquinones and their copper(I) complexes in solution. A close match of Q and Cu redox orbitals is essential for observing the redox isomer equilibrium which has been similarly reported for aminoxidase enzymes. Efforts to isolate the mixed-ligand compounds from solution 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 A? and a P-Cu-P angle of 142.41(5)°, the '2+2' coordination pattern could be reproduced by DFT calculations.
