Previous work in our lab has shown that the N,N′-di-alkyl-2,11-diaza[3.3](2,6)pyridinophane (RN4) ligand system can stabilize uncommon oxidation states of late transition metals including Cu. To further probe the role of axial ligation and the presence of additional atom donors on the stability of Cu in different oxidation states, we have replaced the alkyl N-substituents with 2-methyl-pyridine (picolyl) to generate the symmetric and asymmetric ligands PicN4 and PicMeN4, respectively. Interestingly, we have shown that both PicN4 and PicMeN4 favors the formation of isolable CuII and CuI complexes. Cyclic voltammetry experiments show the presence of reversible CuI/II redox couples in both systems. We propose that this stability and reversibility is due to the binding preferences of the CuII and CuI metal centers within in each of the two flexible multidentate ligand systems. Determination of self-exchange rate constants for the PicN4Cu complexes further supports a biomimetic Cu site that can undergo rapid oxidation and reduction.

Pentadentate and hexadentate pyridinophane ligands support reversible Cu(I)/Cu(II) redox couples

253rd National Meeting (2017)

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