New publication in Chem. Sci. online

Manipulating electron transfer – the influence of substituents on novel copper guanidine quinolinyl complexes

Type 1 copper proteins, which are also called blue copper proteins, are responsible in nature for electron transfer processes in all living organisms. The fast electron transfer is made possible by the entatic state in which the type-1 copper proteins are found. In previous work of the Herres-Pawlis group, it was shown that copper guanidine quinoline complexes are highly suitable as model complexes for the entatic state of the electron transfer of type 1 copper proteins. This suitability is caused by their special structural properties. The copper complexes exhibit a highly distorted structure, which is strongly determined by the donor properties of the guanidine quinoline ligand. As a result, the associated copper(I) and copper(II) complexes of the redox pairs show a high structural resemblance. The special electron transfer properties of the copper-guanidine-quinoline complexes are described by the electron self-exchange rate.

In this publication, guanidine quinoline ligands with different substituents were synthesized to gain a deeper understanding of the electron transfer properties and how to affect and enhance them. Therefore, the copper complexes were characterized and analyzed in detail using a variety of methods. The influences of the substituents on the structures of the copper complexes were investigated experimentally using XRD and XAS measurements as well as DFT calculations. In addition, the influences of the substituents on the donor properties of the ligands in the complexes were determined by NBO calculations. The electrochemical properties were characterized by cyclic voltammetry and related to the influences of the substituents on the complex structures and donor properties of the ligands. Using Markus theory, the electron self-exchange rates of the complexes were determined performing stopped-flow UV/Vis measurements. In this work, different substituents were revealed to be suitable for manipulating and enhancing the electron transfer properties of the complexes significantly for different reasons. The results were correlated with the influences of the substituents by DFT-calculations of the reorganization energies.

The article Manipulating electron transfer – the influence of substituents on novel copper guanidine quinolinyl complexesis available on the webpage of the publisher.