An ever-growing energy demand is the result of the constant progress of our society. The sun as unlimited and free energy source might provide the energy necessary to satisfy the energy demand. One approach to harness sunlight relies on light-harvesting molecules, like it is done in green plants via photosynthesis.
Following the nature’s example, contemporary research efforts are devoted to mimic photosynthesis. In this effort solar energy is used to drive chemical reactions, such as in photoredox reactions. Therefore, we have developed homoleptic bis-4H-imidazolate-Cu(I) complexes with superb light absorption properties throughout the whole visible and into the NIR spectrum. Additionally, the title compounds exhibit three ligand-based reductions and one Cu(I) based oxidation, as has been revealed by cyclic voltammetry. The oxidation occurs at very low potentials reflecting the low energy metal to ligand charge transfer transition, which has been assumed from the UV/Vis data and has been supported by TD-DFT calculations. Through modification of the 4H-imidazoles electronically and sterically the properties of the resulting complexes can be modified, in terms of electrochemistry as well as UV/Vis absorption.
The exceptional redox activity as well as well as the intense absorption render these complexes promising candidates for photoredox reactions.