Light-driven Charging of a Molecular Cu(I) Complex for Storage of Photoredox Equivalents and Discharging in the Dark

The diurnal day/night cycle presently is a great challenge for the harvest of solar energy rendering suitable energy storage schemes inevitable. In the described experiments a Cu(I) 4H-imidazolate complex is efficiently photoreduced in the presence of a sacrificial donor. The obtained two-electron reduced species is stored for more than 14 hours in the dark. In a dark reaction, the stored photoredox equivalents can be transferred to an electron acceptor while the starting Cu(I) complex is almost completely regained. Repetition of the photoreduction/reoxidation revealed a photoreduction efficiency of 72% after four cycles.