Design and photophysical studies of iridium(iii)-cobalt(iii) dyads and their application for dihydrogen photo-evolution

We report several new dyads constituted of cationic iridium(iii) photosensitizers and cobalt(iii) catalyst connected via free pendant pyridine on the photosensitizers. These dyads were studied by X-ray crystallography, electrochemistry, absorption and emission spectroscopy as well as theoretical calculations and were shown to efficiently produce H-2 under visible light irradiation. In every case, the dyad outperformed the equivalent system without a pendant pyridine. The dependence between irradiation wavelength and photocatalytic performances was also studied, with H-2 being evolved with turn-over numbers up to 295, 251, 188 and 78 mol(H2) mol(PS)(-1) under blue, green, yellow and red light, respectively.