Photosensitizing Properties of Alkynylrhenium(I) Complexes [Re(–C≡C–R)­(CO)3(N∩N)] (N∩N = 2,2′-bipy, phen) for H2 Production



A series of complexes of the type [fac-Re(X)(CO)3(N∩N)] (X = –C≡C–R, N∩N = 2,2′-bipy, 2,2′-phen) were synthesized and fully characterized. Their photophysical characteristics make them very convenient photosensitizers (PSs). Upon light irradiation, H2 formation was observed for all alkynyl complexes in the presence of a water-reducing catalyst (WRC) and a sacrificial electron donor. Relative rates of H2 production indicate a dependency upon the diimine ligands rather than upon the nature of the σ-bonded alkynyl derivatives. The coordinated acetylene group induces a redshift of the λmax of the MLCT band in UV/Vis spectroscopy as compared to those of the corresponding halides, nitriles, or cationic ReI complexes, such as [fac-ReX(CO)3(N∩N)] (X = pyridine, H2O, N∩N = bipy, phen).