Photosensitizing Properties of Alkynylrhenium(I) Complexes [Re(–C≡C–R)­(CO) 3 (N∩N)] (N∩N = 2,2′‐bipy, phen) for H 2 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, H 2 formation was observed for all alkynyl complexes in the presence of a water‐reducing catalyst (WRC) and a sacrificial electron donor. Relative rates of H 2 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 λ max of the MLCT band in UV/Vis spectroscopy as compared to those of the corresponding halides, nitriles, or cationic Re I complexes, such as [ fac ‐ReX(CO) 3 (N∩N)] (X = pyridine, H 2 O, N∩N = bipy, phen).