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 boolean AND N)] (X = -C C-R, N boolean AND 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 sigma-bonded alkynyl derivatives. The coordinated acetylene group induces a redshift of the lambda(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 boolean AND N)] (X = pyridine, H2O, N boolean AND N = bipy, phen).