Single oxygen generation sensitized by spiro(dipyridinogermole)(dithienogermole)s

Three spiro(dipyridinogermole)(dithienogermole) derivatives ( 1-3 ), including newly prepared spiro(dipyridinogermole)[di(2-pyridyl)dithienogermole] ( 3 ), were examined as photosensitizers for singlet oxygen ( 1 O 2 ) generation in dichloromethane-methanol. Irradiation of their air-saturated solutions led to the generation of 1 O 2 , which was readily trapped by well-known scavengers, dihydronaphthoquinone (DHN) and diphenylisobenzofuran (DPBF). Spiro(dipyridinogermole)[bis( n -hexylbithiophenyl)dithienogermole] ( 2 ) showed the best performance with a first-order rate constant that was higher than that of tetraphenylporphyrin (TPP), an efficient photosensitizer for 1 O 2 generation. This is ascribable to the efficient intersystem crossing characteristic of the dipyridinogermole unit. The quantum yield of 1 O 2 generation was Δ = 0.72 for 2 , relative to that for rose bengal (RB) in methanol as reference ( Δ = 0.8). Three spiro(dipyridinogermole)(dithienogermole) derivatives ( 1-3 ), including newly prepared spiro(dipyridinogermole)[di(2-pyridyl)dithienogermole] ( 3 ), were examined as photosensitizers for singlet oxygen ( 1 O 2 ) generation in dichloromethane-methanol.