Singlet oxygen quantum yields of different photosensitizers in polar solvents and micellar solutions

The singlet oxygen luminescence method and the photochemical methods using 1,3-diphenylisobenzofuran (DPBF) or bilirubin ditaurate (BDT) as chemical q uenchers were employed to determine the single oxygen quantum yields (Phi(D elta)) of different phthalocyanines and tris(2,2'-bipyridyl)ruthenium(II) d ichloride in dimethylformamide (DMF) or aqueous micellar solution of 0.1 M CTAC (cetyltrimethylammonium chloride). Additionally, a perylenetetracarbox ylic acid diimide derivative was examined in DMF. In a series of tetrasulfo nated phthalocyanines (PTS) the following order was found: ZnPTS > GaPTS > AIPTS approximate to H2PTS > CoPTS. In general, he singlet oxygen quantum y ields are higher in DMF than in 0.1 M CTAC/H2O. The results obtained with t he photochemical systems are comparable with those obtained by the photophy sical method. The photochemical DPBF method results in absolute values of Phi(Delta). How ever, in micellar solution, chain reactions occur when DPBF is used as chem ical quencher in the photo-oxidative process. This problem can be overcome by adding sodium thiosulphate which is able to destroy the endoperoxide ini tially formed. BDT can be used as quencher in different solvents to determi ne Phi(Delta) relative to a photosensitizer with known singlet oxygen quant um yield in the respective solvent. In comparison to the chemical methods the luminescence method exhibits the advantage that side reactions of the quencher are excluded. But normally th e Phi(Delta) values obtained are relative to a reference, since absolute de terminations need much larger efforts. (C) 1998 John Wiley & Sons, Ltd.