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Abstract

The singlet oxygen generating efficiency of several thiophenic compounds, including oc-terthienyl (αT) and some of its synthetic analogues, has been determined using laser flash photolysis techniques. The method, which is based on the time-resolved bleaching of 1,3-diphenylisobenzofuran, led to relatively high efficiencies for all the substrates examined; for example the values were 0.86, 0.69 and 0.63 for αT, DBrαT and TNP, respectively in chloroform-d at 293K. Our results also indicate that high intersystem crossing efficiencies must be a common characteristic in these compounds. The variations in singlet oxygen yields were found to be modest in comparison with changes in the biological activity of these compounds, therefore suggesting that other factors are also quite important in determining the latter.