SINGLET OXYGEN PRODUCTION FROM EXCITED SINGLET AND TRIPLET-STATES OF ANTHRACENE-DERIVATIVES IN ACETONITRILE

The efficiencies of singlet oxygen production from the singlet and tri plet states of a series of anthracene derivatives in acetonitrile are reported. For anthracene and for all of the anthracene meso derivative s studied, the efficiency of singlet oxygen production from triplet st ates quenched by oxygen, f(Delta)(T), is found to be unity, with the e xception of 9-methoxyanthracene, where the value drops to one-third. T he efficiencies of singlet oxygen production from excited singlet stat es quenched by oxygen, f(Delta)(S), in acetonitrile as solvent, are lo wer than in cyclohexane and vary from zero to one-half. In addition, t he fractions of singlet states quenched by oxygen which yield triplet states, with or without singlet oxygen production, f(T)(O2), for anthr acene and 9-methyl-, 9-phenyl and 9,10-dichloroanthracene were measure d and the values were found to vary from 0.57 to 0.83. Kinetic conside rations allow the determination of estimates of this fraction for the other derivatives. For anthracene derivatives, when dissolved in cyclo hexane, all the values obtained for f(T)(O2) are unity whereas when di ssolved in acetonitrile, f(T)(O2) values were found to be lower than u nity except in the case of 9,10-dicyanoanthracene, which is unity in b oth solvents.