Photochemistry of 9,10-anthraquinone-2,6-disulphonate

Abstract

The photochemistry of 9,10-anthraquinone-2,6-disulphonate has been studied by observation of the transient emission and absorption following nanosecond laser excitation. Spectra and kinetics are reported for five different transient species: the triplet, the semiquinone radical anion and neutral radical, and two complexes formed by reaction of the triplet with water. Despite problems due to spectral overlap and the presence of up to three transients at the same time following excitation, spectra assignable to each species have been obtained by suitable choice of the chemical conditions. A study is presented of the effect of pH and anthraquinone and oxygen concentrations on the yields and kinetics of the transients, and this allows correlation to be made between the species observed immediately after excitation and the hydroxylated derivatives formed as permanent products. A mechanism is proposed which accounts for the observations in aqueous solution.