EFFECTS OF CYCLODEXTRIN COMPLEXATION ON ONE-ELECTRON REDUCTION AND ELECTRON-TRANSFER OF AROMATIC SULFONATES

Pulse radiolysis of argon-saturated aqueous solutions of sodium biphenyl-4-sulfonate (BPS-Na+) and sodium pyrene-1-sulfonate (PyS-Na+) results in the one-electron reduction of the aromatic moieties of the sulfonates by the hydrated electron to give the radical anions, BPS.2- and PyS.2-, The effects of cyclodextrin (CD) complexation of the sulfonates on the reaction rates of the one-electron reduction have been investigated. The rate constants for the one-electron reduction of BPS- and PyS- are significantly reduced by beta- and gamma-CDs, respectively, through complexation, but are hardly influenced by the other CDs including alpha-CD. The selective reduction of a mixed sulfonate system has been achieved by using beta- and gamma-CDs. The electron transfer from BPS.2- to PyS- is also retarded effectively by the complexation of PyS- with gamma-CD. The change in the transient absorption spectrum after the pulse irradiation of the PyS-Na+ solutions containing gamma-CD has suggested that the reduced 2:2 complex is unstable and dissociates into the 1:1 complexes.