TRANSIENT RADICALS FORMED BY ELECTRON-TRANSFER BETWEEN INORGANIC-IONSAND EXCITED AROMATIC-MOLECULES IN POLAR-SOLVENTS

Fluorescence quenching of aromatic molecules by inorganic anions has b een the subject of many investigations, yet the nature of the quenchin g mechanism is not fully understood. The fluorescence-quenching rate c onstants correlate with electrochemical data, but the radicals expecte d to form upon transfer of an electron to the excited aromatic molecul es have escaped observation. We report the first observation of radica l-ion species formed by electron-transfer quenching with inorganic ani ons in acetonitrile. A decisive step leading to formation of separated radical ions is the trapping of the primary charge-transfer complex b y a second inorganic ion.