The phosphate ester I,l'-binaphthyl-2.2'-diyl-phosphate shows an intense fluorescence of the binaphthyl moiety. In the complex l , I'-binaphthyl-2,2'-diyl-phosphato-pent~ne-cobalt(III) this emission is quenched by excited state electron transfer to Co(m). As a consequence the phosphate ester undergoes an oxidative cleavage whde Co(III) is reduced to Co(lI) with 4=0.023+0.002 at 1,,=313 nm.