ON THE MECHANISM OF A MODEL QUERCETINASE REACTION USING A COBALT SCHIFF-BASE COMPLEX

Cyclic voltammetry of a substrate anion-catalyst binary complex interm ediate [Co(III)(salen)L1] [substrate = various flavonols (HL1); H-2sal en = N,N'-bis(salicylidene)ethane-1,2-diamine] in a model quercetinase reaction using [Co(II)(salen)] as catalyst has revealed that the inte rmediate partly undergoes ionic dissociation in dimethylformamide (dmf ) to give L1 and [Co(III)(salen) (dmf)2]+. Dioxygen is then incorporat ed into the flavonolate anion in a non-radical manner, which is promot ed by the counter cobalt cation complex, finally to give (Co(III)(sale n) L2(dmf)] (HL2 = a depside product) which then forms L2 and [Co(III) (salen)(dmf)2]+. The reaction rate was affected by the nature of the c ation employed: [Co(III)(salen) (dmf)2]+ is more effective than K+.