Electrochemical behavior of a Cypridina luciferin analogue in acetonitrilesolutions in the presence of proton acceptors

The electrochemical redox behavior of the Cypridina luciferin analogue, 6-( 4-methoxyphenyl)-2-methylimidazo[1, 2-a]pyrazin-3(7H)-one (MCLA) has been e xamined in acetonitrile solutions containing 2,6-lutidine or water using cy clic and hydrodynamic voltammetry and double potential-step chronoamperomet ry. The conjugate base of MCLA (MCLA(-)) is oxidized in two one-electron st eps to the radical species (MCLA(.)) and further to the carbocation species (MCLA(+)). The radical-radical coupling of MCLA(.) yields the correspondin g dimer ((MCLA)(2)), which is in equilibrium with MCLA(.). MCLA(+) undergoe s the addition of a water molecule to yield a hydroxylated form (MCLA-OH) o f luciferinol type. The whole mechanism of the electrochemical redox reacti ons of MCLA(-) coupled with these chemical reactions has been found to be e ssentially the same as that proposed for the chemical redox reactions of Cy pridina luciferin and its analogues, and in addition the kinetic data. conc erning the dimerization of MCLA(.), the dissociation of (MCLA)(2) and the h ydroxylation of MCLA(+) have been estimated together with the diffusion coe fficient of MCLA(-). (C) 1999 Elsevier Science S.A. All rights reserved.