Highly efficient electrochemiluminescence of quinoline and isoquinoline in aqueous solution

This paper reports for the first time the strong cathodic electrochemiluminescence (ECL) behavior of quinoline, isoquinoline and their derivatives in aqueous solution with K2S2O8 as coreactant. The effects of K2S2O8 concentration, pH and scan rate on the ECL intensity have been studied in detail. Calculations of the HOMO-LUMO energy gap for the ECL reaction indicated that isoquinoline is more likely to produce an excited state radical ion than quinoline. The effects of different functional groups on the ECL of isoquinoline were then compared and a possible ECL reaction mechanism was discussed. This work provides a simple and sensitive ECL method for the detection of quinoline and isoquinoline, which are important drug intermediates.