The light-perturbed Ru-catalyzed Belousov-Zhabotinsky reaction: Evidence for photochemically produced bromous acid and bromide ions by phase responseanalysis

Phase response analysis of light-perturbed closed and aging Ru-catalyzed Be lousov-Zhabotinsky (BZ) reactions with malonic, methyl-, ethyl-, butyl-, an d phenylmalonic acids as organic substrates suggests two major responses of the light-perturbed Ru-catalyzed BZ system. One is the photoproduction of bromous acid (HBrO2) in the beginning of the reaction when little bromoorga nic species are present, while another response is the photoproduction of b romide ions in the presence of bromomalonic acid or bromomalonic acid deriv atives. From this analysis the light-induced production of bromide ions dir ectly from bromate can be excluded. The experimentally observed phase respo nse curves agree well with calculations performed with the Oregonator model . An oxidative quenching mechanism for the photoproduction of bromide is su ggested. Interestingly, during illumination of the Ru(II)/MA subsystem, i.e ., in the absence of BrMA and bromate, the oxidative quenching does also oc cur.