Photoinduction and photoinhibition of chemical oscillations in the tris(2,2′-bipyridine) ruthenium (II)-catalyzed minimal bromate oscillator

Reaction Mechanism for Light Sensitivity of the Ru(bpy)32+-Catalyzed Belousov−Zhabotinsky Reaction

“…9,15,17 Hanazaki at al. 16,[18][19][20][21] proposed a dual effect of light on the BZ reaction: low-intensity illumination inducing oscillations, due to the generation of HBrO 2 from BrO 3 -, and high-intensity illumination suppressing oscillations, due to the generation of Brfrom BrO 3 -. For our experimental conditions, which correspond to low-intensity illumination, the excited ruthenium(II) reduces bromate in the initiation reaction 21 followed by the autocatalytic cycle:…”

“…7 Kuhnert 9 and, later, Jinguji et al 15 therefore proposed that Ru(bpy) 3 2+ * serves to reduce the reactant BrO 3 -to Br -, which is the primary autocatalysis inhibitor in the BZ reaction. An indirect path for the photochemical reduction of bromate to bromide in the presence of oxygen has also been proposed by Reddy et al 17 In a series of papers, Hanazaki and co-workers 16,[18][19][20][21] have examined the photochemical mechanism for the inorganic subset of the ruthenium-catalyzed BZ reaction, namely the illuminated Ru(bpy) 3 2+ -bromate reaction in sulfuric acid. They proposed a scheme involving the photochemical production of the autocatalyst HBrO 2 and the inhibitor Brto account for the experimentally observed inhibition as well as inducement of oscillatory behavior by light.…”

“…They proposed a scheme involving the photochemical production of the autocatalyst HBrO 2 and the inhibitor Brto account for the experimentally observed inhibition as well as inducement of oscillatory behavior by light. 20,21 Much less is known about the photochemical reactions of the organic subset of the ruthenium-catalyzed BZ reaction. The importance of the organic subset in the light sensitivity has been recently suggested, 17,21,22 and the role of bromomalonic acid (BrMA) as a bromide source has been pointed out by Yamaguchi and co-workers.…”

Photoinduced Bifurcation and Multistability in the Oscillatory Briggs−Rauscher Reaction

“…Photoinduced bifurcations such as the photoinduction and -inhibition of chemical oscillations in well-stirred homogeneous solutions have been discovered for several systems. [1][2][3][4][5][6][7][8][9][10] The image formation and its modulation by light irradiation in unstirred solutions have also been reported. [11][12][13][14] The use of light is advantageous in the investigation of nonlinear chemical systems not only for its feasibility in changing irradiation power and wavelength, but also for its possibility in elucidating the reaction mechanism with a wider perspective.…”

“…These bifurcations can be understood with the model discussed above.As can be seen fromFigure 6, the bifurcations taking place across γ I and γ O-are extentions of the dark bifurcations modified by the light irradiation. The positive slopes for both curves in the ([I -] 0 , P)-plane indicate that the critical values of [I -] 0 for these bifurcations tend to increase with P. Whether I -is produced or consumed by the light irradiation is predictable from the slope of a bifurcation curve, provided that [I -] th is held constant along the bifurcation curve 7,9. The steep positive slope of γ I would suggest slow consumption of I -in SSI by light irradiation, which is compensated by the increase of external supply of I -to keep [I -] > [I -] th .…”