Influence of Visible Light and Malonic Acid Derivatives on the Autocatalytic Oxidation of Ru(II) by Bromate Ions

The Tris(2,2'-Bipyridyl)Ruthenium-Catalysed Belousov–Zhabotinsky Reaction

The Belousov – Zhabotinsky (BZ) reaction is the prototypical oscillating chemical reaction. The tris(2,2'-bipyridine)ruthenium-catalysed BZ reaction (often simply referred to as the ruthenium-catalysed BZ reaction) displays photosensitivity and has been widely exploited for examination of the effects of illumination on nonlinear reaction kinetics. In this review, we investigate the behaviour of the ruthenium-catalysed BZ reaction. The mechanism of the reaction is analysed and we examine how light sensitivity is incorporated into kinetic models of the reaction. The temporal dynamics of the photosensitive reaction is presented and, finally, we discuss the extraordinary wealth of behaviour that has been observed in the spatially-distributed system when perturbed by visible light.

Mixed mode and sequential oscillations in the cerium-bromate-4-aminophenol photoreaction

Cerium was introduced to the bromate-aminophenol photochemical oscillator to implement coupled autocatalytic feedbacks. Mixed mode and sequential oscillations emerged in the studied system, making it one of the few chemical oscillators known to support consecutive bifurcations in a batch system. The complex reaction behavior showed a strong dependence on the intensity of illumination supplied to the system. Removal of illumination during an oscillatory window affected both the frequency and amplitude of the oscillation but did not fully extinguish them, indicating that the cerium-bromate-4-aminophenol oscillator was photosensitive rather than photo-controlled. A moderate light intensity allowed for a slow evolution of the system, which proved to be critical for the emergence of transient complex oscillations. Variation of individual reaction parameters was carried out, which indicated that the development of complex oscillations occur in a narrow region and a phase diagram in the 4-aminophenol and sulfuric acid plane demonstrated this. Simulations provide strong support that transient complex oscillations observed experimentally arise from the coupling of two autocatalytic cycles.

Complex dynamical behavior in the highly photosensitive cerium-bromate-1,4-benzoquinone reaction

Experimental and numerical investigations are carried out on the nonlinear dynamics of the cerium-bromate-1,4-benzoquinone reaction in which a unique kinetic feature is that the reduction of Ce(IV) is through bromide ions rather than by organic substrates. Nonlinear phenomena including both simple and sequential oscillations have been observed, and the system could oscillate for longer than a week. Significantly, fluorescent ceiling light with an intensity of less than 20 μW/cm(2) exhibited strong influence on the frequency, lifetime, and complexity of the spontaneous oscillations. The transient oscillations lasted for a longer period of time at a low light intensity, were quenched by a moderate illumination, and then became long-lived again at a higher light intensity. Characterizations with (1)H NMR and GC/MS spectroscopy and ion selective electrode suggest that 2-bromo-1,4-benzoquinone is an important unstable intermediate product that undergoes photoaccelerated decomposition to produce hydroxy-1,4-benzoquinone and bromide ions. Simulations successfully reproduced the occurrence of oscillatory behavior in the studied system.