A Vanadium-based Chemical Oscillator

Abstract

Nature abounds with examples of aperiodic functions such as hormonal, daily, and seasonal cycles and cardiac rhythms, but establishing a chemical basis of these oscillations has been difficult. Efforts to provide chemical models for the study of oscillating phenomena have focused on halogen-, sulfur-, and manganese-based systems. We show here that a vanadium-based chemical system exhibits oscillatory behavior similar to circadian and other aperiodic rhythms.

A Vanadium‐Based Chemical Oscillator: Identification of Chemical Species Responsible for the Redox Reaction and Construction of a Simplified Model

“…[8][9][10][11][12][13][14] CH 2 Cl 2 Ǟ hν · Cl + · CH 2 Cl (1) · Cl + CH 2 Cl 2 Ǟ HCl + · CHCl 2 (2) In addition to the above products, phosgene, CCl 4 , and CO 2 have also been observed. [7] This is consistent with two observations: the oscillation reaction did not occur in the dark, and illumination with UV light significantly shortened the induction period. [15] Photoinduced homolytic cleavage of C-Cl bonds in dichloromethane produces Cl · and · CH 2 Cl radicals, which then initiate the radical chain reaction as shown above.…”

“…[8] Based on the above conclusion, a simplified, theoretical model was constructed to simulate the oscillation behavior. This assumption is supported by an intense band at 447 nm in the absorption spectrum of the V V complex, [7] and data that show an enhancement in the reduction of V V when irradiated with visible light. A probable reductant could not be identified.…”

“…Oxidohalogenates such as BrO 3 are often used as an oxidant. [7] The observed color change between pale green and dark orange has been attributed to the V IV /V V redox couple. Oscillation phenomena in general depend on a complicated balance of materials.…”

“…Manganese, cerium, or iron compounds have been used as the metal catalyst, and sulfuric acid is the most commonly employed acid. [7] Other features of this oscillating system were as follows. However, we have recently discovered that oscillating behavior can be observed in simple solutions of certain vanadium compounds, such as [V IV OCl 2 (bpy)] or [V III Cl 3 (CH 3 CN)(bpy)] (bpy: 2,2Ј-bipyridine), in dichloromethane.…”

Physiological roles of peroxido-vanadium complexes: Leitmotif as their signal transduction pathway

“…If the electron transfer takes place in the vanadium complex, the solution color changes dramatically. For both intra-and intermolecular electron transfer reactions, an oscillation reaction has been observed [3,4,5]. The electron transfer reaction is ubiquitous in our body, and if oxygen is present in the vicinity of the site of the electron transfer reaction, it is quite reasonable…”