Nonlinear dynamical behavior in the photodecomposition of N-bromo-1,4-benzoquinone-4-imine

Photodecomposition of N-bromo-1,4-benzoquinone-4-imine in water with and without the presence of oxidants was investigated, exhibiting nonlinear kinetic features such as autocatalytic excursion. An acidic environment was found to be essential for the observed photodecomposition. Mechanistic studies through NMR and mass spectrometry show the conversion of N-bromo-1,4-benzoquinone-4-imine into 1,4-benzoquinone. When bromate was introduced to the studied system, transient spontaneous oscillations were uncovered, forming a new photocontrolled chemical oscillator. The system's sensitivity to the intensity of the illumination is great as decreases halt the oscillations from occurring. Phase diagrams show that as the concentration of N-bromo-1,4-benzoquinone-4-imine is increased, broader concentration ranges of both bromate and sulfuric acid allow the system to exhibit spontaneous oscillations. Electrospray-TOF mass spectroscopy and (13)C NMR spectra suggest that 3,4,4-tribromo-2-hydroxycyclohexa-2,5-dienone is a major product in the bromate system.