Laser photolysis studies of quaternary ammonium ionic liquids aqueous solution

The reactions between quaternary ammonium ionic liquids (Me₃NC₂H₄OH]⁺Zn₂Cl₅]⁻, abbrev. Ch-Zn₂Cl₅) and one-electron oxidant (SO₄^•−), have been studied by nano-second laser photolysis techniques. The mechanism of monophotonic ionization by 266 nm laser excitation was suggested and the quantum yield was estimated to be 0.04. The second-order decay rate constant of SO₄^•− oxidation reactions at 460 nm, 1.3 × 10⁹ M⁻¹ s⁻¹, was almost equal to the product rate constant of 1.5 × 10⁹ M⁻¹ s⁻¹ at 320 nm in Ch-Zn₂Cl₅ aqueous solution showing that the decay and the product were synchronic. Comparison of Ch-Zn₂Cl₅ with chloride choline and ZnCl₂ showed that the anion Zn₂Cl₅ ⁻ played an important role in photoionization while choline cation had little function on its photolysis and radiolysis. The present study would be helpful for understanding the application of ionic liquids in the field of electrochemical deposition.