[Me_3NC_2H_4OH]Zn_2Cl_5水溶液的激光光解研究

Studies of [Me_3NC_2H_4OH]Zn_2Cl_5 Aqueous Solution by Laser Photolysis

利用时间分辨激光光解技术研究了季铵盐型离子液体[Me3NC2H4OH]Zn2Cl5(简写R-Zn2Cl5)的光解行为,研究发现离子液体能被266nm激光单光子电离,生成阳离子自由基、[Zn2Cl5]?中性自由基和水合电子,观察到胆碱激发三线态的存在,并测定了离子液体光电离的量子产额为0.04.利用266nm激光对离子液体、胆碱、氯化锌、氯化钠的光解行为比较,发现胆碱阳离子的贡献很小,[Zn2Cl5]-阴离子起主要作用.采用氧化性自由基SO?4-引发离子自由基,揭示其光电离机理,测定离子液体的动力学反应速率常数,SO?4-460nm的衰减速率常数为1.3×109L?mol-1?s-1,320nm离子自由基瞬态产物的生成速率常数为1.5×109L?mol-1?s-1,两者很接近,说明SO?4-自由基的衰减与瞬态自由基的生成是同步的.

The absorption spectra of [Me3NC2H4OH]Zn2Cl5 （R-Zn2Cl5） in aqueous solutions were studied by time-resolved laser photolysis, and the mechanism of monophotonic ionization was suggested. The oxidizing radical SO4^·- was used to produce radical cation. Comparison of R-Zn2Cl5 with NaCl, ZnCl2 and choline showed that [Zn2Cl5]^- played an important role in photoionization while [Me3NC2H4OH]^·＋ cation had little function on its photolysis. Rate constant for oxidation reactions was determined in R-Zn2Cl5 ionic liquid. The second-order decay rate constant of SO4^·- oxidation reactions at 460 nm, 1.3 × 10^9 L·mol^-1·s^-1, was almost equal to the product rate constant of 1.5 × 10^9 L·mol^-1·s^-1 at 320 nm in R-Zn2Cl5 aqueous solution, showing that the decay and the product were synchronic.