Pulse radiolysis studies of functionally substituted imidazolium-based ionic liquids  

作　　者：FU HaiYing XING ZhaoGuo CAO XiYan WU GuoZhong 

机构地区：[1]Shanghai Institute of Applied Physics,Chinese Academy of Sciences,Shanghai 201800,China [2]Hunan University of Science and Technology,Changsha 411201,China

出　　处：《Chinese Science Bulletin》2012年第21期2752-2758,共7页

基　　金：supported by the National Natural Science Foundation of China(20973192,11079007)

摘　　要：The reactions of imidazolium-based ionic liquids having different substituent groups on the ring with hydrated electrons (eaq-),hydroxyl radicals (·OH),and sulfate anion radicals (SO4·-) were investigated using nanosecond pulse radiolysis techniques.The spectra of these ionic liquids on reaction with eaq-all exhibited a similar peak at about 320 nm,and a typical peak for eaq-in aqueous ionic liquid solutions.The reaction rate constants for 1,3-disubstituted imidazolium-based ionic liquid hexafluorophosphates (BMIPF 6) with eaq-were deduced to be 10 10 L mol-1s-1,however the values were lower for trisubstituted ionic liquids.For example,the rate constant for 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (BMMIBF 4) was 5.5×10 9 L mol-1s-1.Imidazolium-based ionic liquids reacted with hydroxyl radicals via adducts to produce a mixture of isomeric OH adducts,and the pk a value of the OH adducts was deduced to be 8.4±0.4 for 1-butyl-3-methylimdazolium tetrafluoroborate (BMIBF 4).Moreover,imidazolium cations were also oxidized by SO4·-to produce bivalent cation radicals,which exhibit a peak at 320 nm,and these rate constants are of the same order of magnitude,i.e.,10 9 L mol-1s-1,except that for 1-(2-hydroxyethyl)-3-methylimdazolium tetrafluoroborate with SO4·-(k=2.8×10 8 L mol-1 s-1).Theoretical calculations were carried out to estimate the structures of the products of reduction by eaq- and the results were related to the experimental data.The reactions of imidazolium-based ionic liquids having different substituent groups on the ring with hydrated electrons （eaq-）,hydroxyl radicals （·OH）,and sulfate anion radicals （SO4·-） were investigated using nanosecond pulse radiolysis techniques.The spectra of these ionic liquids on reaction with eaq-all exhibited a similar peak at about 320 nm,and a typical peak for eaq-in aqueous ionic liquid solutions.The reaction rate constants for 1,3-disubstituted imidazolium-based ionic liquid hexafluorophosphates （BMIPF 6） with eaq-were deduced to be 10 10 L mol-1s-1,however the values were lower for trisubstituted ionic liquids.For example,the rate constant for 1-butyl-2,3-dimethylimidazolium tetrafluoroborate （BMMIBF 4） was 5.5×10 9 L mol-1s-1.Imidazolium-based ionic liquids reacted with hydroxyl radicals via adducts to produce a mixture of isomeric OH adducts,and the pk a value of the OH adducts was deduced to be 8.4±0.4 for 1-butyl-3-methylimdazolium tetrafluoroborate （BMIBF 4）.Moreover,imidazolium cations were also oxidized by SO4·-to produce bivalent cation radicals,which exhibit a peak at 320 nm,and these rate constants are of the same order of magnitude,i.e.,10 9 L mol-1s-1,except that for 1-（2-hydroxyethyl）-3-methylimdazolium tetrafluoroborate with SO4·-（k=2.8×10 8 L mol-1 s-1）.Theoretical calculations were carried out to estimate the structures of the products of reduction by eaq- and the results were related to the experimental data.

关 键 词：脉冲辐解技术 离子液体 咪唑基 取代基 反应速率常数 阳离子自由基 羟基自由基 阴离子自由基 

分 类 号：O626.23[理学—有机化学]