Diffusion and Solvation of Radical Ions in an Ionic Liquid Studied by the MFE Probe
Diffusion and Solvation of Radical Ions in an Ionic Liquid Studied by the MFE Probe
复制标题
用 MFE 探针研究离子液体中自由基离子的扩散和溶解
DOI：
10.1021/jp5069544
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Masanobu Wakasa,
中科院分区：
文献类型：
--
作者：
Tomoaki Yago;Yuya Ishii;Masanobu Wakasa,
采用纳秒激光闪光光解技术研究了磁场效应（MFE）对二苯甲酮（BP）与1,4-二氮杂双环[2.2.2]辛烷在N,N,N-三甲基-N-丙基双（三氟甲磺酰基）酰胺离子液体（IL）中光致电子转移反应的影响。二苯甲酮自由基阴离子（BP·–）的逃逸产率随着0 T <B≤ 0.1 T的磁场强度（B）的增加而增加，并在0.1 T <B≤ 1.7 T时几乎饱和。观察到的MFE由超精细耦合机制（HFCM）和弛豫机制（RM）解释。大的 MFE 表明纳米级笼效应对 TMPA TFSA 中光诱导电子转移反应产生的自由基离子对 (RIP) 的扩散产生影响。 RIP 的笼寿命估计为 170 ns，比之前报道的相同 IL 中的中性自由基对 (<20 ns) 长得多。除了 HFCM 和 RM 引起的大 MFE 之外，我们还观察到由电平交叉机制 (LCM) 引起的 MFE。这些结果表明，与中性自由基相比，自由基离子在离子液体中被严格溶剂化，并且在自由基离子周围产生纳米级电荷排序结构。
Magnetic field effects (MFEs) on photoinduced electron transfer reaction between benzophenone (BP) and 1,4-diazabicyclo [2.2.2] octane in an ionic liquid (IL) ofN,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl) amide were studied by a nanosecond laser flash photolysis technique. The escape yield of the benzophenone radical anion (BP•–) was increased with increasing magnetic field strength (B) of 0 T <B≤ 0.1 T and almost saturated at 0.1 T <B≤ 1.7 T. The observed MFEs were explained by the hyperfine coupling mechanism (HFCM) and the relaxation mechanism (RM). The large MFEs indicate the nanometer-scaled cage effects on the diffusion of the radical ion pairs (RIP) generated by the photoinduced electron transfer reaction in TMPA TFSA. The cage lifetime for the RIP was estimated to be 170 ns, which is much longer than that previously reported for the neutral radical pairs (<20 ns) in the same IL. In addition to the large MFEs due to the HFCM and the RM, we also observed the MFE caused by the level crossing mechanism (LCM). These results suggest that compared with the neutral radicals, the radical ions are rigidly solvated in the IL and the nanometer-scaled charge-ordering structures are created around the radical ions.