Department of Chemistry, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan.
Phys Chem Chem Phys. 2012 Mar 14;14(10):3490-7. doi: 10.1039/c2cp23747d. Epub 2012 Feb 3.
Magnetic field effects (MFEs) on the photoinduced hydrogen abstraction reaction of benzophenone with phenol were investigated in ionic liquids (ILs) with a short alkyl chain (N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)amide (TMPA TFSA)) and long alkyl chains ((N,N,N-trimethyl-N-octylammonium bis(trifluoromethanesulfonyl)amide (TMOA TFSA) and N-decyl-N,N,N-trimethylammonium bis(trifluoromethanesulfonyl)amide (DTMA TFSA)) by a nanosecond laser flash photolysis technique. In each ionic liquid, escaped radical yield of a benzophenone ketyl radical rapidly increased with increasing magnetic field strength (B) of 0 T < B≤ 0.01 T. At 0.01 T < B≤ 0.4 T, the escaped radical yield almost saturated in TMPA TFSA or gradually increased in TMOA TFSA and DTMA TFSA. At much higher fields of 0.4 T < B≤ 30 T, the yield gradually decreased, resulting in 10-15% decrease at 30 T. The observed MFEs can be explained by the hyperfine coupling and Δg mechanisms together with the relaxation mechanism. On the time profiles of the transient absorption observed for the benzophenone ketyl radical, MFEs were generated in the time range of 0 < t < 0.6 μs. The cage lifetimes of TMOA TFSA and DTMA TFSA were estimated to be at least 120 ns.
磁场效应（MFEs）对离子液体（ILs）中苯甲酮与苯酚的光诱导氢提取反应的影响进行了研究，离子液体具有短链烷基（N，N，N-三甲基-N-丙基铵双（三氟甲烷磺酰基）酰胺（TMPA TFSA））和长链烷基（（N，N，N-三甲基-N-辛基铵双（三氟甲烷磺酰基）酰胺（TMOA TFSA）和 N-癸基-N，N，N-三甲基铵双（三氟甲烷磺酰基）酰胺（DTMA TFSA）），通过纳秒激光闪光光解技术。在每种离子液体中，苯甲酮酮基自由基的逃逸自由基产率随磁场强度（B）的增加而迅速增加，0 T < B≤ 0.01 T。在 0.01 T < B≤ 0.4 T 时，在 TMPA TFSA 中，逃逸自由基产率几乎饱和，而在 TMOA TFSA 和 DTMA TFSA 中逐渐增加。在更高的磁场强度 0.4 T < B≤ 30 T 下，产率逐渐降低，在 30 T 时降低了 10-15%。观察到的磁场效应可以通过超精细耦合和Δg 机制以及弛豫机制来解释。在观察到的苯甲酮酮基自由基的瞬态吸收时间谱上，在 0 < t < 0.6 μs 的时间范围内产生了磁场效应。TMOA TFSA 和 DTMA TFSA 的笼寿命估计至少为 120 ns。
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