Switched external magnetic field CIDNP studies of coupling reaction of carbon-centered radicals with TEMPO
Switched external magnetic field CIDNP studies of coupling reaction of carbon-centered radicals with TEMPO
复制标题
碳中心自由基与 TEMPO 偶联反应的切换外磁场 CIDNP 研究
DOI：
10.1039/b401093k
复制
发表时间：
2004
影响因子：
3.3
通讯作者：
P. Tordo
中科院分区：
文献类型：
--
作者：
N. Lebedeva;D. Zubenko;E. Bagryanskaya;R. Sagdeev;G. Ananchenko;S. Marque;D. Bertin;P. Tordo
利用CIDNP方法研究了在开关外磁场（SEMF）作用下，苯中碳中心自由基与持久性硝酰基自由基克里思（2，2，6，6-四甲基哌啶基-N-氧基）的反应.在克里思存在下，通过激光脉冲光解相应的酮前体RC（O）R，利用众所周知的光化学产生碳中心自由基。对SEMF CIDNP的理论背景进行了修正，得到了相应的动力学方程组的解析解，在自由基初始浓度R较低的情况下，SEMF CIDNP动力学符合单指数衰减方程kc[Y]+1/T1，其中kc
- 烷基和硝酰基自由基之间的偶联速率常数，[Y]
- 硝酰基自由基的浓度和T1
- 瞬态自由基的电子-核弛豫时间。不同浓度的氮氧化物的SEMF CIDNP动力学分析使我们能够推导出相应的kc值，这与文献中发现的激光闪光光解实验的结果进行了比较。不同的方法之间取得了良好的协议。
CIDNP in a switched external magnetic field (SEMF) is applied to study reactions of carbon-centered radicals with the persistent nitroxyl radical TEMPO (2,2,6,6-tetramethylpiperidinyl-N-oxyl) in benzene. The carbon-centered radicals were generated by laser pulse photolysis of the corresponding ketone precursors RC(O)R with well-known photochemistry in the presence of TEMPO. Theoretical background of SEMF CIDNP was adapted to the system under study and the analytical solution of the corresponding set of kinetic equations was found. In the case of low initial concentration of radicals R the SEMF CIDNP kinetics are expected to be monoexponential with decay equal to kc[Y] + 1/T1, where kc
— coupling rate constant between alkyl and nitroxyl radicals, [Y]
— concentration of nitroxyl radicals, and T1
— electron-nuclear relaxation time of transient radicals. Analysis of SEMF CIDNP kinetics with varied concentrations of nitroxide allowed us to derive the corresponding kc values, which were compared with the results of laser flash photolysis experiments found in the literature. Good agreement between different methods is achieved.