Magnetic field effects on chemical reactions of biradical radical ion pairs in homogeneous fluid solvents
Magnetic field effects on chemical reactions of biradical radical ion pairs in homogeneous fluid solvents
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DOI：
10.1021/jp0007437
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发表时间：
2000-06-01
影响因子：
2.9
通讯作者：
Hayashi, H
中科院分区：
文献类型：
--
作者：
Mori, Y;Sakaguchi, Y;Hayashi, H
研究了磁场对10-甲基吩噻嗪（（3）MPTZ*）（S = 1）与2，2，6，6-四甲基哌啶-1-氧（克里思）连接的电子受体（An-R-）三重态电子转移（ET）反应的双自由基离子对（BRIPs，S = 3/2和1/2）反应的影响.（S1/2）在各种溶剂中通过纳秒激光光解技术。在异丙醇中，随着磁场（B）从0 T增加到2 T，自由离子的产率显著增加，但从2 T增加到10 T，自由离子的产率略有下降。MFE的幅度远大于在3 MPTZ * 与受体而没有克里思（S = 0）的ET反应中观察到的那些。为了解释与An-R-反应中观察到的MFE，（.）我们考虑了以下两个因素。(i)在An-R-对（3）MPTZ ~* 的猝灭作用中。不仅发生ET反应，而且发生三重态-二重态（T-D）淬灭。T-D猝灭效率随B的增加而降低，导致BRIPs（[MPTZ（.+）一个（.-）- R-.]）。然而，这个因素被发现只有一个小的贡献，所观察到的MFE的自由离子产率。(ii)ET反应生成（4.2）[MPTZ（.+）一个（.-）- R-.]在四重态（Q）和二重态（D）中，其通过从D态的自旋选择性反向ET或分离到自由离子而衰减。在B = 0 T时，Q和D态之间的自旋转换是有效的。随着B从0增加到2 T，自由离子产率的增加可以归因于由于（3）（An（.-）-N）的偶极-偶极相互作用而导致的从Q（+/-3/2）态到Q（+/-1/2）和D+/-1/2态的自旋弛豫。R-.）。随着B从2 T增加到10 T，自由离子产额的轻微降低可以归因于由各向异性塞曼相互作用引起的弛豫的加速和/或由MPTZ（.+）之间各向同性g因子的差异引起的Q（+/-1/2）-D+/-1/2转换的增强。和（.-）- R...研究了溶剂和添加剂对微乳液性能的影响。
Magnetic field effects (MFEs) on reactions of biradical radical ion pairs (BRIPs, S = 3/2 and 1/2) were investigated for the electron transfer (ET) reactions of the triplet State of 10-methylphenothiazine ((3)MPTZ*) (S = 1) and electron accepters linked with 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) (An-R-.) (S 1/2) in various solvents by means of a nanosecond laser photolysis technique. In 2-propanol, the yield of free ions dramatically increased with increasing magnetic field (B) from 0 to 2 T, but slightly decreased from 2 to 10 T. The magnitude of the MFEs was much larger than those observed in ET reactions of 3MPTZ* with acceptors without TEMPO (S = 0). To interpret the MFEs observed in the reactions with An-R-,(.) we considered the following two factors. (i) In the quenching of (3)MPTZ* by An-R-. not only the ET reaction but also triplet-doublet (T-D) quenching takes place. The T-D quenching efficiency decreases with increasing B, resulting in a higher yield of BRIPs ([MPTZ(.+) An(.-)-R-.]). However, this factor was found to have only a small contribution to the observed MFEs on the free ion yield. (ii) The ET reactions generate (4.2)[MPTZ(.+) An(.-)-R-.] in quartet (Q) and doublet (D) states, which decay through either the spin-selective back ET from the D states or the separation to free ions. At B = 0 T, the spin conversion between the Q and D states is efficient. The increase in the free ion yield with increasing B from 0 to 2 T can be attributed to the spin relaxation from the Q(+/-3/2) states to the Q(+/-1/2) and D+/-1/2 states due to the dipole-dipole interaction of (3)(An(.-)-R-.). The slight decrease in the free ion yield with increasing B from 2 to 10 T can be attributed to acceleration of the relaxation induced by the anisotropic Zeeman interaction and/or enhancement of the Q(+/-1/2)-D+/-1/2 conversion induced by the difference in the isotropic g-factor between MPTZ(.+) and An(.-)-R-.. Effects of solvents and additives on the present MFEs were also studied.