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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Reaction Pathways of the Electron Transfer from Photoexcited 10-Methylphenothiazines to Electron Acceptors in Polar Solvents. Effects of Magnetic Fields and Heavy Atoms on Efficiency of Free Ion Formation
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Reaction Pathways of the Electron Transfer from Photoexcited 10-Methylphenothiazines to Electron Acceptors in Polar Solvents. Effects of Magnetic Fields and Heavy Atoms on Efficiency of Free Ion Formation

机译：电子从光激发的10-甲基吩噻嗪转移到极性溶剂中的电子受体的反应途径。磁场和重原子对自由离子形成效率的影响

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The lowest triplet excited states of (2-substituted), IO-methylphenothiazine were found to be quenched by various electron acceptors in polar solvents such as 2~propanol and acetonitrile through electron transfer (ET). The transient absorption and time-resolved EPR spectra indicated that the radical cation of the phenothiazine and radical anions of the acceptors were fonned as the ET products in moderate to high yields. These free radical ions were fonned via two types of intermediates, {i) a triplet contact radical ion pair (3CRIP) or a triplet exciplex (3Ex*)and (ii) a triplet solvent-separated radical ion pair (3SSRIP). In the quenching by the Br-substituted acceptors, a large fraction of 3CRIP (or 3Ex*) was deactivated to the singlet ground states due to the breakdown of the spin-forbiddance by strong spin-;-orbit coupling. On the other hand, 3CRIP (or 3Ex*) containing no heavy atom was mainly transfonned into 3SSRIP by solvation. 3SSRIP decayed through either the separation to free ions or the 1:riplet-singlet conversion followed by the spin-allowed backward ET to the ground states. The backward ET rates of ISSRIPs were estimated to be 2: 109 S-I, even when the reaction fell into the deeply inverted region. In 2-propanol, the free ion yields were affected by magnetic fields. The magnitudes of magnetically induced changes strongly depended on the polarity and viscosity of solvents, suggesting that the separation rate ofSSRIP should be a crucial factor detennining the field dependence of the .free ion yields.
机译：发现（2-取代的）IO-甲基吩噻嗪的最低三线态激发态通过电子转移（ET）在极性溶剂如2-丙醇和乙腈中被各种电子受体猝灭。瞬态吸收和时间分辨的EPR光谱表明，吩噻嗪的自由基阳离子和受体的自由基阴离子以中等至高产率形成为ET产物。这些自由基离子通过两种类型的中间体形成：（i）三重态接触自由基离子对（3CRIP）或三重态激基复合物（3Ex *）和（ii）三重溶剂分离的自由基离子对（3SSRIP）。在通过Br取代的受体进行淬灭中，由于强自旋-轨道耦合导致自旋禁忌的分解，很大一部分3CRIP（或3Ex *）被失活为单线基态。另一方面，不包含重原子的3CRIP（或3Ex *）主要通过溶剂化而转变为3SSRIP。 3SSRIP通过分离成游离离子或通过1：riplet-Singlet转换衰减，然后自旋允许向后ET下降到基态而衰减。 ISSRIP的向后ET率估计为2：109 S-1，即使反应落入深度倒置的区域也是如此。在2-丙醇中，自由离子产率受磁场影响。磁感应变化的幅度在很大程度上取决于溶剂的极性和粘度，这表明SSRIP的分离速率应该是决定自由离子产率的场依赖性的关键因素。

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