Structures of 4-Substituted Thioanisole Radical Cations Studied by Time-resolved Resonance Raman Spectroscopy during Pulse Radiolysis and Theoretical Calculations
Structures of 4-Substituted Thioanisole Radical Cations Studied by Time-resolved Resonance Raman Spectroscopy during Pulse Radiolysis and Theoretical Calculations
复制标题
脉冲放射分解过程中时间分辨共振拉曼光谱研究4-取代苯硫基自由基阳离子的结构及理论计算
DOI：
10.1039/c6ra21460f
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
and T. Majima
中科院分区：
文献类型：
--
作者：
S. Tojo;M. Fujitsuka;and T. Majima
为了解二聚反应活性，采用脉冲辐解的纳秒时间分辨拉曼（ns-TR 3）光谱和密度泛函理论（DFT）计算研究了4-取代苯甲醚自由基阳离子（ArSCH 3 stec+）在水溶液中的结构.观察到苯环的CC伸缩模式的下移和氧化后的C-S伸缩模式的上移与芳族硫化物，如4-羟甲基苯甲醚（MTPM），表明形成半醌型结构。对于4-甲氧基茴香硫醚自由基阳离子（MTA stec+），弱CPh-O伸缩另外观察到。基于密度泛函理论计算，MTPM stec+等分子均为含S原子和苯环的半醌型结构，其正电荷和自旋分别位于S原子和C4-位.另一方面，包括S和O原子和苯环的醌式结构被指示为MTA stec+。DFT计算结果与ArSCH_3stec+的TR_3谱符合得很好。从S非键电子与芳香体系π电子的共轭角度讨论了ArSCH_3stec ~+的二聚反应活性。
To understand dimerization-reactivity, structures of 4-substituted thioanisole radical cations (ArSCH3˙+) in aqueous solution were studied by the nanosecond time-resolved resonance Raman (ns-TR3) spectroscopy during pulse radiolysis and density functional theory (DFT) calculations. The downshift of the CC stretching mode of the benzene ring and the upshift of the C–S stretching mode upon oxidation were observed with aromatic sulfides such as 4-hydroxymethylthioanisole (MTPM), suggesting formation of a semi-quinoidal structure. For the 4-methoxythioanisole radical cation (MTA˙+), weak CPh–O stretching was observed additionally. Based on the DFT calculations, semi-quinoidal structures including an S atom and benzene ring were indicated for MTPM˙+ and so on, in which the positive charge and spin are localized on the S-atom and C4-position, respectively. On the other hand, the quinoidal structure including the S and O atoms and benzene ring was indicated for MTA˙+. The results of DFT calculation agreed well with TR3 spectra of ArSCH3˙+. The reactivities of ArSCH3˙+ toward dimerization were discussed in terms of the conjugation between S non-bonding electrons and π-electrons of the aromatic system.