...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Intramolecular charge transfer with the planarized 4-cyanofluorazene and its flexible counterpart 4-cyano-N-phenylpyrrole. Picosecond fluorescence decays and femtosecond excited-state absorption
【24h】

Intramolecular charge transfer with the planarized 4-cyanofluorazene and its flexible counterpart 4-cyano-N-phenylpyrrole. Picosecond fluorescence decays and femtosecond excited-state absorption

机译：用平面化的4-氰基氟腈及其柔性的对应物4-氰基-N-苯基吡咯进行分子内电荷转移。皮秒荧光衰减和飞秒激发态吸收

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The fluorescence spectrum of the rigidified 4-cyanofluorazene (FPP4C) in n-hexane consists of a dual emission from a locally excited (LE) and an intramolecular charge-transfer (ICT) state, with an ICT/LE fluorescence quantum yield ratio of Phi'(ICT)/Phi(LE) = 3.3 at 25 degrees C. With the flexible 4-cyano-N-phenylpyrrole (PP4C) in n-hexane, such an ICT reaction also takes place, with Phi'(ICT)/Phi(LE) = 1.5, indicating that for this reaction, a perpendicular twist of the pyrrole and benzonitrile moieties is not required. The ICT emission band of FPP4C and PP4C in n-hexane has vibrational structure, but a structureless band is observed in all other solvents more polar than the alkanes. The enthalpy difference Delta H of the LE -> ICT reaction in n-hexane, -11 kJ/mol for FPP4C and -7 kJ/mol for PP4C, is determined by analyzing the temperature dependence of Phi'(ICT)/Phi(LE). Using these data, the energy E(FC,ICT) of the Franck-Condon ground state populated by the ICT emission is calculated, 41 (FPP4C) and 40 kJ/mol (PP4C). These large values for E(FC,ICT) lead to the conclusion that with FPP4C and PP4C, direct ICT excitation, bypassing LE, does not take place. FPP4C has an ICT dipole moment of 15 D, similar to that of PP4C (16 D). Picosecond fluorescence decays allow the determination of the ICT lifetime, from which the radiative rate constant k(f)'(ICT) is derived, with comparable values for FPP4C and PP4C. This shows that an argument for a twisted ICT state of PP4C cannot come from k(f)'(ICT). After correction for the solvent refractive index and the energy of the emission maximum (v) over tilde (max)(ICT), it appears that k(f)'(ICT) is solvent-polarity-independent. Femtosecond transient absorption with FPP4C and PP4C in n-hexane reveals that the ICT state is already nearly fully present at 100 fs after excitation, in rapid equilibrium with LE. In MeCN, the ICT state of FPP4C and PP4C is likewise largely developed at this delay time, and the reaction is limited by dielectric solvent relaxation, which shows that the ICT reaction is ultrafast, at the experimental time limit of 50 fs. PP4C and FPP4C have a similar planar ICT structure, without an appreciable twist of the pyrrole and benzonitrile subgroups. Their crystal structure is compared with calculations for the S-0 ground state.
机译：正己烷中硬化的4-氰基氟腈（FPP4C）的荧光光谱由局部激发（LE）和分子内电荷转移（ICT）状态的双重发射组成，ICT / LE荧光量子产率比为Phi '（ICT）/ Phi（LE）= 25°C时为3.3。在正己烷中使用柔性的4-氰基-N-苯基吡咯（PP4C）时，也会发生这样的ICT反应，其中Phi'（ICT）/ Phi （LE）＝ 1.5，表明该反应不需要吡咯和苄腈部分的垂直扭曲。 FPP4C和PP4C在正己烷中的ICT发射带具有振动结构，但在所有其他比烷烃极性更大的溶剂中观察到无结构带。通过分析Phi'（ICT）/ Phi（LE）的温度依赖性，可以确定LE-> ICT反应在正己烷中的焓差ΔH，对于FPP4C为-11 kJ / mol，对于PP4C为-7 kJ / mol。 ）。使用这些数据，计算出由ICT排放构成的Franck-Condon基态的能量E（FC，ICT）41（FPP4C）和40 kJ / mol（PP4C）。 E（FC，ICT）的这些巨大价值得出的结论是，对于FPP4C和PP4C，不会发生绕过LE的直接ICT激励。 FPP4C的ICT偶极矩为15 D，类似于PP4C（16 D）。皮秒荧光衰减可以确定ICT寿命，从中可以得出辐射速率常数k（f）'（ICT），并且FPP4C和PP4C的值相当。这表明PP4C的ICT处于扭曲状态的论点不能来自k（f）'（ICT）。在校正了溶剂的折射率和在波浪号（max）（ICT）上的发射最大值（v）的能量后，似乎k（f）'（ICT）与溶剂的极性无关。 FPP4C和PP4C在正己烷中的飞秒瞬态吸收表明，在激发后100 fs处ICT状态已经几乎完全存在，并与LE快速平衡。在MeCN中，FPP4C和PP4C的ICT状态也同样在此延迟时间内显着发展，并且反应受到介电溶剂弛豫的限制，这表明ICT反应在实验时间限制为50 fs时超快。 PP4C和FPP4C具有相似的平面ICT结构，吡咯和苄腈亚基没有明显的扭曲。将其晶体结构与S-0基态的计算结果进行比较。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号