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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Diphenylhexatrienes as Photoprotective Agents for Ultrasensitive Fluorescence Detection
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Diphenylhexatrienes as Photoprotective Agents for Ultrasensitive Fluorescence Detection

机译：二苯基己三烯作为用于超灵敏荧光检测的光保护剂

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摘要

Given the particular importance of dye photostability for single-molecule investigations, fluorescence fluctuation spectroscopy, and laser-scanning microscopy, refined strategies were explored for enhancing the fluorescence signal by selectively quenching the first excited triplet state of the laser dye Rhodamine 123 (Rh123). The strategy is to quench the T1 state by Dexter triplet energy transfer, while undesired quenching of the singlet state via Forster or Dexter singlet energy transfer and the generation of free radicals through electron transfer should be avoided. Diphenylhexatrienes (DPHs) were tested in ethanol for their beneficial effects as a novel class of photoprotective agents using fluorescence correlationspectroscopy. A library of DPHs with electron-donating (dimethlyamino) and withdrawing substituents (e.g., trifluormethyl) was synthesized to optimize the electronic properties. Quantum chemical calculations, optical spectroscopy, and cyclic voltammetry were used to determine the electronic properties. The computed T1 emission energy of Rh123 and the T1 excitation energies of all DPHs allow for exergonic triplet energy transfer to the quencher. The parent compound quenches the T1 state of Rh123 nearly diffusion controlled (4.9 × 109 M-1 s-1). All electron-deficient DPHs significantly increase (3×) the fluorescence rate of Rh123 by reducing the triplet state population and by avoiding the formation of other long-lived dark radical states. The quenching constants are reduced by more than a factor of 2, if substituents with increasing size or electronegativity are introduced. The beneficial effect of triplet quenching of substituted DPHs is governed by a delicate interplay of steric, electronic, and intermolecular Coulombic effects.
机译：考虑到染料光稳定性对于单分子研究，荧光波动光谱和激光扫描显微镜特别重要，人们探索了精细的策略，通过选择性地淬灭激光染料若丹明123（Rh123）的第一个激发三重态来增强荧光信号。该策略是通过Dexter三重态能量转移淬灭T1状态，同时应避免通过Forster或Dexter单重态能量转移对单峰态进行不期望的淬灭以及通过电子转移产生自由基。使用荧光相关光谱法在乙醇中测试了二苯己三烯（DPHs）作为一类新型的光保护剂的有益作用。合成了具有给电子（二甲基氨基）和吸收性取代基（例如三氟甲基）的DPH库以优化电子性能。量子化学计算，光谱学和循环伏安法被用来确定电子性能。计算出的Rh123的T1发射能量和所有DPH的T1激发能都将能动三重态能量转移至淬灭剂。母体化合物淬灭了几乎受扩散控制的Rh123的T1态（4.9×109 M-1 s-1）。所有电子不足的DPH都通过减少三重态态种群并避免形成其他长寿命的暗基态来显着提高Rh123的荧光率（3倍）。如果引入具有增加的尺寸或电负性的取代基，则淬灭常数降低超过2倍。取代的DPH的三重猝灭的有益作用受空间，电子和分子间库伦效应的微弱相互作用控制。

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