Electronically tuned 1,3,5-triarylpyrazolines as Cu(i)-selectivefluorescent probes
作者:Manjusha Verma、Aneese F. Chaudhry、M. Thomas Morgan、Christoph J. Fahrni
DOI:10.1039/b918311f
日期:——
We have prepared and characterized a Cu(I)-responsive fluorescent probe, constructed using a large tetradentate, 16-membered thiazacrown ligand ([16]aneNS3) and 1,3,5-triaryl-substituted pyrazoline fluorophores. The fluorescence contrast ratio upon analyte binding, which is mainly governed by changes of the photoinduced electron transfer (PET) driving force between the ligand and fluorophore, was systematically optimized by increasing the electron withdrawing character of the 1-aryl-ring, yielding a maximum 50-fold fluorescence enhancement upon saturation with Cu(I) in methanol and a greater than 300-fold enhancement upon protonation with trifluoroacetic acid. The observed fluorescence increase was selective towards Cu(I) over a broad range of mono- and divalent transition metal cations. Previously established Hammett LFERs proved to be a valuable tool to predict two of the PET key parameters, the acceptor potential (E(A/A−) and the excited state energy ΔE00, and thus to identify a set of pyrazolines that would best match the thermodynamic requirements imposed by the donor potential E(D+/D) of the thiazacrown receptor. The described approach should be applicable for rationally designing high-contrast pyrazoline-based PET probes selective towards other metal cations.
我们制备并表征了一种响应于Cu(I)的荧光探针,该探针使用了一个大型四齿、16元环硫氮冠醚配体([16]aneNS3)和1,3,5-三芳基取代的吡唑啉荧光团。分析物结合后的荧光对比度,主要由配体与荧光团之间光诱导电子转移(PET)驱动力的变化决定,通过增加1-芳基环的电子吸引特性进行了系统优化,在甲醇中与Cu(I)饱和时可实现最大50倍的荧光增强,而在三氟醋酸质子化后可实现超过300倍的增强。所观察到的荧光增加对Cu(I)具有选择性,且在广泛的单价和二价过渡金属阳离子中表现良好。先前建立的Hammett线性自由能关系(LFER)被证明是预测PET关键参数(受体电位E(A/A−)和激发态能量ΔE00)的有价值工具,从而识别出一组最符合硫氮冠 receptor 的给体电位E(D+/D)热力学要求的吡唑啉化合物。所描述的方法应适用于合理设计针对其他金属阳离子的高对比度吡唑啉基PET探针。