Predicting the photoinduced electron transfer thermodynamics in polyfluorinated 1,3,5-triarylpyrazolines based on multiple linear free energy relationships
作者:Manjusha Verma、Aneese F. Chaudhry、Christoph J. Fahrni
DOI:10.1039/b821042j
日期:——
The photophysical properties of 1,3,5-triarylpyrazolines are strongly influenced by the nature and position of substituents attached to the aryl-rings, rendering this fluorophore platform well suited for the design of fluorescent probes utilizing a photoinduced electron transfer (PET) switching mechanism. To explore the tunability of two key parameters that govern the PET thermodynamics, the excited state energy ΔE00 and the acceptor potential E(A/A−), a library of polyfluoro-substituted 1,3-diaryl-5-phenyl-pyrazolines was synthesized and characterized. The observed trends for the PET parameters were effectively captured through multiple Hammett linear free energy relationships (LFER) using a set of independent substituent constants for each of the two aryl rings. Given the lack of experimental Hammett constants for polyfluoro-substituted aromatics, theoretically derived constants based on the electrostatic potential at the nucleus (EPN) of carbon atoms were employed as quantum chemical descriptors. The performance of the LFER was evaluated with a set of compounds that were not included in the training set, yielding a mean unsigned error of 0.05 eV for the prediction of the combined PET parameters. The outlined LFER approach should be well suited for designing and optimizing the performance of cation-responsive 1,3,5-triarylpyrazolines.
1,3,5-三芳基吡唑啉的光物理特性受到附着在芳环上的取代基的性质和位置的强烈影响,使得这一荧光基团平台非常适合设计利用光诱导电子转移(PET)开关机制的荧光探针。为了探索控制PET热力学的两个关键参数的可调性,即激发态能量ΔE00和受体电势E(A/A−),研究人员合成并表征了一系列多氟取代的1,3-二芳基-5-苯基-吡唑啉。通过对每个芳环使用一组独立的取代基常数,观察到的PET参数趋势可以通过多个Hammett线性自由能关系(LFER)有效捕捉。由于缺乏多氟取代芳香族化合物的实验Hammett常数,研究人员使用基于碳原子核电势(EPN)理论推导出的常数作为量子化学描述符。用一组不包括在训练集中的化合物评估LFER的性能,预测的结合PET参数的平均无符号误差为0.05 eV。所述的LFER方法非常适合设计和优化阳离子响应的1,3,5-三芳基吡唑啉的性能。