Design, Synthesis And Property Of Fluorescent Chemosensors Based On A Strategy Of Anion-induced Rotation-displaced H-aggregates

Cyanine dyes are a typical kind of dyes that have large molecular extinction coefficient and good fluorescence quantum yield.They have been used for the molecular design chemosensors for detection of various ions monitored by ion-induced ?uorescence changes.As known,it is significant to recognize specific anion such as HSO₄^-in biological and environmental systems.Many studies have shown that molecular sensing and bioimaging of these bulk anionic species with tetrahedral topology are extremely challenging because of their large hydration energy and highly dispersed negative charges according to the Hofmeister bias.Hence,the design and development of efficient HSO₄^-has been a subject of great research interest in recent years.This thesis was focused on the design and synthesis of probes based on the anion-induced rotation-displaced H-aggregates?ARHA?strategy.We investigated their spectroscopic properties and the influence of the dyes' nature on the ARHA behaviors by UV-visible absorption and fluorescence spectra.The details are summarized as follows:Fristly,two hemicyanine-based dyes L1,L2 which have core framework of4-hydroxylstyrylindolium moiety were synthesized.The styryl derivatives L3-L6 have also been prepared.We found that L1 and L2 exhibited a high selectivity and sensitivity for HSO₄^-ions in aqueous solution.Upon addition of HSO₄^-ions,the chemosensors present prominent enhanced hypsochromic-shifted fluorescent spectra via the ARHA fluorescent mechanism with a detection limit of HSO₄^-ions down to the ¹0-7 M scale.However,the dyes L3-L6 had no responses toward HSO₄^-under the identical conditions.Thus,the framework4-hydroxylstyrylindolium moiety turned out to be the core structure to achieve highly HSO₄^--selective fluorescent chemosensors via the ARHA strategy.Meanwhile,the good membrane permeability of chemosensor L2 is also useful for the detection of intracellular HSO₄^-ions by a fluorescence microscopy.Thus,the ARHA fluorescent mechanism for HSO₄^-ions detections is proved to be efficient in live cells.Secondly,we synthesized the compounds CH1,CH2 with benzothiazole or quinoline moiety moiety,which further confirmed our hypothesis about the core factor of ARHA strategy.The results show that CH1,CH2 have similar recognition behavior to L1,L2 towards the high concentration of HSO₄^-.More interestingly,CH1 and CH2 also showed excellent selectivity to Chs and Hep,which contained-OSO₃ H groups in the structure.The detection limits were estimated to be 2.13×10^-5 M?1.13×10^-5 M and 6.55×10^-7 M?1.99×10⁽-60M for CH1 and CH2 to Chs and Hep,respectively.In conclution,the ARHA strategy opens new routes to design of fluorescent sensors for detection of tetrahedral anionic species or biomacromolecular with similar moiety.