基于激发态分子内质子转移调控的接力识别荧光探针研究

Relay recognition is a new research direction for function intensify of fluorescent probes. The objective of this project is to realize relay recognition of important metal ions and anions through modulating the excited-state intramolecular proton transfer (ESIPT) process of fluorescent probes. Based on typical ESIPT featured fluorophores such as benzoxazole, benzothiozole, benzoimidazole and 1,3,4-oxadiazole derivatives,we plan to synthesize three classes of fluorescent probes that contains different conjugative structure and substituents. By utilizing the synergistic interaction of ESIPT proton donor and receptor moiety of the the probe with a specific metal ion to realize certain metal ion recognition, the in situ generated "probe-metal ion" complex is used as an indirect probe for anion recognition via metal ion displacement approach. The ESIPT status of the probe is controled by metal ion binding and releasing processes, thus realize the relay recognition function of the probes through modulating ESIPT. Moreover, it is also necessary to clarify the effect of probe structure on ESIPT property and the structure-activity relationship between probe structure and relay recognition behavior through investigating the effects of substituents and conjugation systems on the ESIPT and relay recognition behaviors of the synthesized probes. Through exploration of the structur-property relationships, it is aimed to obtain a series of realy recognition function fluorescent probes that with long wavelength emission and ratiometric emission reponses to target ion species. These investigations will provide theoretical foundation for the design and synthesis of relay recognition fluorescent probes based on modulating ESIPT. The related results have broad applicability and significant scientific meaning in the research fields of relay recognition function fluorescent probes.

接力识别是荧光探针分子功能强化的新方向。本项目旨在通过对荧光探针的激发态分子内质子转移（ESIPT）过程的调控实现重要金属离子和阴离子的接力识别。拟以典型的具有ESIPT性质的荧光团为基本骨架，设计合成三类含不同共轭体系和取代基团的荧光探针。利用探针分子中ESIPT质子供体基团和离子识别基团的协同作用实现金属离子的识别，原位生成的"探针-金属离子"配合物通过金属离子取代实现阴离子识别；通过ESIPT的质子供体基团与金属离子的先结合后释放控制ESIPT状态，从而实现基于ESIPT调控的接力识别功能。考察不同取代基、共轭体系对探针分子的ESIPT性质及接力识别功能的影响，探索结构与性能间相关规律，力求获得系列具有长波长发射、比率荧光响应的接力识别功能荧光探针，为基于ESIPT调控的接力识别荧光探针的设计合成提供理论依据。相关结果在接力识别功能荧光探针研究方面具有广阔的应用前景和重要的科学意义。

接力识别型荧光探针可使两种离子的识别操作能在同一测试条件下连续进行，具有操作简单的显著优点，备受人们关注并成为荧光探针分子功能强化的重要方向之一。本项研究以具有激发态分子内质子转移（ESIPT）性质的苯并唑类、2,5-二芳基-1,3,4-噁二唑类荧光团为基本骨架，将ESIPT性质的调控和接力识别功能同时赋予一个荧光探针分子，设计合成了系列基于ESIPT调控的接力识别型荧光探针。通过在探针分子结构中引入特定的金属离子螯合基团，实现了对金属离子的高选择性识别，同时通过ESIPT质子供体参与金属离子螯合抑制探针的ESIPT性质。考察了原位生成的“探针-金属离子”络合物对阴离子的识别作用，实现了基于ESIPT调控的接力识别，部分探针具有长波长发射和比率荧光信号变化。考察了不同取代基、共轭体系以及识别基团对探针分子的ESIPT性质及接力识别功能的影响。对具有ESIPT性质的双荧光团类荧光探针进行了探索，已经获得的研究经验为后续研究提供了借鉴。此外，对其他具有ESIPT性质的接力识别荧光探针也进行了探索性研究，并取得了一些有意义的研究结果。通过上述研究发现：（1）延展共轭体系、取代基的类型和位置对探针发射波长的影响较为复杂，尤其是在含水介质中的发射波长规律性并不明显；（2）通过可显著增强分子内电荷转移（ICT）的方式延展ESIPT荧光团的共轭体系，是获得长波长发射ESIPT类荧光探针的有效途径；（3）荧光探针中金属离子受体单元的设计对其接力识别功能具有重要影响。本项目的研究结果可为进一步研究基于ESIPT调控的接力识别荧光探针提供较强的借鉴意义。