Turn-on fluorescence sensors based on dynamic intramolecular N→B-coordination
Turn-on fluorescence sensors based on dynamic intramolecular N→B-coordination
复制标题
DOI：
10.1039/d0qo00267d
复制
发表时间：
2020-06
影响因子：
5.4
通讯作者：
Raphael Koch;Yu Sun;A. Orthaber;A. Pierik;F. Pammer
中科院分区：
文献类型：
--
作者：
Raphael Koch;Yu Sun;A. Orthaber;A. Pierik;F. Pammer
通过1，3-偶极环加成反应，合成了十个含BMes2-基团的芳基三氮唑功能化的硼烷，它们能够形成分子内五元N-→-B配位的杂环。在化合物的外围引入了从4-N-甲基-2-苯基(4-NMe2)和4-甲基苯基(4-OME)到4-氰基苯基(4-CN)、4-硝基苯基(4-NO2)和五氟苯基(C6F5)等不同的电子取代基，系统地改变了它们的电子性质和N-→B配位的强度。实验和计算研究表明，在封闭的N-→-B配位构象和两种非配位构象(Opensyn和Openanti)之间，硼烷处于动态平衡状态。对它们的结构、光学和电化学性质进行了表征，并测试了它们与亲核阴离子的结合亲和力。单独的硼烷在阴离子配位时表现出荧光猝灭(4-Me，4-OMe)或荧光开启(4-CN，4-CF3，C6F5，3，5-(CF3)2)。进一步的分析表明，与氰化物的结合亲和力可以通过改变外围取代基来调节，从5.79(±0.11)(4-Me)到6.53(±0.15)(4-CN-取代的硼烷)。这些实验数据与计算的阴离子结合亲和力相关，这表明在硼上的有效Lewis酸度覆盖了从母体化合物PhBMes2到更具Lewis酸性的PH3b的范围。
A series of ten aryl-triazole-functionalized boranes bearing BMes2-groups and capable of forming intramolecular five-membered N→B-coordinated heterocycles, has been prepared by 1,3-dipolar cycloaddition. Electronically diverse substituents ranging from 4-NMe2-phenyl (4-NMe2) and 4-OMe-phenyl (4-OMe) to 4-cyanophenyl (4-CN), 4-nitrophenyl (4-NO2) and pentafluorophenyl (C6F5) have been introduced in the periphery of the compounds to systematically vary their electronic properties and the strength of the N→B-coordination. Experimental and computational studies show that the boranes exist in dynamic equilibrium between a closed N→B-coordinated conformation and two types of non-coordinated conformations (opensyn and openanti). Their structural, optical and electrochemical properties have been characterized, and their binding affinities for nucleophilic anions has been tested. Individual boranes exhibit either fluorescence quenching (4-Me, 4-OMe) or fluorescence turn-on (4-CN, 4-CF3, C6F5, 3,5-(CF3)2) upon coordination of anions. Further analyses show that the binding affinity to cyanide can be tailored through variation of the peripheral substituent, ranging from 5.79 (±0.11) for 4-Me to 6.53 (±0.15) for the 4-CN-substituted borane. These experimental data correlate with computed anion binding affinities, which indicate that the effective Lewis acidity at boron covers a range reaching from the parent compound PhBMes2 to the much more Lewis acidic Ph3B.