Reversible Anion and Ion-Pair Recognition under Electronic Control

化学系的大分子、超分子和纳米化学项目获得这一奖项，资助佛罗里达州立大学的Sourav Saha教授开发新的策略和受体，不仅可以根据阴离子的电子性质区分它们，而且可以在电子和光的影响下以可逆的方式捕获和释放目标阴离子。阴阳离子无处不在，具有不同的结构、性质和功能。其中一些在生物、化学、工业和环境过程中发挥着重要作用，而另一些则是有毒和污染物。由于这些原因，对这些带电物种进行高精度和高选择性的调控是很重要的。选择性离子受体可以为科学家提供可回收、可重复使用的系统，更适合于环境保护应用。从事这个项目的研究生、本科生和博士后研究人员将获得从合成到分子识别的一系列科学知识和技术专长。综合外展活动针对当地学校、公共图书馆以及HBCU下属机构佛罗里达农业和矿业大学的学生。通过这些努力，萨哈博士计划让年轻和代表性不足的学生参与动手实验，以激励他们考虑在科学领域追求职业。这项研究的目标是开发新的策略来(I)根据阴离子的电子性质来区分它们，(Ii)以合作的方式同时捕获阴离子和阳离子，以及(Iii)在电子和光的影响下以可逆的方式结合和释放离子客体。为了区分非质子性溶剂中的阴离子，SAHA研究小组正在利用强酸性萘二亚胺受体接受来自强Lewis碱性阴离子的电子(S)的能力，与较少的碱性阴离子形成电荷转移络合物，并与电荷扩散阴离子进行阴离子和CH····阴离子相互作用。为了克服削弱离子客体和受体之间结合相互作用的离子配对效应，通过将两个末端NDI单元与可以结合阳离子的折叠连接物连接起来，正在开发镊子形状的重复离子对受体。假设连接单元上的阳离子结合应该促进两个重叠的NDI单元之间的阴离子结合，反之亦然。在两相萃取过程中，这些双位受体应选择性地将含有较少水合电荷扩散阴离子的盐从水介质中提取到有机介质中，而较多水合的硬阴离子应留在水中。人们正在构建基于NDI的阳离子金属环，以通过阴离子/NDI相互作用在其腔内捕获大量电荷扩散的阴离子。金属离子转角应能缓解离子配对效应。NDI单元的可逆氧化还原化学和它们的还原形式驱逐阴离子的趋势提供了一种新的方法，通过化学、电化学和/或光化学还原从这些受体释放捕获的阴离子。

With this award, the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry is funding Professor Sourav Saha of Florida State University to develop new strategies and receptors that can not only discriminate anions on the basis of their electronic properties, but also capture and release the target anions in a reversible fashion under the influence of electrons and light. Anions and cations are ubiquitous, and have diverse structures, properties, and functions. Some play important roles in biological, chemical, industrial, and environmental processes, while others are toxic and pollutants. For these reasons, it is important to regulate these charged species with high precision and selectivity. Selective ion receptors can provide scientists with systems that are recyclable, reusable, and better suited for applications in environmental protection. The graduate, undergraduate, and postdoctoral researchers working on this project will gain an array of scientific knowledge and technical expertise, from synthesis to molecular recognition. Integrated outreach activities are directed at local schools, the public library, and at students from Florida Agricultural and Mining University, an HBCU institution. Through these efforts, Dr. Saha plans to engage young and underrepresented students in hands-on experiments to motivate them to consider the pursuit of careers in science. The goal of this research is to develop new strategies to (i) discriminate anions on the basis of their electronic properties, (ii) capture anions and cations simultaneously in a cooperative fashion, and (iii) bind and release ionic guests in a reversible fashion under the influence of electrons and light. To discriminate anions in aprotic solvents, the Saha research team is exploiting the ability of ð-acidic naphthalenediimide (NDI) receptors to accept electron(s) from strong Lewis basic anions, form charge-transfer complexes with less basic anions, and engage in anion?ð and CH···anion interactions with charge-diffuse anions. To overcome the ion-pairing effect that weakens the binding interactions between ionic guests and receptors, tweezers-shaped, ditopic ion-pair receptors are being developed by tethering two terminal NDI units with folded linkers that can bind cations. The hypothesis is that cation binding at the linker units should facilitate anion binding between the two overlapping NDI units and vice versa. During biphasic extractions, these ditopic receptors should selectively extract salts that contain less hydrated charge-diffuse anions from aqueous to organic medium, while the more hydrated hard anions should remain in water. NDI-based cationic metallacycles are being constructed to capture large charge-diffuse anions inside their cavities through anion/NDI interactions. The metal ion corners should mitigate the ion-pairing effects. The reversible redox chemistry of the NDI units and the tendency of their reduced forms to expel anions offer a new approach to release the captured anions from these receptors upon chemical, electrochemical, and/or photochemical reduction.