Reversible Anion and Ion-Pair Recognition under Electronic Control

有了这个奖项，化学系的大分子，超分子和纳米化学项目资助佛罗里达州立大学的Sourav Saha教授开发新的策略和受体，不仅可以根据其电子特性区分阴离子，而且还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。阴离子和阳离子普遍存在，并且具有不同的结构、性质和功能。有些在生物、化学、工业和环境过程中发挥重要作用，而另一些则是有毒和污染物。由于这些原因，重要的是以高精度和选择性调节这些带电物质。选择性离子受体可以为科学家提供可回收，可重复使用，更适合环境保护应用的系统。从事该项目的研究生，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。综合推广活动针对当地学校、公共图书馆和佛罗里达农业和矿业大学（HBCU机构）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实践实验，以激励他们考虑追求科学事业。本研究的目标是开发新的策略，（i）歧视阴离子的基础上，他们的电子性质，（ii）捕获阴离子和阳离子同时在合作的方式，和（iii）结合和释放离子客人在可逆的方式下的电子和光的影响。为了区分非质子溶剂中的阴离子，Saha研究小组正在利用α-酸性萘二酰亚胺（NDI）受体从强刘易斯碱性阴离子接受电子的能力，与碱性较低的阴离子形成电荷转移复合物，并参与阴离子？CH 3和CH···阴离子与电荷扩散阴离子的相互作用。为了克服削弱离子客体和受体之间的结合相互作用的离子配对效应，正在通过将两个末端NDI单元与可以结合阳离子的折叠接头拴系来开发镊子形状的双配位离子对受体。假设是阳离子结合在接头单元处应促进两个重叠NDI单元之间的阴离子结合，反之亦然。在双相萃取期间，这些双配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性介质萃取至有机介质，而较多水合硬阴离子应保留在水中。基于NDI的阳离子金属杂环正被构造成通过阴离子/NDI相互作用在其空腔内捕获大的电荷扩散阴离子。金属离子角应减轻离子配对效应。NDI单元的可逆氧化还原化学及其还原形式排出阴离子的趋势提供了一种新的方法，以在化学、电化学和/或光化学还原时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.