Charge Transfer Based Colorimetric Detection of Silver Ion

Abstract

Donor–acceptor interactions or charge transfer (CT) interactions are an important class of non-covalent interactions and have been widely exploited in self-assembling systems. Beyond molecular chemistry, supramolecular chemistry aims at constituting highly complex, functional chemical systems from components held together by intermolecular forces. Chemosensors are the molecules of abiotic origin that bind selectively and reversibly with the analyte with concomitant change in one or more properties of the system. The recognition and signaling of ionic and neutral species of varying complexity is one of the most intensively studied areas of contemporary supramolecular chemistry. Among different types of chemosensors, colorimetric/chromogenic chemosensors are especially attractive because the guest determination can be carried out by the naked eye, without the use of expensive equipment and they also find direct applications in the development of optodes and disposable dip-stick arrays based on absorption changes. Although molecules containing an electron donor and an electron acceptor linked by a spacer have also been studied extensively in conjunction with the development of stable intramolecular CT complex, to the best of our knowledge, there is no report to sense the analyte using molecules containing an electron donor and an electron acceptor linked by a spacer. In continuation with our research on the selfassembling supramolecular systems via donor–acceptor interactions, we were intrigued to apply this interaction for signaling of ionic species. Herein we report on the design and synthesis of U-shape molecule which is linked by oligoethylene glycols (OEGs) between an electron-deficient (methyl viologen; MV) and an electron-rich (2,6-dialkoxynaphthalene; Np) units and their application on sensing metal ion (Figure 1).