Control of Photoisomerization of an Azoazacryptand by Anion Binding and Cucurbituril Encapsulation in an Aqueous Solution
datasetposted on 06.07.2020, 19:38 by Aleksandr S. Oshchepkov, Siva S. R. Namashivaya, Victor N. Khrustalev, Frank Hampel, Dimitri N. Laikov, Evgeny A. Kataev
Control of isomerization of a receptor bearing multiple light-switchable subunits in a confined space is critical for the design of synthetic molecular machines. Toward this goal, a new azacryptand containing three azobenzene subunits has been developed, and its photoisomerization in an aqueous solution has been studied depending on anion coordination and recognition by a larger hostcucurbituril (CB). The cryptand in its hexaprotonated form shows considerable affinity for fluoride and perchlorate, which in turn affects the isomer distribution of the receptor under UV-light irradiation, stabilizing the isomers of the cryptand with Z-configurations. CB was found to be able to encapsulate the isomers of the cryptand by forming a Matryoshka-type complex. The irradiation of a 10:1 CB–cryptand mixture has led to a selective conversion of the cryptand to the E,E,Z isomer inside CB. It has been demonstrated that the addition of fluoride to the resulted complex induces the release of the cryptand as a major E,E,E isomer, while other studied anions were ineffective in this reaction. To our knowledge, this work presents a first example of a host-controlled photoisomerization of an anion receptor bearing multiple switching azobenzenes that model the function of naturally occurring chaperones.