Visible-Light Responsive Sucrose-Containing Macrocyclic Host for Cations

Abstract

Chiral photoresponsive host 1 was prepared by a high-yield Cs2CO3-templated macrocyclization. Trans-1 transforms into long-lived cis-1 (25 days) upon irradiation with green light, and the backward transformation is triggered by blue light. Both isomers prefer potassium among alkali metal cations, and cis-1 binds cations stronger than trans-1 (Kcis/Ktrans ≤ 4.1). 1H NMR titration experiments as well as density functional theory studies reveal that sucrose ring oxygen residues and azobenzene nitrogen atoms in 1 contribute to cation coordination.