Visible-Light Responsive Sucrose-Containing Macrocyclic Host for Cations

Abstract

Chiral photoresponsive host <b>1</b> was prepared by a high-yield Cs₂CO₃-templated macrocyclization. <i>Trans</i>-<b>1</b> transforms into long-lived <i>cis</i>-<b>1</b> (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 <i>cis</i>-<b>1</b> binds cations stronger than <i>trans</i>-<b>1</b> (<i>K_cis</i>/<i>K_trans</i> ≤ 4.1). ¹H NMR titration experiments as well as density functional theory studies reveal that sucrose ring oxygen residues and azobenzene nitrogen atoms in <b>1</b> contribute to cation coordination.