Manipulating the Isomerization of a Tris-azobenzene Cage by Anion Binding

Here, we report a <i>C</i>₃-symmetric tris-azobenzene cage <b>1</b> comprising azobenzene cores and bis(urea) units. This system demonstrates efficient reversible photoisomerization and unprecedented anion-mediated switching modes. Specifically, the phosphate anion induces a concerted <i>ZZZ</i> → <i>EEE</i> isomerization with prolonged thermal relaxation (<i>t</i>_1/2 = 37.5 h at 298 K). In contrast, the bulky benzene-1,3,5-tricarboxylate anion enforces a stepwise pathway (<i>ZZZ</i> → <i>EZZ</i> → <i>EEZ</i> → <i>EEE</i>) with rapid thermal relaxation (<i>t</i>_1/2 = 54.4, 44.5, and 12.9 min for each step). This study represents the first demonstration of selective control over stepwise and concerted multi-azobenzene switch, mimicking biological adaptability through environmental changes.