Cyclodextrin-Sandwiched Hexaphyrin Hybrids: Side-to-Side Cavity Coupling Switched by a Temperature- and Redox-Responsive Central Device.

Abstract

Access to allosteric enzyme mimics that ideally associate communicating compartments for catalysis and regulation is still challenging. Whereas a sandwich "cavity-catalyst-cavity" approach, developed mainly with cyclodextrins and porphyrins, appears promising, its counterpart with hexaphyrins featuring rich conformation, aromaticity, and coordination behavior has not been prospected at all. We thus developed sandwich hybrids made of two cyclodextrins triply linked on each side of a hexaphyrin. The latter displays switchable oxidation states with interconvertible conformations (28π antiaromatic and 26π aromatic, each adopting rectangular and dumbbell forms). These four states are connected by two orthogonal switches under redox [aromaticity] and thermal [shape] control. This leads to twin compartmentalized confined spaces either locked or unlocked depending on the conformation of the hexaphyrin, and the reversibility of the lock↔unlock transition relies on the aromaticity of the hexaphyrin. The sandwiched heteroannulene thus behaves as an unprecedented dual-responsive double-latched device. Such hybrid systems open interesting perspectives in the allosteric regulation of receptors, catalysts, and machineries.