pH‐Controllable Supramolecular Systems

Proton, all that matters! This Focus Review surveys representative examples of pH‐controllable supramolecular systems with interesting features and state‐of‐the‐art applications, which can lead to the construction of meaningful molecular machines for electronic and biological applications that can be controlled by simple perturbation with acid and base. magnified image This Focus Review surveys representative examples of pH‐controllable supramolecular systems with interesting features and state‐of‐the‐art applications such as 1) conformational changes within individual molecules; 2) folding/unfolding of polymers; 3) simultaneous binding of cations and anions; 4) logic function; 5) ON–OFF switchable colorimetric sensing; 6) translocation of macrocycle‐in‐rotaxane molecules; 7) large‐scale movement within molecules; and 8) regulation of the substrate flow in nanocontainers. In particular, systems will be discussed that involve: pH‐induced conformational changes of a resorcinarene cavitand and a bis(iron porphyrin) complex; pH control in assembly and disassembly of supramolecular systems stabilized with different major noncovalent interactions; pH‐driven movements of interlocked molecules involving rotaxanes, molecular elevators, and molecular muscles; and, finally, multicomponent supramolecular systems immobilized on solid supports as pH‐responsive nanovalves for the controlled release of specific substrates. Recent advances in the understanding of pH‐controllable supramolecular systems have led to the construction of meaningful molecular machines for electronic and biological applications that are amenable to control by simple perturbation with acids and bases.