A Highly Specific Ca2+-Ion Sensor: Signaling by Exciton Interaction in a Rigid-Flexible-Rigid Bichromophoric “H” Foldamer

Selective, sensitive cation capture: A bichromophoric “H”-foldamer (rigid-flexible-rigid) demonstrates a cation-steered exciton interaction (see figure; the interaction is denoted by the double-headed arrow) and thereby allows the selective signaling of Ca2+-ion binding among Na+, K+, and Mg2+ ions. The binding can be observed with the naked eye, as well as by absorption, emission, and 1H NMR spectral changes. An analogous monochromophore (flexible-rigid-flexible) failed to signal any of the binding events.