Heterocyclic Hemipiperazines: Multistimuli‐Responsive Switches and Sensors for Zinc or Cadmium Ions.

Advance in the design of molecular photoswitches ‐ adapters that convert light into changes at molecular level ‐ opens up exciting possibilities in preparing smart polymers, drugs photoactivated inside humans, or light‐fueled nanomachines that might in the future operate in our bloodstream. Hemipiperazines are recently reported biocompatible molecular photoswitches based on cyclic dipeptides. Here we report a multistimuli‐responsive hemipiperazine‐based switch that reacts on light, solvents, acidity, or metal ions. Its photoequilibration is controlled by the intramolecular hydrogen bonding pattern. The compound can be used as a mid‐nanomolar photoswitchable fluorescent sensor for zinc and cadmium ions, applicable to monitor environmental pollution in real time. [ABSTRACT FROM AUTHOR]