Fluorescent switches based on spirocyclic zwitterionic Meisenheimer (SZMC) complexes are stimuli-responsive organic molecules with application in a variety of areas. To expand their functionality, novel switching mechanisms are herein reported for these systems: (a) acid- and redox-triggered formation of an additional protonation state with distinct optical properties, and (b) solvent-induced fluorescence modulation. We demonstrate that these new features, which enable both multistimuli and multistate operation of SZMC switches, can be exploited in the preparation of smart organic materials: wide-range pH optical probes, electrochromic and electrofluorochromic films, and polymer-based fluorescent detectors of organic liquids.

Stable zwitterionic spirocyclic Meisenheimer compounds were synthesized using a one-step reaction between picric acid and diisopropyl (ZW1) or dicyclohexyl (ZW3) carbodiimide. A solution of these compounds displays intense orange fluorescence upon UV or visible light excitation, which can be quenched or “turned-off” by adding a mole equivalent amount of F− or CN− ions in acetonitrile. Fluorescence is not quenched in the presence of other ions such as Cl−, Br−, I−, NO2−, NO3−, or H2PO4−. These compounds can therefore be utilized as practical colorimetric and fluorescent probes for monitoring the presence of F− or CN− anions.

The control of chemical functionalization with orthogonal light stimuli paves the way toward manipulating materials with unprecedented spatiotemporal resolution. To reach this goal, we herein introduce a photochemical reaction system that enables two-color control of covalent ligation via an oxo-Diels−Alder cycloaddition between two separate lightresponsive molecular entities: a UV-activated photocaged diene based on ortho-quinodimethanes and a carbonyl dienophile appended to a diarylethene photoswitch, whose reactivity can be modulated upon illumination with UV and visible light.

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A multi‐responsive photo and electrochromic salt based on a viologen derivative ([(C10)2Bpy]2+) as organic cation combined with diarylethene anion ([DTE]2−) is synthesized and characterized for the first time. The coloration of this functional salt can be modulated by light and electricity according to further applications. Photochemical determination of the quantum yields in solution for the ring‐opening and closure of [(C10)2Bpy][DTE‐COO] ionic liquid have been determined. The electrochemical and electrochromism performance have been also studied in order to evaluate the reduction of bipyridinium cation as well as the oxidation of the DTE anion in its open and closed forms. The possibility of individually addressing the redox state of the anion and cation is seen as a very attractive approach to designing photo‐electrochromic devices.