Organic luminescent radical-based film probes with reversible doublet state switching for ultrasensitive nerve agents simulant vapor detection

Donor-acceptor (D-A) type organic luminescent materials with intramolecular charge transfer (ICT) mechanism constitute a significant class of fluorescent probes for nerve agents sensing. However, blue-shifted emissions from nerve agents due to the protonation on donor moieties of the probes are still rarely studied and reported so far. Herein, by incorporation of high luminescence and photostability open-shell organic radicals with proton-responsive characteristics, for the first time, we report two D-A type radical-based probes, which enable high sensitivity, selectivity and good reusability nerve agents simulant (diethyl chlorophosphite, DCP) vapor detection via an uncommon blue-shift emission response. Specifically, the sensing mechanism is ultimately deciphered to be the DCP induced protonation of the donor of the radicals, whereas present fully reversal D-A electronic structure models and the nature of the doublet excited states. This sensing system offers new insights into the rational design and utility of luminescent radicals for more broad applications.