Closed-to-Open-Shell Molecular Sensing Enables Highly Selective Detection of Chemical Warfare Agents

Highly selective detection of chemical warfare agents (CWAs) is critical for public safety but remains extremely challenging due to the poor specificity of conventional fluorescent sensing reactions. Herein, an innovative sensing system based on a closed-to-open-shell transformation is reported. This system enables distinct and analyte-specific optical responses toward typical CWA simulants, including diethylchlorophosphate (DCP), bis(trichloromethyl) carbonate (BTC) and 2-chloroethylethyl sulfide (2-CEES), while also differentiating from the key interferent, HCl. Upon reaction with these analytes, the designed dithienylethene (DTE) derivatives generate stable luminescent radicals exhibiting clearly distinguishable fluorescence and colorimetric signatures. Mechanistic investigations reveal that the exceptional selectivity arises from the competition between Kasha- and anti-Kasha-rule radical emissions, giving each analyte a unique optical fingerprint. This work thus establishes a closed-to-open-shell sensing paradigm that integrates chemical specificity with multimodal optical response, offering a conceptual and practical advance toward selective and real-time detection of CWAs at the molecular level.