Intermolecular C–H⋯O hydrogen bond–induced H-aggregates for rapid, real-time detection of cyanide

A specialized chemodosimeter, H1, incorporates a solid red fluorophore formed using a nearly planar dimethylaniline–indanedione conjugate, leveraging an intramolecular charge transfer (ICT) mechanism engineered for cyanide detection. Chemodosimeter H1 exhibits strong ICT-induced emission in polar organic solvents, although its fluorescence diminishes in the solid state. Compared with the J-aggregated solid red fluorophore J1, which has a similar dimethylaniline–indanedione conjugate structure, chemodosimeter H1, with an extended vinyl conjugation, displays a relatively weak and blue-shifted red emission in the solid state because of formation of H-aggregates induced by intermolecular C–H⋯O hydrogen bonds. Binding between cyanide and chemodosimeter H1 results in color and emission changes for the latter, resulting in formation of a highly twisted structure, denoted as H1–CN, which subsequently impedes ICT. Furthermore, test strips employing the H-aggregated red fluorophore H1 present a promising approach for quantitative and rapid detection of cyanide (CN⁻). These results provide a new approach to designing solid red fluorophores based on H-aggregation for CN⁻ detection.