Colorimetric and fluorescent chemosensors for the detection of 2,4,6-trinitrophenol and investigation of their co-crystal structures.

A full account of our studies of 2,4,6-trinitrophenol (TNP) sensing is provided. A series of chemosensors with a variety of aromatic chromophores for specific recognition of TNP has been designed and then realized through the fluorescence "on/off" mechanism. These chemosensors demonstrated highly selective, sensitive, and fluorescent quenching of TNP with remarkable visual changes through the intramolecular charge-transfer (ICT) process. Their host-guest interactions were investigated by (1)H NMR spectroscopic titrations and their corresponding co-crystal structures, which showed that the 1:1 host-guest complexes were formed by multiple hydrogen-bond interactions in solution or in the solid state. The origins of the significant affinity demonstrated during the fluorescence recognition process were further disclosed through DFT calculations of corresponding compounds.