Solvent viscosity tuned highly selective NIR and ratiometric fluorescent sensing of Fe3+ by a symmetric chalcone analogue.

The present communication outlined for the first time a novel combination of chromogenic near-infrared (NIR) and ratiometric fluorescence responses for Fe(3+) by a symmetric chalcone analogue (receptor 1). The key step behind NIR chromogenic response was attributed to chelation of Fe(3+) with receptor 1 upon its unfolding in aprotic, low viscosity solvents. The receptor 1 also exhibited Fe(3+) selective ratiometric changes at 538 nm and 463 nm. The chromogenic detection limit of the receptor 1 for Fe(3+) is the lowest ever (5.8 × 10(-8) M). The mechanistic details of NIR/fluorescence sensing of receptor 1 along with its solvent dependency have been discussed in detail.