Fully discuss and explicate the quite different fluorescence property and response performance to TNP between four analogous coumarin derivatives.

Coumarin derivatives are ideal scaffolds for fluorescent probes due to their excellent photophysical properties and modifiability. However, tiny structural change of molecule often caused different fluorescence performance. Here, 3-formylcoumarin and several active methylene compounds were utilized to synthesize four analogous coumarin derivatives (XS, XB, XY, XM). With the help of density functional theory (DFT) calculations and systematical experiments, the effects of structural contrast on fluorescent characteristics and AIE property were investigated thoroughly. Why their emission performance and identification ability for 2,4,6-trinitrophenol have large disparities were also precisely delineated. Accurate recognition mechanism, especially the bonding site was discussed in detail aided by DFT calculations and RDG analysis. Among them, XS had the highest fluorescent quantum yield (64.27 %) and radiative transition rate (3.61 × 108 s-1). XS also exhibited high sensitivity and excellent anti-interference ability for TNP discrimination with detection limit as low as 97.2 nM and binding constant as 2.92 × 1010 M-1.