A chromone Schiff-base as Al(III) selective fluorescent and colorimetric chemosensor

A novel and simple chromone Schiff-base receptor 7-methoxychromone-3-carbaldehyde-(indole-2-formyl) hydrazone (MCIH) was prepared. Among the various metal ions, only Al3+ induces the fluorescence enhancement and results in “OFF-ON” type sensing with excellent selectivity and high sensitivity in ethanol system. Upon binding of Al3+, a significant fluorescence enhancement with an “OFF-ON” ratio over 500-fold was triggered and it features visible light excitation (423 nm) and emission (507 nm) profiles. However, other metal ions had no such significant effect on the fluorescence. Also, MCIH can severe as a highly selective chemodosimeter for Al3+ with “naked-eye” detection, which is easily observed from colorless to yellow-green. The detection limit of MCIH for Al3+ detection was as low as 5×10−8 M level.