ESIPT and PET-based easy-to-synthesize unsymmetrical ligand in the reversible fluorimetric sensing of Al3+ and relay sensing of inorganic and biological phosphates

Abstract

We have developed an unsymmetrical Schiff-base ligand H3L which selectively senses Al3+ over all other metal ions in ethanol–water mixture (1:1). There is dramatic increase in the intensity of fluorescence on addition of Al3+ to the solution of ligand in EtOH/H2O mixture. NMR studies, HRMS results and fluorescence experiments have been conducted to confirm the binding mode of different metals with H3L. The detection limit for aluminum ion is 72.6 × 10−9 M. The L-Al3+ complex has been subsequently used to detect inorganic and organic phosphates. An “On-Off-On” relay recognition of Al3+ ion and different phosphate and pyrophosphate ions, ATP and ADP has been achieved. The probe has shown good reversibility behavior based on which truth table and logic gate was designed. Lifetime and quantum yield values have been measured in an effort to investigate the sensing ability of the ligand. Cost effective real-time detection of Al3+ has been demonstrated by filter paper strips.