Theoretical and experimental studies on mechanochromic triphenylamine based fluorescent “ON-OFF-ON” sensor for sequential detection of Fe3+ and deferasirox

Abstract

A novel triphenylamine (TPA) based sensor TTU was rationally designed and synthesized that exhibited reversible mechanochromic and aggregation induced emission enhancement (AIEE) properties. The AIEE active sensor was employed for fluorometric detection of Fe³⁺ in aqueous medium, with distinguished selectivity. The sensor showed a highly selective quenching response towards Fe³⁺ that is ascribed to complex formation with paramagnetic Fe³⁺. Subsequently, TTU-Fe³⁺ complex acted as a fluorescence sensor for the detection of deferasirox (DFX). The subsequent addition of DFX to TTU-Fe³⁺ complex led to the recovery of fluorescence emission intensity of sensor TTU that was attributed to the displacement of Fe³⁺ by DFX and release of sensor TTU. The proposed sensing mechanisms for Fe³⁺ and DFX was confirmed through ¹H NMR titration experiment and DFT calculations. Frontier molecular orbitals (FMO), density of states (DOS), natural bond orbital (NBO), non-covalent interaction (NCI) and electron density difference (EDD) analysis were performed using DFT calculations to support the experimental results. Moreover, sensor TTU displayed colorimetric detection of Fe³⁺. Further, the sensor was employed for the detection of Fe³⁺ and DFX in real water samples. Finally, logic gate was fabricated by using sequential detection strategy.