Triarylamine‐Bonded Binaphthyl Derivatives as Fluorescence Quenching Probes for Fe3+: An Insight into the Mechanism Based on A Single Binding Site

Abstract Triphenylamine (TPA) and binaphthyl (BINAP) have been widely used as building blocks in optoelectronics materials for their good electron donating and transport capability. However, TPA‐bonded BINAP type of fluorescent probe towards Fe 3+ , a kind of important metal ion, has not been studied. Herein, a series of TPA‐bonded BINAP D−A‐D type derivatives, 6,6‐TB‐1, 6,6‐TB‐2, 7,7‐TB‐1, 7,7‐TB‐2, and 7,7‐OMeTB‐1, was synthesized to investigate their fluorescence (FL) chemosensor properties and electronic effect on sensitivity. Results showed that these probes exhibited highly selective FL quenching toward Fe 3+ in the presence of other common metal ions, and an enhanced sensitivity (limit of detection 1.7×10 −7 M) not inferior to that of other works, could be achieved by introducing electron‐donating substituent into TPA group. Then, comprehensive studies, such as NMR, EPR, MALDI‐TOF‐MS, and XPS combined with Mulliken atomic charges analysis were performed to gain an insight into the probe's binding with Fe 3+ to understand the detection mechanism. Compared with other works on TPA‐based fluorescent probes ascribed to fluorescence resonance energy transfer (FRET) or charge transfer (CT) mechanism, we reveal the interaction between Fe 3+ and N atom of TPA and the formation of probe‐Fe 3+ complex leading to FL quenching. This work provides a simple strategy for designing a cost‐effective Fe 3+ fluorescent probe based on a single binding site to target one specific analyte.