Strong intramolecular charge-transfer effect strengthening naphthoquinone-based chemosensor: Experimental and theoretical evaluation

An aminophenol-linked naphthoquinone-based fluorometric and colorimetric chemosensor 2-chloro-3-((3-hydroxyphenyl) amino) naphthalene-1,4-dione (2CAN-Dione) was synthesized for selective detection of Sn²⁺ ion in aqueous solution. The amine and conversion of carbonyl into carboxyl groups play a vital role in the sensing mechanism when Sn²⁺ is added to 2CAN-Dione. Comprehensive characterization of the sensor was carried out using standard spectral and analytical approaches. Because of the intramolecular charge transfer (ICT) effect and the turn-on sensing mode, the strong fluorometric emission towards Sn²⁺ was observed at about 435 nm. The chemosensor exhibited good selectivity for Sn²⁺ in the presence of coexisting metal ions. An improved linear connection was established with a low limit of detection (0.167 μM). FT-IR, ¹H NMR, ¹³C NMR, and quantum chemistry methods were performed to verify the binding coordination mechanism. The chemosensing probe 2CAN-Dione was successfully employed in bioimaging investigations, demonstrating that it is a reliable fluorescent marker for Sn²⁺ in human cancer cells.