Colorimetric Chemosensor for Cu²⁺ and Fe³⁺ Based on a meso-Triphenylamine-BODIPY Derivative

Optical chemosensors are a practical tool for the detection and quantification of important analytes in biological and environmental fields, such as Cu²⁺ and Fe³⁺. To the best of our knowledge, a BODIPY derivative capable of detecting Cu²⁺ and Fe³⁺ simultaneously through a colorimetric response has not yet been described in the literature. In this work, a meso-triphenylamine-BODIPY derivative is reported for the highly selective detection of Cu²⁺ and Fe³⁺. In the preliminary chemosensing study, this compound showed a significant color change from yellow to blue-green in the presence of Cu²⁺ and Fe³⁺. With only one equivalent of cation, a change in the absorption band of the compound and the appearance of a new band around 700 nm were observed. Furthermore, only 10 equivalents of Cu²⁺/Fe³⁺ were needed to reach the absorption plateau in the UV-visible titrations. Compound 1 showed excellent sensitivity toward Cu²⁺ and Fe³⁺ detection, with LODs of 0.63 µM and 1.06 µM, respectively. The binding constant calculation indicated a strong complexation between compound 1 and Cu²⁺/Fe³⁺ ions. The ¹H and ¹⁹F NMR titrations showed that an increasing concentration of cations induced a broadening and shifting of the aromatic region peaks, as well as the disappearance of the original fluorine peaks of the BODIPY core, which suggests that the ligand-metal (1:2) interaction may occur through the triphenylamino group and the BODIPY core.