Fluoranthene-terminated terpyridine ensemble for fluorescence light up and ratiometric chemical sensor for multi...

A novel π-electron rich fluoranthene embellished with a phenyl spacer and coupled with terpyridine (TS1) was developed through Diels-Alder reaction. Single crystal X-ray structure evidences the variations in dihedral angles between the fluoranthene and the phenyl unit responsible for development of non-coplanar interactions and stabilized by a wave-like molecular packing in the crystal lattice with weak π-π interaction of 4.125 Å. The peripheral terpyridine of TS1 endows an efficient binding with multiple metal ions by colorimetric and fluorometric methods. TS1 exhibits a ratiometric fluorescence response from sky blue to yellow colour upon the addition of Zn²⁺ ions with a limit of detection (LOD) of 0.05 ppm. The other metal ions such as Cu²⁺, Co²⁺ and Fe²⁺ demonstrate fluorescence quenching behaviour with LODs of 0.1, 0.3 and 0.7 ppm, respectively. The intramolecular charge transfer (ICT) shows the variation in TS1 emission behaviour upon metal ions interaction and quantitatively discriminates the metal ion concentrations. TS1 conferred a visual colorimetric change from colourless to magenta, enabling naked-eye detection of Fe²⁺ and showing clear discrimination between Fe²⁺ and Fe³⁺ ions for the real-time water samples. Furthermore, we have investigated the effect of TS1 in Zebrafish larvae/embryos and cytotoxicity in human urinary tract transitional cell carcinoma cells (UM-UC-3).