Click Chemistry\nDerived Hexa-ferrocenylated 1,3,5-Triphenylbenzene\nfor the Detection of Divalent Transition Metal Cations

The 1,3-dipolar cycloaddition reaction (click chemistry\napproach)\nwas employed to create a hexa-ferrocenylated 1,3,5-triphenylbenzene\nderivative. Leveraging the presence of metal-chelating sites associated\nwith 1,2,3-triazole moieties and 1,4-dinitrogen systems (ethylenediamine-like),\nas well as tridentate chelating sites (1,4,7-trinitrogen, diethylene\ntriamine-like) systems, the application of this molecule as a chemosensor\nfor divalent transition metal cations was investigated. The interactions\nwere probed voltammetrically and spectrofluorimetrically against seven\nselected cations: iron(II) (Fe<sup>2+</sup>), cobalt(II) (Co<sup>2+</sup>), nickel(II) (Ni<sup>2+</sup>), copper(II) (Cu<sup>2+</sup>), zinc(II)\n(Zn<sup>2+</sup>), cadmium(II) (Cd<sup>2+</sup>), and manganese(II)\n(Mn<sup>2+</sup>). Electrochemical assays revealed good detection\nproperties, with very low limits of detection (LOD), for Co<sup>2+</sup>, Cu<sup>2+</sup>, and Cd<sup>2+</sup> in aqueous solution (0.03–0.09\nμM). Emission spectroscopy experiments demonstrated that the\ntitle compound exhibited versatile detection properties in solution,\nspecifically turn-off fluorescence behavior upon the addition of each\ntested transition metal cation. The systems were characterized by\nsatisfactory Stern–Volmer constant values (10<sup>5</sup>–10<sup>6</sup> M<sup>–1</sup>) and low LOD, especially for Zn<sup>2+</sup> and Co<sup>2+</sup> (at the nanomolar concentration level).