Click Chemistry Derived Hexa-ferrocenylated 1,3,5-Triphenylbenzene for the Detection of Divalent Transition Metal Cations

The 1,3-dipolar cycloaddition reaction (click chemistry approach) was employed to create a hexa-ferrocenylated 1,3,5-triphenylbenzene derivative. Leveraging the presence of metal-chelating sites associated with 1,2,3-triazole moieties and 1,4-dinitrogen systems (ethylenediamine-like), as well as tridentate chelating sites (1,4,7-trinitrogen, diethylene triamine-like) systems, the application of this molecule as a chemosensor for divalent transition metal cations was investigated. The interactions were probed voltammetrically and spectrofluorimetrically against seven selected cations: iron(II) (Fe²⁺), cobalt(II) (Co²⁺), nickel(II) (Ni²⁺), copper(II) (Cu²⁺), zinc(II) (Zn²⁺), cadmium(II) (Cd²⁺), and manganese(II) (Mn²⁺). Electrochemical assays revealed good detection properties, with very low limits of detection (LOD), for Co²⁺, Cu²⁺, and Cd²⁺ in aqueous solution (0.03-0.09 μM). Emission spectroscopy experiments demonstrated that the title compound exhibited versatile detection properties in solution, specifically turn-off fluorescence behavior upon the addition of each tested transition metal cation. The systems were characterized by satisfactory Stern-Volmer constant values (10⁵-10⁶ M^-1) and low LOD, especially for Zn²⁺ and Co²⁺ (at the nanomolar concentration level).