Exploratory studies on azido-bridged complexes (Ni2+ and Mn2+) as dual colourimetric chemosensors for S2− and Ag+: combined experimental and theoretical outcomes with real field applications

Abstract

We report two isostructural dinuclear transition metal complexes [M₂(HL)₂(N₃)₄], where M = Ni²⁺ (BS-1), Mn²⁺ (BS-2), and HL is (2-methyl-2-((pyridin-2-ylmethyl)amino)propan-1-ol) and investigate them as molecular sensors towards hazardous entities. BS-1 shows high selectivity towards the S²⁻ and Ag⁺ ions, easily observed by the naked eye colour change and its detection limit in aqueous solutions for the S²⁻ ion was calculated as 0.55 μM with a binding constant of 3.28 × 10⁵ M⁻¹, while the limit for the Ag⁺ ion is 21.8 μM. Notably, BS-2 shows good selectivity towards the Ag⁺ ion with a detection limit of 10.84 μM. Spectroscopic and DFT studies shed light on the mechanistic course of interaction between the host and guest entities, suggesting a sulphide-mediated reduction of the azide mechanism. In a nutshell, these simple transition metal complexes were exploited for discriminately detecting hazardous analytes with real field applications in analytical science (via. “Dip-Stick” approach) as well as engineering science, which provides a significant contribution in the recent advancement of supramolecular chemistry.