Multi-Stimuli-Responsive Luminescent Ruthenium(II) Complexes as a Selective Sensor for Cyanide Detection in Aqueous...

Nowadays, various synthetic strategies are considered to develop functional materials whose properties can be adjusted in response to external stimuli such as light, pH, and chemical species. This serves as an essential step in enhancing the performance and applicability of these materials. In light of this, we reported here two luminescent ruthenium complexes based on mixed terpyridine-bipyridine ligands, represented as [Ru(L)(4,4^/-dmbpy)(pz)](ClO₄)₂ [1] and [Ru(L)(4,4^/-dmbpy)(1Mepz)](ClO₄)₂ [2], where L = 4^/-(p-tolyl)-2,2^/:6^/,2^//-terpyridine, 4,4^/-dmbpy = 4,4^/-dimethyl-2,2^/-dipyridyl, pz = pyrazole, and 1Mepz = 1-methylpyrazole. Both metal complexes have been characterized through single-crystal X-ray diffraction and other spectroscopic techniques. These complexes exhibit strong luminescence characteristics at room temperature. By utilizing the structural features, we examined their multistimulus-sensitive behavior in the presence of anionic guests, temperature changes, and light. Optical and redox characteristics were finely tuned in the presence of those stimuli. Furthermore, capitalizing on the acidic -NH proton in 1, we explored the anion-sensing capabilities in both organic and aqueous environments. Due to the absence of an -NH proton in complex 2, it does not exhibit an anion-sensing phenomenon. Complex 1 can selectively detect CN^- in a water medium down to a concentration of 10^-6 M. Job's plot and density functional theory analysis were carried out to support the anion binding mechanism.