Recognition of Cu²⁺ and Al³⁺ by a Quinolinyl 1,2,3-Triazole Chemosensor: A Comparative Study

1,2,3-Triazole units with their structural and photophysical properties are well-suited for the development of chemosensors for ion sensing. Synthetic approaches make it extremely easy to modify this core with just a few steps to control ion selectivity and response-signal output. The current study examines how 8-(4-phenyl-1H-1,2,3-triazol-1-yl)quinoline, a quinoline-triazole-phenyl (QTP) construct, responds differentially to Cu²⁺ and Al³⁺ ions. QTP provides distinct fluorescent signals in acetonitrile in the presence of Cu²⁺ versus Al³⁺, a turn-off response with Cu²⁺ and blue-to-green output with Al³⁺. Spectroscopic studies quantify the selectivity of the sensor for these species with respect to other ions and reveal a stoichiometric ratio of 1:1 for sensor:Cu²⁺ and 2:1 for sensor:Al³⁺. NMR titration studies suggest that Cu²⁺ is detected via coordination of the quinolinyl and triazolyl nitrogens, while Al³⁺ is detected through coordination of the quinoline nitrogen. Overall, QTP displays a selectivity for Al³⁺ relative to Cu²⁺ over other cations in this investigation.