Cation selectivity of ionophores based on tripodal thiazole derivatives on benzene scaffold

The synthesis and potentiometric evaluation of new 1,3,5-tris(thiazolylcarbethoxy)-2,4,6-trimethylbenzene (3), 1,3,5-tris(thiazolylhydroxy)-2,4,6-trimethylbenzene (4), 1,3,5-tris(thiazolylmethyl)-2,4,6-trimethylbenzene (5), and 1,3,5-tris(thiazolylphenyl)-2,4,6-trimethylbenzene (6), toward mono and divalent cations under various pH conditions are outlined. The ion-selective properties of the newly synthesized compounds were studied by measuring the potentiometric responses of the 3-, 4-, 5-, and 6-based membrane electrodes to alkali metal, alkaline earth metal, ammonium, and transition metal ions, under various pH conditions. The 3-based electrode exhibited a Nernstian response to ammonium and potassium under alkaline pH conditions, while the other three electrodes showed a poor potentiometric performance. All electrodes showed substantial responses to silver ion under acidic condition, but there was almost nil response to other transition metal ions (Fe²⁺, Co²⁺, Zn²⁺, Ni²⁺, Pb²⁺, Cd²⁺, Cu²⁺ and Hg²⁺). The 3- and 5-based electrodes resulted in near Nernstian responses (51.3 mV and 59.5 mV/pAg⁺, respectively) with low detection limits (100 ppt), while the 4- and 6-based ones showed sub-Nernstian below 40 mV/pAg⁺. The results were interpreted with semi-empirically modeled structures.