Chromoionophoric N2S2 macrocycles exhibiting mercury(II) selectivity

Two chromogenic N2S2-donor macrocycles functionalized with p-nitroazobenzene (L1) and phenyltricyanovinyl (L2) units were synthesized from an N-phenylated macrocyclic precursor (1) and structurally characterized by single crystal X-ray analyses. Interestingly, L1 and L2 exhibited excellent Hg2+ selectivity by showing the drastic metal-induced color change from red to colorless (Δλmax = 137 − 140 nm). The sensing ability for Hg2+ with the proposed chromoionophores is due to the stable complexation with 1:1 stoichiometry (metal-to-ligand), which was elucidated by spectrophotometry.