Cation-Selective and Anion-Controlled Fluorogenic Behaviors of a Benzothiazole-Attached Macrocycle That Correlate with Structural Coordination Modes

We report how the metal cation and its counteranions cooperate in the complexation-based macrocyclic chemosensor to monitor the target metal ion via the specific coordination modes. The benzothiazolyl group bearing NO2S2-macrocycle L was synthesized, and its mercury­(II) selectivity (for perchlorate salt) as a dual-probe channel (UV–vis and fluorescence) chemosensor exhibiting the largest blue shift and the fluorescence turn-off was observed. In the mercury­(II) sensing with different anions, except ClO4– and NO3–, no responses for mercury­(II) were observed with other anions such as Cl–, Br–, I–, SCN–, OAc–, and SO42–. A crystallographic approach for the mononuclear mercury­(II) perchlorate complex [Hg­(L)­(ClO4)2]·0.67CH2Cl2 (1) and polymeric mercury­(II) iodide complex [Hg­(L)­I2]n (2) revealed that the observed anion-controlled mercury­(II) sensing in the fluorescence mainly stems from the endo- and exocoordination modes, depending on the anion coordinating ability, which induces either the Hg–Ntert bond formation or not. The detailed complexation process with mercury­(II) perchlorate associated with the cation sensing was also monitored with the titration methods by UV–vis, fluorescence spectroscopy, and cold-spray ionization mass spectrometry.