Aza- and Mixed Thia/Aza-Macrocyclic Receptors with Quinoline-Bearing Pendant Arms for Optical Discrimination of Zinc(II) or Cadmium(II) Ions.

The synthesis and coordination properties of two fluorescent chemosensors, featuring [9]aneN (1,4,7-triazacyclononane; L1) and [12]aneNS (1-aza-4,7,10-trithiacyclododecane; L2) as receptor units, and a quinoline pendant arm with an amide group as a functional group spacer are described. The optical responses of L1 and L2 in the presence of several metal ions were analysed in MeCN/H O (1 : 4 v/v) solutions. A selective chelation enhancement of fluorescence (CHEF) effect was observed in the presence of Zn in the case of L1, and in the presence of Cd in the case of L2, following the formation of a 1 : 1 and a 1 : 2 metal/ligand complex, respectively, which was also confirmed by potentiometric measurements. H and C NMR measurements in CD CN/CDCl in combination with molecular mechanics calculations show that for both complexes of L1 and L2 with Zn and Cd , respectively, the coordination of the carbonyl group from the pendant arm could be the origin of the observed optical selectivity.