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(3)(1,4,7-triazacyclononane;L1) and [12]aneNS(3)(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 ofL1andL2in the presence of several metal ions were analysed in MeCN/H2O (1 : 4 v/v) solutions. A selective chelation enhancement of fluorescence (CHEF) effect was observed in the presence of Zn(2+)in the case ofL1, and in the presence of Cd(2+)in the case ofL2, following the formation of a 1 : 1 and a 1 : 2 metal/ligand complex, respectively, which was also confirmed by potentiometric measurements.H-1 and(13)C NMR measurements in CD3CN/CDCl(3)in combination with molecular mechanics calculations show that for both complexes ofL1andL2with Zn(2+)and Cd2+, respectively, the coordination of the carbonyl group from the pendant arm could be the origin of the observed optical selectivity.