Synthesis, characterization, and fluorescence behavior of four novel macrocyclic emissive ligands containing a flexible 8-hydroxyquinoline unit

Four emissive macrocyclic ligands mono-substituted with an 8-hydroxyquinoline pendant arm are presented. The new compounds have been used for metal-ion detection, which results from the competition between PET (photo-induced electron transfer) and PPT (photo-induced proton transfer) mechanisms. Solid metal complexes with divalent Cu(II), Zn(II), and Cd(II), and trivalent metal ions Al(III) and Cr(III) have been also synthesized and characterized. The compounds have been isolated as mononuclear or dinuclear (Cu(II)) complexes, confirming the stoichiometry observed in solution.