Quinoline Containing Calixarene Fluoroionophores: a Combined NMR, Photophysics and Modeling Study

The 8-alkoxy-5-chloroquinoline fluorophore was appended at the lower rim of a calix[4]arene triamide with two different orientations. In ligand 1 the quinoline part is linked to the calixarene skeleton through the pyridine C-2 atom, while in 2 it is linked through the phenolic oxygen atom of the chromophore. The binding properties of both ligands, investigated in chloroform and methanol solutions, indicate that they are efficient fluoroionophores, with selectivity for sodium and strontium ions among alkali and alkaline earth metal ions. Combined NMR, photophysical, and modeling studies disclosed the peculiar conformational and coordination features of monovalent and divalent metal ion complexes. Lanthanide metal ion complexes were prepared and studied in acetonitrile solution showing good luminescence in the case of Nd3+, Yb3+, and Er3+ ions.