LAUSR

Abstract Two new macrocyclic ligands Ln (L and L′) bearing two fluorophore naphthalene moieties were synthesized and characterized by employing 1H and 13C NMR, IR, microanalysis as well as mass spectrometry. Comparative studies on the effect of assorted metal cations as Cr(III), Cu(II), Zn(II), Cd(II), Pb(II), Na(I), Ni(II), Co(II), Ba(II), Fe(II), Al(III), Mg(II), Cs(I), Ca(II), Hg(II), K(I), Mn(II), Ag(I), Fe(III) on fluorescence and UV–vis spectra of Ln in ethanol illustrated that both of the macrocycles were sensitive and selective fluorescence chemosensors for Al(III). Remarkable binding constant values as 1.36 × 105 M−1 and 1.15 × 105 M−1 alongside 1:1 stoichiometry for Al(III)/L and Al(III)/L′ were established by employing fluorescence spectrophotometry. Monitoring of probable coordination sites on Ln to Al(III) by 1H NMR spectroscopy indicated on the coordination of both N- and O-donor groups in DMSO-d6. In order to elucidate the effect of macrocyclic nature in this O2Nx naphtha-aza-crown family on the observed fluorescence chemosensing behavior of metal ion, two new O2Nx-donor macroacyclic ligands were also prepared and characterized by the abovementioned methods. The comparative experiments revealed that the macrocyclization had an escalating role on the fluorescence parameter of the macrocycle as a metal-ion chemosensor.