Dipodal quinoline-tethered fluorescent probe synthesis and investigation of spectroscopic properties

Novel quinoline-tethered fluorescent probe was designed and synthesized as multidentate ligand. Their sensing actions were confirmed by UV–Vis absorbance and emission spectroscopic studies in presence of perchlorate salts of Co2+, Li+, Fe2+, K+, Pb2+, Cu2+, Zn2+, Ni2+, Hg2+, Ag+ cations in acetonitrile (1 × 10−5 M for absorption studies, 1 × 10−7 M for fluorescence studies). It was found that the dipodal compounds can selectively bind to Cu2+ and Ag+ metal ions with a significant quenching in their emissions. The capture of Cu2+ and Ag+ by the probe resulted in deprotonation of the secondary amine conjugated to the quinoline-tethered probe, so that the electron-donation ability of the ‘N’ atom would be greatly enhanced and the probe (2) showed blue-shift in emission and exhibited an on-off fluorescent response. The binding study was explored by using fluorescence spectroscopy with Job plot method.