Water compatible small organic molecular probes for dual and individual detection of metal ions

Abstract

Essential metals such as Na+, K+, Mg2+, Cu2+, Ni2+, Fe2+, Zn2+etc. play important roles in living systems at a specific concentration. The imbalance of essential metal ions and the presence of non-essential metal ions, such as Cd2+, Pb2+, Hg2+, and Au3+etc. cause serious health issues due to their toxic effects. The widespread applications of metals in several fields, such as chemistry, modern industry, agriculture, and biomedicine, are responsible for environmental pollution. In this connection, detecting metal ions has received much attention in the research community. We discussed the detection processes of Cu2+, Ni2+, Fe2+, and Au3+ions by water-soluble simple fluorometric sensors 1-7 in the thesis. The triazole-appended quinoline fluorescent sensor 1 exhibited dual fluorometric selectivity for Cu2+ and Ni2+ions in MeOH/H2O (7/3, v/v). The naphthyl-based fluorescent compound 2 was used to establish the binding mode of the sensor. In the aqueous medium, we proposed that sensor 1 form a tridentate coordination complex with Cu2+ and Ni2+ions via the quinoline N atom, NH group, and triazole moiety. newlineAs a continuation, the reversible fluorescence sensor 3 has been reported for the discrimination of metal ions in an aqueous medium after excitation at a higher wavelength. Sensor 3 showed specific sensing properties towards Cu2+ and Ni2+ in aqueous solutions of DMSO and CH3CN. The discrimination of Cu2+and Ni2+ions was carried out by controlling the testing medium. Model compound 4 was used to determine the binding mechanism of sensor 3 with Cu2+and Ni2+ions. Finally, DFT calculations were performed to establish the binding mode of 3 with Cu2+and Ni2+through the triazole N atom, -NH group, and the quinoline N atom. newlineThe sensing properties of naphthaldimine-glucofuranose conjugates 5 and 6 towards metal ions were investigated by 1H NMR titration, UV-vis, and fluorescence spectroscopic methods. Studies of absorbance and fluorescence showed that compound 5 coordinated with Fe2+and Cu2+ions in DMSO by changing colour from