Binding interaction between 4-Hydroxy-3-nitrocoumarin and metal ions-A spectroscopic approach

Abstract

Metal ions play vital role in many biochemical and physiological functions when they are in very low concentrations and become lethal if certain limit is exceeded. Their detection even at very low concentration is very much essential. In this work we report the detection of metal ions Cu++ and Ni++ being members of environment pollutants using a coumarin derivative 4-Hydroxy-3-nitrocoumarin by absorption and emission spectroscopic methods. It is noticed that the metal ions are capable of reducing the absorbance (OD) and emission intensity of the coumarin derivative dissolved in Toluene, Dichloromethane and 1,2-Dichloroethane even at very low concentration of 10-3 M. The sample concentration is maintained at 10-5M. The OD is reduced with the increase in metal ion concentration without shift in absorption peak of 272 nm. Emission intensity is also quenched by them without shifting the emission peak which is located at 555 nm. The spectroscopic data is analyzed using Benisi-Hildebrand. Binding constant values are calculated using both absorption and emission data. The values are found to be towards higher side. Gibb’s free energy change which is an indication of spontaneity/non– spontaneity of compound–Metal ion binding is also evaluated. Gibb’s free energy suggests that the studied compound has more affinity towards metal ions and can selectively sense them.