Colorimetric chemosensor based on coumarin skeleton for selective naked eye detection of cobalt (II) ion in near aqueous medium

The numbers indicating the permissible limits of concentration of the different metal ion consumptions and exposure levels on the environment are as important as their consumption for healthy existence of living systems. Overpassing these consumption and exposure limits can be unsafe for the living systems and environment. In this perspective, we developed a colorimetric probe for detection of Co2+ ion in the nearly aqueous medium which performed a color change in the solution containing cobalt from light yellow to yellowish red due to intramolecular charge transfer (ICT) upon addition of synthesized probe. The optical response and absorption spectral changes of the Co2+ ion on the coumarin-based probe were observed under different pH conditions and the neutral pH was found to be suited best which implies its applicability under physiological conditions. The probe displayed an excellent capability to detect the Co2+ ions in real samples of water collected from different sources. The analytical and stoichiometric calculations were evaluated using the Benesi-Hildebrand curve and Job's plot which revealed micromolar sensitivity and 1:1 metal-receptor binding respectively. The experimental FTIR results of ligand and its complex with cobalt were also corroborated with the Density Functional Theory (DFT) results.