Selective detection of Cu2+ and Co2+ in aqueous media: Asymmetric chemosensors, crystal structure and spectroscopic studies

Two new azo-azomethine receptors, H2L1 and H2L2, containing hydrazine, naphthalene and different electron withdrawing groups, Cl and NO2, have been designed and synthesized for qualitative and quantitative detection of Cu2+ and Co2+ in aqueous media. The crystal structure of H2L1 is reported. The H2L1 was used as a chemosensor for selective detection of trace amount of Cu2+ in aqueous media. H2L2 was also applied to naked-eye distinction of Cu2+ and Co2+ from other transition metal ions in aqueous media. Detection limit of Cu2+ is 1.13 mu M and 1.26 mu M, in water, for H2L1 and H2L2, respectively, which are lower than the World Health Organization (WHO) recommended level. The binuclear Cu2+ and Co2+ complexes of the receptors have been also prepared and characterized using spectroscopic methods and MALDI-TOF mass analysis. Furthermore, the binding stoichiometry between the receptors upon the addition Cu2+ and Co2+ has been investigated using Job's plot. Moreover, the fluorescence emission spectra of the receptors and their metal complexes are also reported. (C) 2017 Elsevier B.V. All rights reserved.