title: Multi-signaling thiocarbohydrazide based colorimetric sensors for the selective recognition of heavy metal ions in an aqueous medium.
abstract: A series of colorimetric chemosensors R1-R6 have been developed from thiocarbohydrazide derivatives, for the selective detection of heavy metal ions. The structures of the receptors R1-R6 were well characterized by standard spectroscopic techniques like FT-IR,1H NMR, and ESI-MS. The solid structure of receptor R1 and R2 were derived by single crystal X-ray diffraction (SC-XRD). The cation reorganization abilities of receptors R1-R6 were studied by UV-Vis spectroscopy. The receptors R1, R3 and R4 acts as a tremendous sensitive probe for heavy metal ions (Hg2+, Cd2+and Pb2+) with the μM detection (R1 for Hg2+, 2.72, R3 for Cd2+, 3.22, R4 for Hg2+, Cd2+& Pb2+, 0.70, 0.20 & 0.30μM) and the receptors R2, R5 &R6 are sensitive towards Cu2+ions with the μM detection (3.34, 0.90 & 1.20μM) in an aqueous medium among all other tested cations. The receptor R4 shows a multi-color response towards Hg2+, Cu2+, Cd2+and Pb2+ions. The recognition mechanism, stoichiometric binding ratio and detection limit (DL) have been examined by UV-Visible spectroscopic titration experiments and Benesi-Hildebrand (B-H) plot, receptor R1-R6 sowed 1:1 binding ratio with good binding constant range of 103to 105M-1with Hg2+, Cu2+, Cd2+and Pb2+ions metal ions.
authors.affiliation: Supramolecular Chemistry Laboratory, Department of Chemistry, National Institute of Technology Karnataka (NITK)-Surathkal, Mangalore 575 025, India.
authors.forename: Bharath Kumar
authors.initials: BK
authors.lastname: Momidi
authors.affiliation: Supramolecular Chemistry Laboratory, Department of Chemistry, National Institute of Technology Karnataka (NITK)-Surathkal, Mangalore 575 025, India.
authors.forename: Venkatadri
authors.initials: V
authors.lastname: Tekuri
authors.affiliation: Supramolecular Chemistry Laboratory, Department of Chemistry, National Institute of Technology Karnataka (NITK)-Surathkal, Mangalore 575 025, India. Electronic address: darshak_rtrivedi@yahoo.co.in.
authors.forename: Darshak R
authors.initials: DR
authors.lastname: Trivedi
keywords: Colorimetric sensors; Heavy metal ions; Thiocarbohydrazide; UV–Vis titration