A new N-methylhydrazinecarbothioamide incorporated “naked-eye” and “turn-off” chemosensor for selective and low detection of Cu2+ ions and computation study

Abstract

The rising concentration of Cu2+ ions in the environment is dangerous and showed adverse effects on the environment and human health. To concern this issue in this work, we designed N-methylhydrazinecarbothioamidebased (E)-2-(2-methoxy-4-(3-(2-methoxy-4-((E)-(2-(methylcarbamothioyl) hydrazono)methyl)phenoxy)propoxy)benzylidene)-N-methylhydrazinecarbothioamide (PMPMMHC) new chemosensor for selective and rapid detection of Cu2+ ions with quenching in luminescence or “turn-off” response among various cations and anions in semi-aqueous medium DMSO/H2O (1/1 v/v). The addition of Cu2+ ions to the solution of PMPMMHC showed remarkable changes in color, UV–vis, fluorescence spectra, and redox potential. The insight spectroscopic titrations result in the binding stoichiometry 1:2 (PMPMMHC:Cu2+) with a limit of detection (LOD) 15 Nm showing good binding constant 1.37 × 107 L2 mol−2 as determined by the Benesi–Hildebrand Equation in the linear range of detection 20–200 μM. In computational studies, chemosensor reveals unique interaction with Cu2+ as a result of metal-pi acceptor (2.33 Å and 2.77 Å) interactions as well as the non-classical intra-hydrogen bonding. In mechanistic studies, the photoinduced electron transfer (PET) inhibits and signal changes arise due to the electronic transition of higher-energy orbitals (HOMO) to lower energy orbitals (LUMO) as a result of PMPMMHC:Cu2+ binding.