A new selective chromogenic and turn-on fluorogenic probe for copper(ii) in solution and vero cells: recognition of sulphide by [CuL]

Abstract

A new coumarin-appended thioimidazole-linked imine conjugate, viz. L has been synthesized and characterized. L has been found to recognize Cu²⁺ selectively among a wide range of biologically relevant metal ions. The chemosensing behavior of L has been demonstrated through fluorescence, absorption, visual fluorescence color changes, ESI-MS and ¹H NMR titrations. The chemosensor L showed selectivity toward Cu²⁺ by switch on fluorescence among the 18 metal ions studied with a detection limit of 1.53 μM. The complex formed between L and Cu²⁺ is found to be 1 : 1 on the basis of absorption and fluorescence titrations and was confirmed by ESI-MS. DFT and TDDFT calculations were performed in order to demonstrate the structure of L and [CuL] and the electronic properties of chemosensor L and its copper complex. This highly fluorescent [CuL] complex has been used to recognize sulphide selectively among the other allied anions. Microstructural features of L and its Cu²⁺ complex have been investigated by SEM imaging (scanning electron microscopy). The biological applications of L were evaluated in Vero cells and it was found to exhibit low cytotoxicity and good membrane permeability for the detection of Cu²⁺.