Thiocarbazone‐appended coumarin: An easily accessible ratiometric fluorescent chemosensor for multianalyte (Zn²⁺ and Cu²⁺) systems

Abstract

A simple thiocarbazone-appended coumarin derivative 1 with high selectivity as a ratiometric fluorescence sensor towards Cu 2+ and Zn 2+ in a semi-aqueous solution was synthesised and characterised. Upon the addition of Cu 2+ and Zn 2+ , the emission of 1 solution undergoes a blue and red shift to 480 and 545 nm according to the intense blue and yellow colour under a 365-nm ultraviolet lamp, respectively. Binding was confirmed by ultraviolet-visible absorption analysis, fluorescence measurement, mass spectrometry, proton nuclear magnetic resonance, Fourier Transform-infrared spectroscopy and density functional theory calculation. The results show that 1 coordinated with Cu 2+ and Zn 2+ in different modes, resulting in different ratiometric fluorescence responses. The detection limits of the sensor 1 for Cu 2+ and Zn 2+ were 100.8 and 11.5 nM, respectively. The association constants (K a ) of Cu 2+ and Zn 2+ with 1 were determined to be 5.59 × 10 4 and 5.08 × 10 4 M −1 , respectively. Fluorescent microscopy experiments demonstrated that probe 1 has the potential to be used to monitor Zn 2+ and Cu 2+ in living cells.

Copper (II)-Catalyzed Oxidation of Ascorbic Acid: Ionic Strength Effect and Analytical Use in Aqueous Solution

“…In our opinion, it is a good result in comparison even with more complex fluorimetric techniques using sophisticated chemosensors. Although the kinetic method using ascorbic acid oxidation shows higher LOD for Cu 2+ than 20 nM [35], 4.7 nM [36], and 24.5 nM [37] and slightly higher than LOD of inductively coupled plasma-atomic emission spectroscopy (74 nM [54]), this technique is more sensitive than the reported fluorescent ones [38][39][40][41][42][43][44][45][46][47][48], atomic absorption spectroscopy (AAS) [49] (however, preconcentration methods [50][51][52] improves the sensitivity of AAS by 10 times compared to the proposed method) and atomic emission spectroscopy [54]). Another advantage of the proposed method is its probable applicability for determining the equilibrium concentration of copper (II) ions in complex systems containing ligands (including biomacromolecules such as nucleic acids and proteins), i.e., for studying the coordination equilibria and determining the stability constants of Cu 2+ complexes.…”

“…It is worth noting that other analytical methods of copper (II) determinations are known, including the classic ones (chelatometry, coulometry, etc.) and several fluorimetric sensors designed recently (see, e.g., just a few of them in papers [35][36][37][38][39][40][41][42][43][44][45][46][47][48]). However, the relatively low sensitivity and selectivity are the disadvantages of the classic techniques, and a preconcentration of copper (II) is required to achieve the nanomolar limit of detection using atomic absorption spectroscopy [49][50][51][52], while the fluorescent sensors are often difficult to synthesize.…”