A zinc (II) complex comprising an aminoethyl‐nitropyridine‐derived N,N,O‐donor Schiff base ligand serves as an efficient ON–OFF probe for Cu(II)

Abstract

A new fluorescent zinc (II) complex‐based probe 1 encompassing a Schiff's base (E)‐2‐methoxy‐6‐((2‐[5‐nitropyridin‐2‐ylamino]ethylimino)methyl)phenol (HL) was designed, synthesized, and used for the highly selective detection of Cu2+. Ligand HL and complex 1 were characterized using various spectroscopic techniques such as 1H, 13C‐NMR, and FTIR spectroscopy, high‐resolution mass spectronomy (HRMS), UV/visible light spectroscopy, and fluorescence studies. Ligand HL did not exhibit any considerable change in fluorescence in the presence of various cations. Notably, its Zn(II) complex 1 exhibited highly selective ‘TURN‐OFF’ fluorescence signalling towards Cu2+ that remained uninterrupted with competing analytes. Probe 1 interacted with Cu2+ in 1:2 (1:Cu2+) stoichiometry as estimated through a Job's plot. Moreover, the selectivity of 1 was further confirmed through the interaction of the 1 + Cu2+ complex with some possible interfering metal ions inducing an insignificant response. Additionally, the association and quenching constant were determined to be 3.30 × 104 M−1 and 0.21 × 105 M−1 through the Benesi–Hildebrand method and Stern–Volmer plot, respectively.

A simple approach based on transmetalation for the selective and sensitive colorimetric/fluorometric detection of copper(ii) ions in drinking water

“…Therefore, overall these data suggest that 1 can potentially be employed for the quantitative detection of Cu 2+ , via colorimetric/fluorometric dual mode, by transmetalation. These results favourably compare with the few quantitative data reported in the literature for the detection of Cu 2+ by transmetalation, 27–30 with the advantage that in our case the cation salts are dissolved in water, without any pretreatment of the sample.…”

“…All measurements were recorded immediately after the addition of the aqueous solutions of the cations to MeCN solutions of 1. Identical results were obtained even recording measurements after some time(10,20,30, or 60 min later). Spectrophotometric and fluorometric titrations were performed with a 1 cm path cell.…”

“…Regarding the sensing of copper(II) ions, few examples based on transmetalation have been reported in the literature, [22][23][24][25][26][27][28][29][30] and only some of them include quantitative detection data. [27][28][29][30] Copper plays an important role in biology as an essential trace element that is fundamental to the proper functioning of enzymes, such as superoxide dismutase, cytochrome oxidase, or metallothionein. 31 Moreover, it is involved in neurobiology and in neurodegenerative disorders.…”

“…However, sensing data based on transmetalation are limited compared with the other methods. Regarding the sensing of copper( ii ) ions, few examples based on transmetalation have been reported in the literature, 22–30 and only some of them include quantitative detection data. 27–30…”

Smart and intelligent optical materials for sensing applications

“…Moreover, the overall results significantly implied that probe 1 could be used as a fluorescent chemosensor for detecting Fe 3+ for qualitative and quantitative investigations. Another work by Sharma et al [36] reported the fabrication and characterization of a new Schiff's base phenol substituent based on amino ethylnitropyridine and a zinc complex that was used for the selective detection of Cu 2+ . Pandey et al [37] used steady‐state and time‐domain methods to regulate the effects of halides on fluorescence properties in aqueous acid solutions.…”