A simple sulfonohydrazide Schiff base molecular probe for colorimetrically selective recognition of Cu2+ ion in Semi-Aqueous medium.

[Display omitted] • A simple and novel Schiff base that is selective for cupric ions. • NMR, FTIR, and ESI-MS spectroscopy methods were used to confirm the interaction of the probe with the analytes. • Probe R1 effective sense at colorimetric method was observed to be 2.74 × 10-7 M detection limits. • The analysis kit was created to track the use of cupric ions in real-time. A novel sulfonohydrazide Schiff base colorimetric probe 4-methylbenzenesulfonohydrazide (R1) has been designed and synthesized which shows sensing recognition of Cu2+ in CH 3 CN:H 2 O (7:3, v/v) semi-aqueous medium. The prepared probe R1 was characterized using spectroscopic methods, including FT-IR, 1H NMR, and HRMS spectrometry. R1 exhibits an excellent selectivity to Cu2+ over other examined metal ions with a prominent colorimetric performance from colorless (345 nm) to crimson yellow (420 nm) under daylight. UV–vis titration experiment in the presence of different molar fractions of Cu2+ was used to perform a Job's plot analysis. The results showed that the stoichiometric ratio of the complex formed by R1 and Cu2+ was 2:1. A paper strip pre-stained with R1 solution was further fabricated and it also showed excellent sensing ability toward Cu2+ with a detection limit as low as 2.74 × 10-7 M with the naked eye, which represents better portability and operation simplicity that is favourable for on-site analysis of Cu2+ in water. The sensing mechanism was further verified with HOMO–LUMO energy levels were calculated using experimental and theoretical studies (DFT/TD-DFT), which correlated with good agreement. [ABSTRACT FROM AUTHOR]