Selective optical sensing of iron(III) ions in an aqueous medium by benzochromone-based Schiff base and its application on test strips

ABSTRACT

In this work, we designed and synthesized a novel, simple, low-cost, and effective chromone–based Schiff base ligand (HL) and its application as a chemosensor for Fe³⁺ detection. The structure of the synthesized sensor bears carboxylic, azomethine, and carbonyl groups which act as chelating sites for the detection of Fe³⁺ ions. The chemosensor HL exhibited highly selective detection of Fe³⁺ via a significant colour change from yellow to brown. The colour change is due to the ligand-to-metal charge-transfer (LMCT) mechanism. The sensor (HL) was characterized using UV-Vis, FTIR, NMR (¹H- and ¹³C), and mass spectroscopy. The ligand solubility, detection condition, and sensitivity assessment suggested optimal use of DMF-water (9:1 v/v) as a working solvent at pH 7.0. Among a list of 15 metal ions screened, HL was highly selective, with instant response, towards Fe³⁺ ions without significant interferences with the other metal ions. The complexation ratio and association constants of HL to Fe³⁺ was determined by Job’s plot and Benesi–Hildebrand methods, and were 2:1 and 2.24 × 10³ M⁻¹, respectively, with a detection limit of 2.86 μM. The HL probe was also applied to detect Fe³⁺ in real samples with acceptable performance. The simple test strips have been successfully developed and applied to the visual monitoring of Fe³⁺ ions with a detection limit of 68 µM. The DFT was used to examine the best interaction mode of HL with Fe metal to be Fe(III)–L or Fe(III)–2L. The chemical-reactivity and molecular electrostatic optional were figured to predict the interaction behaviour of the tested compounds.

GRAPHICAL ABSTRACT

KEYWORDS:

• Chemosensor
• Schiff base
• colorimetric detection
• iron ion
• detection limit

Acknowledgements

We gratefully acknowledge Al-Baha University for the required facilities.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability statement

The data that support the findings of this study are available from the corresponding author, [Ali Q. Alorabi], upon reasonable request.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.