A dipodal molecular probe for naked eye detection of trivalent cations (Al3+, Fe3+and Cr3+) in aqueous medium and its applications in real sample analysis and molecular logic gates

A simple and low cost multifunctional colorimetric receptor L has been designed, synthesized and characterized by ¹H-NMR, IR spectroscopy, ESI-MS spectrometry and elemental analysis. The chemosensor L can selectively detect three biologically and environmentally important trivalent metal ions (Al³⁺, Fe³⁺and Cr³⁺) both visually and spectrophotometrically in CH₃CN–H₂O (1 : 1, v/v) solution in the presence of other biologically relevant metal ions. The Job''s plot analyses indicate the 2 : 2 binding stereochemistry for Al³⁺, Fe³⁺ and Cr³⁺ ions with L, which was further confirmed by ¹H-NMR and ESI-MS studies. The binding constant values were found to be 2.9 × 10⁴ M⁻¹ for Al³⁺, 1.079 × 10⁵ M⁻¹ for Fe³⁺ and 1.366 × 10⁵ M⁻¹ for Cr³⁺ respectively. The detections limits of the sensor for Al³⁺ (2.8 × 10⁻⁷ M), Fe³⁺ (1.9 × 10⁻⁷ M) and Cr³⁺ (2.5 × 10⁻⁷ M) are far below than the limit set by the World Health Organization (WHO) for drinking water. Moreover, colorimetric test kits for rapid detection of Al³⁺, Fe³⁺, and Cr³⁺ could be successively applied for all practical purposes, indicating its potential use in environmental samples. It has also been used in building molecular logic gates.

A dipodal reversible colorimetric trivalent metal ion chemosensor (L) has been designed and synthesized. The chemosensor L successfully detects Al³⁺, Fe³⁺ and Cr³⁺ based on binding site-signaling approach and it has practical application.