A dipodal molecular probe for naked eye detection of trivalent cations (Al 3+ , Fe 3+ and Cr 3+ ) 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 1 H-NMR, IR spectroscopy, ESI-MS spectrometry and elemental analysis. The chemosensor L can selectively detect three biologically and environmentally important trivalent metal ions (Al 3+ , Fe 3+ and Cr 3+ ) both visually and spectrophotometrically in CH 3 CN-H 2 O (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 Al 3+ , Fe 3+ and Cr 3+ ions with L, which was further confirmed by 1 H-NMR and ESI-MS studies. The binding constant values were found to be 2.9 × 10 4 M -1 for Al 3+ , 1.079 × 10 5 M -1 for Fe 3+ and 1.366 × 10 5 M -1 for Cr 3+ respectively. The detections limits of the sensor for Al 3+ (2.8 × 10 -7 M), Fe 3+ (1.9 × 10 -7 M) and Cr 3+ (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 Al 3+ , Fe 3+ , and Cr 3+ 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.