New Synthetic Receptors for Molecular Recognition of Anions and Their Practical Applications

Abstract

Among the wide range of anions, the detection of fluoride ion has gained greater attention because of its privileged usage in clinical applications which made it beneficial to human health. However, the excess of fluoride consumption is health concern as it can be a cause of many lethal diseases including bone cancer. Apart from this fluoride ion detection, the detection of dicarboxylates is also a field of prominence as they play vital role in the numerous metabolic processes such as glyoxalate cycle, generation of high energy phosphate bonds etc. Considering the significance of the field, six new series of receptors based on various backbones such as 1-naphthohydrazide, benzohydrazide, aminophenol and triphenylphosphonium salts have been designed and synthesised for the colorimetric detection of fluoride ion and dicarboxylate ions and utilized for versatile applications of environmental concern. All the receptors have been characterised using different techniques such as 1H NMR, FT-IR, elemental analysis and ESI-MS. The selected receptors have been considered for three-dimensional structural elucidation using Single Crystal X-Ray diffraction (SCXRD) studies. The quantitative analysis of anions with the receptors has been carried out using UV-vis titration. The binding constant for the receptor-anion complex has been calculated using Benesi–Hildebrand equation. The binding mechanism has been proposed based on UV-vis titration and the same has been confirmed by 1H NMR titration. Based on the experimental results, it has been concluded that the simple organic molecules could act as very good colorimetric receptors for biologically important anions such as fluoride and dicarboxylate ions. Along with colorimetric detection, these receptors could show vivid analytically as well as environmentally significant applications such as quantitative analysis of fluoride ion present in sea water/mouthwash, determination of percentage composition in binary solvent mixture and extraction of fluoride ions from sea water.