Synthesis and Optimization of Diphenyl Ether-Based Receptors for the Selective Detection of Cyanide Ions in Neutral Semi-Aqueous Medium

摘要

The discharge of toxic cyanide ions in the environment and their uptake by life is inevitable due to industrialization. Therefore, its detection below the permissible limit is significant. Diphenyl ether-based chromophores have been synthesized and optimized to highlight the proton abstraction mechanism for detecting anions. Absorption studies in the presence of different solvents (H2O, MeOH, ACN, DMSO, CHCl3 and semi-aqueous ACN) and pH (10 to 4) confirmed the proton abstraction mechanism validated using H-1 NMR titration, IR studies and DFT calculations. The effect of substituents on the diphenyl ether motifs highlighted the selectivity of anions under different solvent conditions. Finally, compound-2 [2-(2-methoxyphenoxy)-5-nitrobenzoic acid] and compound-2 c [3-methoxy-4-(2-nitrophenoxy) benzoic acid] in ACN medium detected F- (280 nM, 17 mu M) AcO- (41 nM, 40 mu M) and CN- (50 nM. 1.5 mu M) ions in nM and mu M range respectively. However, the semi-aqueous medium (5 % water in ACN) gave selective detection of the CN- ion up to 100 nM for the compound-2 in a 1 : 1 stoichiometry. The use of an aqueous medium in the case of compound-2 c did not show detection for any of the ions.