Neutral and Charged Receptors as Voltammetric Sensors for Ions

Abstract

Electrochemical studies for all the molecules were carried out using cyclic voltammetry. Neutral anthrone derivatives- anthrone1, anthrone2 and anthrone3 were studied electrochemically for sensing cations at galssy carbon electrodes. On the basis of the results obtained mechanism of metal ligand complexation on the electrode is proposed to explain the preferential oxidation at the electrode. Anthrone derivatives showed selectivity toward copper and mercury ions even in the presence of other metal ions. Electrochemical reaction of anthrone3 was identified as a kinetically controlled process rather than a diffusion-controlled process based on different scan rates. Influence of polarity of the solvent on the shape and peak position is also studied. Electrochemical behavior of positively charged anthrone derivatives BPODS and BPMS, functionalized with viologen group were inspected extensively using cyclic voltammetry, taking clue from colorimetric studies of these molecules indicating their selectivity towards anions like cyanide, acetate and fluoride. Cation selectivity of anthrone derivative changed to anions because of the viologen group. Anthrone derivative stabilizes viologen through conjugation, reducing one of its two redox couples which are characteristics of viologen group for molecule 1. Mechanisms were proposed duly supported by density functional theory calculation based theoretical studies carried out using Guassian 03W for the electrochemical behaviour of the compounds 1 and 2. Voltammograms of dicationic viologen derivative 1 showed near quenching of anodic peaks (a decrease of almost 90% of current) as well as cathodic peaks (a decrease of almost 100% current) in presence of 1 equivalent of cyanide ions. The monocationic viologen derivative 2 also showed quenching of the cathodic peak while anodic peak survives in presence of the anions, cyanide, acetate and fluoride.