Viologen substituted anthrone derivatives for selective detection of cyanide ions using voltammetry

Electrochemical behavior of anthrone derivatives 1 (1-(2,7-dioxo-3,7-dihydro-2H-naphtho[1,2,3 de]quinolin-1-yl)-1'-heptyl-4,4'-bipyridine-1,1'-diium) and 2 (1-(2,7-dioxo-3,7-dihydro-2H-naphtho[1,2,3-de]quinolin-1-yl)-[4,4'-bipyridine]-1-ium functionalized with viologen group are inspected extensively using cyclic voltammetry. Colorimetric studies indicate their selectivity towards anions like cyanide, acetate and fluoride. Cation selectivity of anthrone derivative changes to anions because of the viologen group. Anthrone derivative stabilizes viologen through conjugation, reducing one of its two redox couples which are characteristic of viologen group for molecule 1. Mechanisms are proposed and supported by theoretical studies carried out using Guassian 03W for the electrochemical behaviour of compounds 1 and 2. Voltammograms of dicationic viologen derivative 1 show near quenching of anodic peaks (a decrease of almost 90% of current) as well as cathodic peaks (a decrease of almost 100% current) in the presence of 1 equivalent of cyanide ions. The molecule 2 undergoes quenching of the cathodic peak while anodic peak survives in the presence of the anions, cyanide, acetate and fluoride. The proposed electrochemical sensors are selective for CN-, OAc- and F- based on binding constants which are much larger than for anions like Cl-, Br-, I-, HSO4-. The proposed voltammetric method for the cyanide determination is compared with potentiometric and spectrophotometric methods for cyanide determination. The proposed voltammetric method has also been used for quantitative determination of cyanide in unknown samples.