Electrooptical characteristics and anion binding behaviour of organic receptors: Effect of substitution on colorimetric response

Abstract

A series of four organic receptors, R1, R2, R3 and R4 possessing [sbnd]NH unit as binding site with varied positional substitution of [sbnd]OH and [sbnd]NO2functionalities have been synthesized and studied for their anion binding ability. Significant changes were observed in the UV vis spectra of receptors with the addition of AcO?ion justifying the observed color changes visible to naked eye. Receptors R1, R2 and R3 showed mild color changes in the presence of F?and H2PO4 ?ions whereas R4 exhibited selective response towards AcO?ion. UV vis titration and cyclic voltammetric studies performed with the incremental addition of AcO?ion to the receptors confirmed the anion binding process. The band gap value derived from the experimental results of UV vis spectroscopic and cyclic voltammetric studies support the formation of AcO?ion-receptor complex. 1H NMR titration studies performed with the addition of AcO?ion to receptor R3 confirms the deprotonation of the [sbnd]NH proton involved in the binding mechanism. 2017 Elsevier B.V.