4-oxocyclohexadienylidene porphyrinogen as an electrochemical anion receptor

Abstract

Sensitive and selective detection of biologically and environmentally important anions has been a vast growing field in supramolecular chemistry [1,2]. Much research has been devoted to designing sensors that can selectively recognize anions. Recently, we have reported an anionic and solvatochromatic sensor [5]. (Scheme 1) In this investigation, the effect of various anions on the redox states of the porphyrinogen and its N-substituted analogues were studied. Cyclic voltammetry (CV) was employed to probe the changes in the redox potentials of the receptors upon complexation with anions. Upon addition of F- to porphyrinogen, a cathodic shift of ~520 mV corresponding to 1.F-complex was observed. The F- ion had the greatest effect on the porphyrinogen redox potentials while other anions gave modest shifts. DFT computational studies on the anion binding correlated well with the electrochemical results.