Determination of the surface acidity of a free-base corrole in a self-assembled monolayer

Abstract

Mixed self-assembled monolayers (SAMs) containing a corrole moiety have been prepared to examine their electrochemical properties and surface acidity, with the eventual goal of biosensor development. Mixed SAMs consisting of 6-mercapto-hexanol (6-MHO) and 8-amino-1-octanethiol (8-AOT) in varying ratios were modified with a free-base corrole and characterized via Osteryoung square-wave voltammetry and contact angle measurements. The surface acidity of the free-base corrole was determined using an electrochemical titration method, with pK(a) values established at 6.4 when using Fe(CN)(6)(4-)/Fe(CN)(6)(3-) as a redox probe and at 6.7 when using iodide, and assigned to the CorH(4)(+) reversible arrow CorH(3) + H(+) equilibrium.