The Differential Impact of Resorcinarenes on Ferrocene Redox Couple: Towards Electroactive Host-Guest Systems

Abstract

Alternative to complex labelling of resorcinarene hosts with redox-active probes, non-covalent complex formation offers a unique avenue towards the design of dynamic electro-active host-guest systems towards application in sensors and functional materials. Here, resorcinarene hosts were evaluated with a well-known redox probe, ferrocene (Fc). Specifically, hosts were designed based on tuning the resorcinarene rim with functional groups to allow for hydrogen bonding, pi-pi stacking, hydrophobic and electrostatic interactions. Cyclic voltammetry was used with glassy carbon electrode as a working electrode in organic solvent to evaluate interactions between hosts and Fc. Specifically, the electrochemical properties of Fc, hosts, and host-Fc mixtures were evaluated with respect to the ferrocene/ferrocenium redox couple (reversibility, current and potential). Depending on the host structure, all hosts induced a potential shift of ferrocene/ferrocenium redox couple. The reversibility of the redox couple was maintained with certain hosts, while others resulted in surface fouling. The electrochemical studies were further supplemented by non-electrochemical methods, such as nuclear magnetic resonance, spectroscopy, mass spectrometry as well as theoretical calculations using density functional theory. Data show that controlled and tunable redox host-guest systems with well-defined redox properties may be achieved through chemical modifications of hosts, which may be used to inform functional sensors and devices with a wide range of applications such as phosphate analogue detection.