Electrochemical behavior and redox-dependent disassembly of gallic acid/FeIII metal-phenolic networks

Upon its recent introduction, a versatile class of organic-inorganic hybrid systems known as metal-phenolic networks (MPNs) has been steadily growing its potential for applications in various fields such as catalysis, bio-imaging, and drug-delivery. Many of these applications involve the processes of mediation, disassembly, and/or release, which often rely on redox-dependent interactions. Self-assembled MPNs, possessing metal-coordinated structures, may potentially serve as redox responsive platforms, offering an additional tool of control for triggered disassembly or drug release. Therefore, a comprehensive study of MPN’s reduction/oxidation behaviour for evaluation of its redox responsiveness, specific conditions for disassembly and comments on the kinetics of metal ion release is necessary. Starting with a gallic acid – iron (GA/Fe^III) system as a simple MPN representative, we carried out electrochemical characterisation to provide valuable fundamental insights into the redox behavior of these networks. We demonstrate that GA/Fe^III is redox active, evaluate its electrochemical reversibility, identify the oxidation state of the redox active species, and provide information regarding stability towards reductive stimuli and specific redox conditions for Fe^III “on-off” or continuous release. Overall, through studying the redox properties of GA/Fe^III film, we advance the understanding of multi-functional iron containing MPNs platforms for the wide range of biologically relevant applications.