An Autocatalytic System of Photooxidation-Driven Substitution Reactions on a FeII4L6 Cage Framework

Angewandte Chemie International Edi... by Prakash P. Neelakandan, Azucena Jiménez, John D. Thoburn, Jonathan R. Nitschke  /  1d  //  keep unread  //  hide  //  preview

Article first published online: 6 OCT 2015

DOI: 10.1002/anie.201507045

http://onlinelibrary.wiley.com/doi/10.1002/anie.201507045/abstract

Abstract

The functions of life are accomplished by systems exhibiting nonlinear kinetics: autocatalysis, in particular, is integral to the signal amplification that allows for biological information processing. Novel synthetic autocatalytic systems provide a foundation for the design of artificial chemical networks capable of carrying out complex functions. Here we report a set of Fe^II₄L₆ cages containing BODIPY chromophores having tuneable photosensitizing properties. Electron-rich anilines were observed to displace electron-deficient anilines at the dynamic-covalent imine bonds of these cages. When iodoaniline residues were incorporated, heavy-atom effects led to enhanced ¹O₂ production. The incorporation of (methylthio)aniline residues into a cage allowed for the design of an autocatalytic system: oxidation of the methylthio groups into sulfoxides make them electron-deficient and allows their displacement by iodoanilines, generating a better photocatalyst and accelerating the reaction.

Sensitive operation: The incorporation of oxidizable (methylthio)aniline residues in Fe^II₄L₆ cages comprising ¹O₂-sensitizing groups and dynamic-covalent imine bonds led to a system where photooxidation became autocatalytic: transformation of methylthio groups into sulfoxides renders the aniline residues electron-deficient enough for them to be displaced by iodoanilines, generating a better photocatalyst and accelerating the reaction.