Synthesis of novel building blocks for the formation of redox-responsive supramolecular organic frameworks

Abstract

In recent decades, porous reticular materials such as metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) have attracted significant interest for applications ranging from storage and separation to catalysis. However, these crystalline materials exhibit their porosity in the solid state and are often insoluble or unstable in solution, which restricts their effective utilization in homogeneous media. One strategy to overcome these limitations is to exploit the solution self-assembly of suitable molecular building units via noncovalent interactions to construct soluble porous network structures, also referred to as supramolecular-organic frameworks (SOFs). SOFs can retain their periodicity and porosity in solution, which may lead to promising applications in homogeneous catalysis, drug delivery, and energy conversion. Artificial self-assembled materials typically exist in thermodynamic equilibrium states, and their formation is governed by thermodynamic stability. In contrast, biological self-assembled structures, such as microtubules, operate in non-equilibrium states, with their formation controlled by fuel-driven dissipative self-assembly (DSA) via a constant exchange of energy and matter with the environment. The implementation of DSA in artificial materials is currently a very active research topic in supramolecular chemistry. The overall goal of this TFG project is to synthesize a novel porous supramolecular network formed from two different π-conjugated dye molecules in water. The formation of this system relies on β-CD/ferrocene (Fc) host-guest interactions between a Fc-functionalised Zn-porphyrin and a perylene diimide derivative grafted to two β-CD moieties, with the latter acting as a ditopic host linker. Due to the redox-responsive nature of the β-CD/Fc interactions, dissipative self-assembly can eventually be implemented in this system, where the disassembly/assembly of the network can be activated/deactivated by modulating the supply of redox chemical fuels. To this aim, we first prepared and characterized both building blocks of the SOF through convergent multistep synthesis. Then, we performed spectroscopic characterization and studied their self-assembly behaviour individually in water using UV-Vis, fluorescence and DLS measurements. Finally, we conducted preliminary studies to investigate how the sample preparation protocol affects their self-assembly behaviour.