Synthesis of electron-deficient conjugated nanorings by host-guest templates – stargate

The aim of this project is to provide access to electron-deficient conjugated nanorings (i. e. macrocycles of diameters ? 2 nm) and explore their physico-chemical properties. Large electron-rich conjugated nanorings (i. e. based on carbazole, phenylene or porphyrin) are singular structures possessing exceptional properties such as unusual fluorescence, quantum coherence, or large ring anti-aromaticity. These unique properties are of great interest for molecular electronics, or smart fluorescent compounds. However, cationic, conjugated, electron-poor nanorings have been overlooked. In fact, such compounds have to date never been described. The integration of electron-deficient structures in conjugated nanorings is expected to afford a new class of compounds with unprecedented properties. In this context, viologen building-blocks (i. e. containing 4,4’-bipyridiniums units) seem perfectly suited due to their electron-deficient nature and structural tunability. However, organizing viologens into nanorings is not trivial. In this project, we propose a straightforward strategy to access water-soluble electron-poor nanorings by using an original host-guest template approach featuring viologens, cucurbituril macrocycles and star-shape oligomers that represent an access gate to electron-deficient nanorings. We plan to investigate in detail the physico-chemical properties of this new class of compounds characterized by (i) their cationic nature, (ii) their interlocked structure and (iii) their water-solubility.