Janus fluorocyclohexanes as facially polarised motifs for organized supramolecular materials

Abstract

A Janus-face cyclohexane has a single fluorine on each carbon and with all syn configuration, creating a face of fluorines on one side of the ring and hydrogens on the other. This thesis prepares and explores the properties of derivatives of this class of molecule. Chapter 1 introduces organofluorine chemistry, its applications, and an overview of the evolution of Janus fluorocyclohexanes, detailing their initial synthesis and highlighting their unique polar properties. Chapter 2 describes the synthesis of mono-, di-, and tri-alkylated Janus fluorocyclohexane derivatives. In particular the influence of peripheral substituents on supramolecular packing was explored. The tri-alkylated systems adopted columnar discotic stacking. This research suggests that the 2,4,6 tri-alkylated ring systems have potential as a motif for ordered supramolecular assemblies and as they exhibit multiple polymorphs, they offer potential as liquid crystalline materials. Chapter 3 focuses on the synthesis of two novel Janus Organic Framework (JOF) struts, featuring carboxylic acid linkers with either tri- or penta- fluorinated Janus rings. Single crystal X-ray analysis confirmed their structure, and preliminary findings demonstrated increased porosity in first-generation JOF-MOFs compared to isolated JOF struts. Second-generation JOF-MOFs were developed through exchange synthesis with MOF-808, confirming this new class of framework, with initial results showing potential for further porosity enhancements and applications in supramolecular porous materials. Chapter 4 discusses the development of Janus cyclohexanes with a 3,6-dialkyl ether linkage, investigated for their dielectric anisotropic properties and potential use in memory storage devices. These compounds, which possess a long-chain phosphonic acid group for self-assembly on a TiN substrate were designed as potential memory storage molecules. Chapter 5 explores nucleophilic aromatic substitution reactions of pentafluoro aryl ethers, focusing on the para selectivity of these reactions and leading to the generation of Janus 3,6-di alkyl ethers, compounds which displayed significant polymorphism, suggesting potential for liquid crystal applications. In overview this body of work demonstrates new approaches to the synthesis of Janus fluorocyclohexanes and highlights possibilities for their potential applications in supramolecular assembly, liquid crystals, and organic materials science more generally.