From liquid crystal polymers containing crown ethers to tapered building blocks containing crown ethers which self‐assemble into tubular supermolecules

Abstract

Abstract : Molecular recognition directed self-assembly of supramolecular architectures or noncovalent synthesis, and molecular recognition directed self-assembly of transition states or self-synthesis, are two of the most active topics of research in the area of supramolecular chemistry. We are concerned with the use of the simplest endo-receptor i.e., crown ether in the design of two classes of systems. The first one is a system which is externally regulated by molecular recognition processes via a crown ether endo-receptor. This system is based on various classes of liquid-crystalline polymers which exhibit phase transitions that are manipulated by the reversible complexation of the crown ether present in different parts of their repeat unit with metal salts. The information gained from these experiments is then exploited in the design of the second group of systems. This consists of self-assembling building blocks containing various combinations of crown ether as endo-receptor and a tapered group as exo-receptor. Upon complexation with metal salts, these building blocks self-assemble into tubular supramolecular architectures. Therefore, while the first system exhibits molecular recognition directed phase transitions, the second one self-assembles into tubular supramolecular architectures via various molecular recognition processes. These tubular supramolecular architectures display a thermotropic hexagona columnar (phi h) liquid crystalline phase, which enables the structure of the self-assembled supramolecular architecture to be determined by X-ray diffraction experiments. jg