Supramolecular chemistry has become a rapidly growing field since the Nobel Prize was awarded to the work of Lehn, Pedersen, and Cram in 1987 for their pioneering work on crown ethers and non-covalent host-guest interactions. Metal-ligand interactions represent a particularly useful and well-studied means of preparing supramolecular polymers from telechelic building blocks. This present work focuses on utilizing main-chain metallo-supramolecular polymers or small molecules, based on 2,6-bis(1’-methylbenzimidazolyly)pyridine (Mebip) ligands, to create materials aimed at applications such as light healable polymers, or the detection of chemical warfare agents.
With the objective to develop new organic/inorganic hybrid materials, which combine good mechanical properties and other attractive properties with ease of processing, new classes of metallo-supramolecular polymers were explored. The general design approach merged the structure of known polymer systems, for example semiconducting polymers (poly(p-phenylene ethynylene)s) or thermally stable hydrocarbons (poly(p-xylyene)s), with the advantages of a dynamic (reversible) polymerization process, to allow access to materials that are otherwise difficult to process. The new telechelic metallo-supramolecular polymers could be readily solution-processed and represent illustrative examples for metallo-supramolecular polymers with good mechanical properties, while maintaining the properties of parent polymer.
Polymers with the ability to repair themselves after sustaining damage are poised to extend the lifetime of materials used in a wide range of applications. Reported here is the development of metallo-supramolecular polymers that can be mended through exposure to light. Upon exposure to ultraviolet light, the metal-ligand motifs are electronically excited and the absorbed energy is converted into heat, causing reversible disengagement of the metal-ligand motif and a temporary reduction in the molecular weight. As a result, defects heal quickly, with high efficiency, and if needed repeatedly.
A modular sensory system, for the detection of organophosphates, which utilizes a multi-metal/multi-ligand approach is presented. The sensing scheme relies on fluorescent sensor complexes of Mebip ligands and selected metal ions. Detection of organophosphates is accomplished through competitive coordination of the analyte with the metal. Mixing and matching consciously designed ligands and carefully selected metal ions allows the formation of sensor complexes, which allow organophosphate detection with high selectivity and sensitivity.