Development of the weak-link approach for functional supramolecular structures

This dissertation describes the development of a synthetic methodology known as the Weak Link Approach for the synthesis of transition metal-containing supramolecular assemblies that have the ability to function as catalysts and/or sensors. In the early chapters of the thesis, studies into the generality and tailorability of this approach are described. Specifically, these studies examined the role of the three building blocks (hemilabile ligand, metal center, ancillary ligand) in this approach. To this end, a variety of metal centers were employed with simple hemilabile ligands to provide a basis of knowledge about the formation of supramolecular macrocycles and their reactivity with small molecules (Chapter 2). Specifically, metal centers with different coordination geometries, charge, and electron configurations, such as Cu(I), Ir(I), Ag(I), Ni(II), Ru(II), were utilized.;In addition to the metal centers, a number of new ligands were designed, synthesized, and characterized in which certain properties were altered (e.g., electron density, number of binding sites, etc.). The supramolecular assemblies that are formed from these ligands in combination with the appropriate metal centers have provided insight into our ability to control the small molecule reactivity of these structures. For instance, these studies demonstrate that the reactivity of the assemblies can be controlled by altering the electron density of the ligands (Chapter 3). Additionally, the ability to generate multimetallic supramolecular prisms is demonstrated through the synthesis of multiple tetrametallic complexes (Chapter 4).;In Chapter 5, a functional supramolecular system which can catalyze reactions and detect the presence of small molecules is realized. This work was made possible by the earlier studies into the generality of the WLA and the reactivity of the model assemblies. In these studies, the idea of an ELISA-like assay capable of detecting a range of analytes motivated the development of the small molecule signal amplification and detection system. The catalyst is switched "on" by an analyte behaving as an allosteric activator. In this manner, nanomolar concentrations of Cl- ions and diimine molecules were catalytically amplified and detected. The three-part detection scheme involving analyte binding, allosteric activation, and signal transduction, represents a new and general approach to small molecule detection.