Synthesis and catalytic studies of copper(I) complexes coordinated by catenane and rotaxane ligands

Abstract

Catenanes and rotaxanes are representative classes of mechanically interlocked molecules (MIMs) consisting of physically entangled components. The interlocked components held by mechanical bonds can undergo co-conformational motions with respect to each other, which are characteristic to MIMs and resulting in their unique chemistry. Application of MIMs as coordination ligands for metal-based catalysis has gained interest in rotaxanes but remained very limited for catenanes. The interlocked ligands offer a way to modify the metal coordination properties, enabling new potentials in catalysis with different reactivity and selectivity. In this thesis, our research is focused on developing new Cu(I)-based MIMs, including their post-synthetic modifications to modify physical and chemical properties and investigating catalytic activity in carbon–carbon bond formation reactions. Chapter 1 introduces the role of metal coordination in catenane and rotaxane chemistry. Transition metal-template and active template strategies for catenane and rotaxane synthesis, effects of interlocked ligands on the transition metal coordination and applications of MIMs in catalysis are highlighted. Chapter 2 describes a post-modification of Cu(I)-based [2]catenanes. The secondary amines on the catenanes were converted to cationic ammoniums by nucleophilic substitution reactions, which improved the overall aqueous solubility and overall stability. The post-functionalized [2]catenanes were studied as catalysts for the cross-dehydrogenative coupling (CDC) reactions between N-phenyl tetrahydroisoquinolines and indoles in water using hydrogen peroxide as the oxidant. Chapter 3 describes the design, synthesis and characterization of a series of three-coordinated Cu(I)-[2]rotaxanes with various cyclic sizes, obtained by the active template approach involving the copper-mediated azide-alkyne cycloaddition (CuAAC). Tightness of the Cu(I) coordination sphere was controlled by the use of different phenanthroline-derived macrocycle sizes. The coordinatively unsaturated Cu(I)-[2]rotaxanes were investigated as catalysts for CDC reactions using oxygen as the oxidant. Chapter 4 describes the unexpected synthesis of a [3]rotaxane containing one macrocycle and two axle components using AT-CuAAC. The large macrocycle allowed double threading of the axles that resulted in the formation of a [3]rotaxane. Reaction temperature, amount of stopper groups and copper template etc., were investigated to determine the distribution of the [2]- and [3]rotaxane products. Chapter 5 is the conclusion of this thesis. Chapter 6 provides supplementary materials including experimental procedures and data.