Supramolecular assembly dynamics: Relationships to constituent metal -ligand complexes.

摘要

The solution dynamic behavior of metal-ligand supramolecular assemblies is examined and related to the properties of constituent coordination complexes. The structures examined are based on catecholate chelating moieties and include mononuclear ML3 complexes, dinuclear M2L 3 assemblies and cavity-containing tetranuclear M4L 6 hosts capable of encapsulating small molecules. Intramolecular isomerizations of each structure type are described and related to supramolecular architecture. In addition, host-guest exchange dynamics in M4L6 assemblies are investigated by variation of metal-ligand lability.;Chapter One defines the scope of supramolecular assembly dynamics. Kinetic and related thermodynamic studies of assembly formation, rearrangement, and host-guest encapsulation reactions are reviewed in order to create a framework in which to consider the subsequent chapters. Organic assemblies are included in the discussion Deltaof coordination assemblies in order to more completely consider relevant solution processes.;Chapter Two presents a series of M2L3 compounds designed to probe the communication of chirality from one metal center to the second through differing ligand backbones. Ligand structure not only impacts the resulting assembly structure, but also determines its accessible dynamic behaviors.;Chapter Three examines the strong mechanical coupling of metal centers in an M4L6 tetrahedron. This structural property manifests itself in the assembly's remarkable inertness to intramolecular rearrangement. The tetrahedron can be resolved into its DeltaDeltaDeltaDelta and LambdaLambdaLambdaLambda enantiomers, and the robust nature of the resolved tetrahedron has been tested in a stepwise ligand substitution experiment, which reveals the structure's unique chiral and structural memory properties.;The guest exchange dynamics of the same M4L6 host are described in Chapters Four and Five. The kinetic parameters of guest exchange in the GaIII and AlIII M4L6 assemblies are defined in Chapter Four, while Chapter Five introduces the TiIV and GeIV analogs as mechanistic probes for the reaction. Molecular modeling lends additional support for a guest exchange mechanism which does not require partial ligand dissociation, or opening of the assembly.;Finally, Chapter Six investigates the intramolecular dynamics of analogous TiIV and GeIV mononuclear complexes. These studies provide a new context in which to consider the supramolecular structures incorporating these metals. They also suggest new opportunities for predicting and controlling supramolecular dynamics. (Abstract shortened by UMI.).