Stimuli-Responsive Heteroligated Supramolecular Assemblies

A long-standing goal in chemistry is to mimic the properties of biological systems, such as their selectivity and their highly regulated nature, in abiotic systems in hopes of making synthetically useful catalysts that meet or even exceed the capabilities of natural systems. There are several strategies for synthesizing abiotic assemblies, and one coordination-chemistry driven method is the "weak-link approach". The weak-link approach results in stimuli-responsive supramolecular systems, and therefore is an attractive platform for synthesizing abiotic frameworks that mimic the allosteric, recognition, and amplification properties of biological systems. The halide-induced ligand rearrangement (HILR) reaction allows for the synthesis of heteroligated weak-link approach complexes, in which two different functional groups can be oriented in a parallel planar manner. The goal of this work was to first understand the mechanism behind the assembly of heteroligated weak-link approach complexes, in which two different hemilabile ligands are coordinated to one metal center. This was addressed through the research presented in Chapters 2 and 3. Specifically, the research described in Chapter 2 revealed the importance of the ligands' chelating abilities in the Pt(II) HILR reaction. This work also called attention to the lability of the phosphino-chalcoether ligands used in WLA complexes, which is a serious limitation when defined three-dimensional supramolecular systems are desired. The research discussed in Chapter 3 elucidates the mechanism of the HILR reaction. This study showed that the first intermediates in the HILR reaction are the two homoligated complexes, which then rearrange to yield the desired heteroligated complex due to the ability of the chloride to move between the inner and outer coordination spheres.;This knowledge then enabled the design of a new ligand system for the synthesis of the air- and chemically-stable complexes, as described in Chapter 4. This enhanced chemical stability relative to entirely phosphine-based WLA complexes potentially will allow for the development of a wide variety of novel catalytic systems. Finally, new types of stimuli-responsive systems accessible via the WLA were explored in Chapter 5. The research described in this Chapter reveals successful strategies for obtaining crystalline and amorphous porous materials that incorporate WLA complexes as a morphology switch.