Functional supramolecular architectures : mechanistic analysis of solid-state colorimetric switching and creation of novel energy conversion materials

There is still a great deal to learn about the assembly and dynamic properties of solid-state supramolecular architectures. The higher order structure of solids imposes severe limitations on molecular motion and dynamics. Yet, there is growing interest in creating dynamic solids that assemble in predictable ways for functional applications, including sensing and energy conversion. An understanding of the interplay between all of the relevant non-covalent interactions is fundamental for the rational design of such architectures. Electrostatic interactions of all types, including hydrogen bonding and van der Waals interactions, combine to determine the exact intermolecular geometries adopted by organic molecules and assemblies in solids, liquids, and mesophases. A significant portion of work in the Iverson group has broadly focused on the self-assembly of aromatic units, both in solution and more recently, in the solid-state. This dissertation builds on this body of research and describes fundamental investigations into intermolecular interactions that give rise to functional supramolecular architectures, driven by the self-assembly of organic molecules in the solid-state. The majority of this work describes the stimuli-responsive colorimetric switching of polymorphic monoalkoxynaphthalene-naphthalimide (MAN-NI) donor-acceptor dyads in the solid-state, with a primary focus on a detailed mechanistic analysis that allowed us to discover how this dramatic mechanism operates in the solid-state. Chapter 1 provides an introduction to non-covalent interactions, polymorphism, and stimuli-responsive materials. Chapter 2 describes the synthesis of 14 new MAN-NI dyads, and goes on to provide an in-depth structural and spectroscopic characterization illustrating the different polymorphs that can be formed by symmetric and asymmetric dyads, as well as the photophysical origins for the differences in color between various polymorphs. Chapter 3 details the stimuli-responsive properties of dyads, with particular focus on the thermochromic orange-to-yellow transition seen when dyads are heated. Detailed structural, spectroscopic, thermal, and morphological analyses are described in the context of characterizing the two different states. Chapter 4 goes on to describe the mechanistic analysis that uncovered the presumptive molecular switching mechanism, and the key interactions that enable polymorphic switching mechanisms. Chapter 5 details the application of aromatic interactions for the rational design of supramolecular assemblies in perylene diimides (PDI) for novel energy conversion materialsChemistr