- The Anion-Naphthalenediimide Interaction: from Non-Catenated and Complex Metal-Organic Frameworks to Heterodiptopic Receptors.
Hubley, Christian Thaddeus Nam Hoon, Saha, Sourav, Strouse, Geoffrey F., Landing, William M., Zhu, Lei, Miller, Brian G., Florida State University, College of Arts and Sciences,...
Show moreHubley, Christian Thaddeus Nam Hoon, Saha, Sourav, Strouse, Geoffrey F., Landing, William M., Zhu, Lei, Miller, Brian G., Florida State University, College of Arts and Sciences, Department of Chemistry and Biochemistry
Non-covalent molecular interactions are a ubiquitous part of molecular interaction and the driving force behind macromolecules and host-guest binding. However, a more recent non-covalent molecular interaction, the cation-π interaction, has been recognized as another fundamental force behind macromolecules and host-guest binding. Along with this cation-π interaction, anion-π interactions have been demonstrated with an electron deficient aromatic ring and various anions. Naphthalenediimide (NDI...
Show moreNon-covalent molecular interactions are a ubiquitous part of molecular interaction and the driving force behind macromolecules and host-guest binding. However, a more recent non-covalent molecular interaction, the cation-π interaction, has been recognized as another fundamental force behind macromolecules and host-guest binding. Along with this cation-π interaction, anion-π interactions have been demonstrated with an electron deficient aromatic ring and various anions. Naphthalenediimide (NDI) represent a unique class of molecules that exhibit electron deficient aromatic rings suitable for anion-π interactions. Although the anion-pi interaction has been available for some time, there has been little known about the mechanism by which this interaction occurs. Recently published anion-pi interactions, through the anion-naphthalenediimide interactions, have given insight to the mechanism by which the phenomena occurs. With this recent insight, this research attempts to apply this knowledge to two areas of chemistry, metal-organic frameworks and ion-pair recognition chemistry. A metal-organic framework (MOF) is a material defined by its crystallinity and is composed of a metal ion, or metal clusters, connected to a rigid organic molecule, known as the organic linker or ligand. MOFs have gathered significant attention in the recent decade due to their unique properties such as extremely high surface area, ultra-low density, and others. One of the primary uses for MOFs is for gas storage and capture. Despite the many advancements of MOFs, their synthesis still poses challenges. One such challenge is catenation (interpenetration), which is the formation of subunits of MOFs within themselves. This catenation reduces the available space within a MOF. Several ways to prevent catenation have been demonstrated by using bulky ligands or templating agents. Inspired by this work, this research demonstrates how the anion-π, using perchlorate anion and NDI, can be used to direct the assembly of a two dimensional MOF without catenation. In addition, coordination complexes are prepared and give additional insight to the effects of solvents on coordination of ligands to metal. At the same time, more insight is gained from these coordination complexes and the interaction between the complex and anion. After displaying how the anion-NDI interaction can be applied to prevent the catenation of MOFs, this research investigates complex NDI ligands for the assembly of complex MOFs. MOFs have expanded into many other areas of chemistry and are no longer thought about for simple gas storage. Drug delivery, catalyst, sensors, and many other areas of chemistry are beginning to utilize MOFs. However, if these areas are to successfully apply MOFs, a simple MOF with little or no complex functionality will not work. Therefore, MOFs displaying complex functionality are needed. With complex MOFs in mind, this research set out to build MOFs displaying complex functionality, for sensing, redox potential, and other applications yet to be discovered. To impart complex functionality upon a MOF, one can use a complex ligand, metal ion, or insert materials into the MOFs. Here, research focus is on the synthesis of complex NDI ligands, by adding functionality to the core of the NDI, which then imparts complex functionality on the MOF or can help with retention of ions so that the MOF can possess functionality, such as a redox potential. This part of the research began with the synthesis bromine core-substitution of NDIs that allow for post-synthetic modification (PSM) of bromo-core-substituted MOFs with a variety of nucleophiles, thereby allowing access to a large variety of complex NDI based MOFs. This work is followed by the synthesis of the complex NDI ligand by functionalizing the core of the NDI with ethoxy functionality. Although the NDI is identified as viable candidate for the assembly of complex MOFs, another building block, tetrathiafulvalene (TTF), is also identified. TTF is a unique molecule with exceptional redox ability and is often employed as a building block in many supramolecular systems. In the attempt to address complex MOFs, the synthesis of ligands containing the TTF core is demonstrated and future work will allow for assembly of TTF ligand containing MOFs. Lastly, this research shifts direction back to the anion-NDI interaction in an attempt to apply the interaction to the area of chemistry known as ion-pair recognition. Due to the ubiquitous nature of ionic species in chemistry, biochemistry processes, and in the environment, capturing these ions has gained much attention from the chemistry community. Traditional means of capturing these ionic species involves capturing either the cation or the anion. However, a more recent strategy has been to capture both ionic species at once, using a heteroditopic receptor. The traditional heteroditopic receptor relies on well-known non-covalent interactions for capture. This research attempts to introduce the anion-π interaction, using naphthalenediimide, for the cooperative binding of both ionic species, in which the anion is captured through the anion-π interaction. In addition to cooperative binding using the anion-π interaction, recycling of the receptor is another aspect of this research, which is often an aspect ignored by the field due to the high energy barrier required to overcome. Currently, this research presents successful synthesis of heteroditopic receptors with indication of cooperative binding of both ionic species using the anion-π interaction. Future studies of these receptors will be done to determine their releasability.
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