Synthesis and Design of Small Molecule-Based Functional Materials: Applications in Lithium-Ion Batteries and Molecular Machines PDF Download

Author: Geeta Vadehra
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Languages : en
Pages : 162

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Book Description
Solid-state organic chemistry is a broad topic with a wide variety of materials applications. This dissertation focuses on two very different applications, and should be considered in two separate parts. Part One focuses on the use of organic compounds as electrode materials in lithium ion batteries (Chapters Two and Three) and Part Two focuses on the design of molecular rotors for their applications in molecular machines (Chapters Four and Five). Part One. The application of organic redox reactions in lithium ion batteries is a relatively unexplored topic. Though first examined in the early 1970s, the field was quickly abandoned in favor of inorganic insertion compounds, which showed more desirable redox potentials and lower solubility in typical organic electrolyte solvents. As such, these metal oxides have dominated the field ever since. However, while these compounds show impressive performance, they are plagued with unavoidable environmental consequences of their continued use. Organic alternatives provide a useful platform to circumventing this, which has sparked a resurgence of interest in the last decade in addressing the two issues mentioned above. Chapter Two. The redox potentials demonstrated in organic redox reactions most often fall approximately halfway between those displayed by traditional cathode and anode materials--meaning that applying these to either would cut the cell voltage in half. However, as this is an effect of the electronics of the process, it follows that controlling the electronics would control this. Naphthalene diimides provide an ideal model to explore the effects of probing the electronics of the material based on their low solubility and redox capabilities. In this chapter, the synthesis and characterization of a family of naphthalene diimide derivatives is documented, along with the tunability of the electronics of the redox process based on substituent effects and the subsequent control that can be exhibited on the experimental discharge potentials. Chapter Three. The motivation for exploring the redox capabilities of organic compounds for electrodes to replace the inorganic insertion compounds that currently dominate the field is largely based on the environmental implications of the current materials. A recent discovery that a furan backbone can be accessed in highly sustainable methods provided an environmentally friendly synthesis of furan dicarbonyl derivatives such that their electrochemical activity could be characterized. Part Two. Analogous to their macroscopic counterparts, a machine on the molecular scale requires the cooperative movement of its parts. The Garcia-Garibay group has developed the design of the molecular gyroscope, which, like a macroscopic gyroscope, has both stationary and rotating parts. However, incorporation of this motion into the solid requires control not just with regard to molecular design, but, also with regard to crystal packing. In the context of the molecular gyroscope, this means that in order for the rotating component to rotate, sufficient free volume around it is required. Chapter Four. While the inability to predict crystal packing remains a major obstacle in the field of crystal engineering, it has been shown that the use of hexamethyl triptycene as the stator portion can allow for an optimal packing arrangement of the rotor molecules. However, closer inspection of the crystal structure revealed that the free volume discussed above, was actually filled by crystallographically defined solvent molecules. Despite this, the system demonstrated impressive rotational dynamics. Given the dynamics of this system in combination with analysis of the crystal structure demonstrated the presence of a correlated motion analogous to a macroscopic "gearing" system. This chapter documents synthetic advances that allow access to this system efficiently such that appreciable quantities of this rotor and a variety of its derivatives can be accessed in order to fully characterize their rotation dynamics. Preliminary data showing qualitative evidence of a correlated motion are presented, but studies are still ongoing. Chapter Five. Inspired by the work discussed in the previous chapter, it followed that while iptycene based stators would often lead to rotors with a tendency to interdigitate, peripheral substitution was a promising strategy to overcome this obstacle. Despite this, traditional strategies of synthesizing these compounds were considerably too long and low yielding to be practical for further study. With this in mind, this chapter documents the development of an efficient, high yielding method for late stage installation of peripheral substitution that can be applied not just to triptycenes, but also to pentiptycenes.