NEW DESIGN CONCEPTS TOWARDS MOLECULAR BOWLS, HYPERVALENT IODINE BASED MATERIALS, AND ENERGY STORAGE MATERIALS

Author

Gajanan C. Kulkarni, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2019

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Plunkett, Kyle

Abstract

In this dissertation, new cyclopenta-fused polycyclic aromatic hydrocarbons (CP-PAHs) based on a tetracene core have been developed and shown to be a bridge between the previously reported anthracene and pentacene cores. These tetracene derivatives were prepared by palladium-catalyzed cyclopentannulation between 5,11-dibromotetracene and two diaryl-ethynylene derivatives. The new compounds relatively small band gaps and have low-energy Lowest Unoccupied Molecular Orbitals (LUMOs) and because of their ability to form cyclopentadienyl anion-like structures that are stabilized by Hückel aromatics.2-4. The photooxidative stability was intermediate to previously prepared CP-PAHs based on anthracene and pentacene derivatives. Scholl cyclodehydrogenation of pendant aryl groups led to materials that quickly form endoperoxide products.5, 6 The general photostability of the cyclopentannulated structures match those of traditional acenes (e.g., CP-anthracene > CP-tetracene > CP-pentacene). Moreover, this dissertation will discuss our efforts to use these tetracene derivatives (and others) to form new bowl-shaped molecules. In addition, this dissertation describes efforts towards the development of supramolecular materials based on secondary bonding in hypervalent iodine systems. Star shaped polymers with a core based on a hypervalent iodine macrocycle (HIM) based on amino acid derived benziodazoles was prepared. An arm-first and core-first approach was used to combine the HIM with an atom transfer radical polymerization (ATRP) initiator to form polystyrene arms. While the desired star polymers were observed by gel permeation chromatrography (GPC), the core HIM were found to degrade under the testing conditions and showed large amount of monomer. A description of our synthetic routes to these materials and the attempts at characterization of this system is described. Lastly, this dissertation describes the development of new anolytes for redox flow batteries. A series of pyrilium based materials that can undergo redox reactions were developed and screened for incorporation into flow batteries owing to their reversibility in redox reactions and the relatively high solubility in acetonitrile. However, cyclic voltammetry, spectroelectrochemical analysis, and bulk electrolysis studies have shown that these species are not stable enough to be considered good candidates as anolytes. To address these stability issues, a series of pyridinium anolyte systems that contain bulky isopropyl or t-butyl groups were prepared and evaluated. Unfortunately, the long term stability in the pyridinium species were also found to be unsatisfactory, which clearly demonstrates the importance of electron withdrawing groups to be included in the anolyte design.