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Title: Photochemical Reaction of Covalent Organic Frameworks: Probing the Changes in Surface Area and Topology of the Frameworks
Creator: Ye, Yuxin
Date: 2019
Description: Covalent organic frameworks (COFs) are a new class of 2-dimensional or 3-dimensional polymers that have rigid and porous structures. COFs are...
Show moreCovalent organic frameworks (COFs) are a new class of 2-dimensional or 3-dimensional polymers that have rigid and porous structures. COFs are widely applied in gas storage, catalysts, photo conductivity, and drug delivery. Since the applications of COFs are highly related to their structures, it is necessary to learn the stability of COFs under certain conditions. In this research, the stability of COFs towards light was mainly focused on. A new tetraphenyl substituted ketone based COF was synthesized and characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, ultraviolet-visible spectroscopy, and powder X-ray diffraction. Infrared spectra proved that this new COF can undergo Norrish type I reaction to release carbon monoxide under UV irradiation, while main structure of this COF was not broken. This thesis will detailly discussed the synthesis and characterization of this new COF, as well as the building blocks, linkers, and other precursors. This thesis will give some inspirations in the study of energy transfer in covalent organic frameworks.
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Title: QUINODIZATION REACTION OF NAPHTHALENE DIIMIDES TO AFFORD NOVEL P-NAPHTHOQUINODIMETHANE LIGHT-HARVESTING CHROMOPHORES: AROMATICITY, PHOTOPHYSICS AND APPLICATION FOR PHOTON UPCONVERSION
Creator: Shokri, Siamak
Date: 2018
Description: ABSTRACT The chemistry and aromaticity of polycyclic benzenoid hydrocarbons have been a topic of intensive investigations since the early 19th...
Show moreABSTRACT The chemistry and aromaticity of polycyclic benzenoid hydrocarbons have been a topic of intensive investigations since the early 19th century. The concept of aromaticity has played a crucial role in organic chemistry and related fields; and it expanded very rapidly for its ability to explain the stability, electronic structures and physical properties of π-conjugated molecules. Besides benzenoid structures, chemists have also investigated quinoidal systems, which have been shown to exhibit unique aromaticity and physical properties in the ground state. Notably, it is customary to draw quinoidal polycycles as a mixture of closed– and open–shell structures. While closed–shell quinoids do exhibit interesting physical and electronic properties, the open–shell forms can be related to benzenoids with the presence of radicals or unpaired electrons. In this context, it has been demonstrated that open–shell quinoids can have both singlet and triplet multiplicity in their ground state. In this thesis, I will demonstrate that this feature can be tuned/suppressed through clever design of the molecular framework that contains a quinoidal moiety. Often, quinoids can be labeled as aromatic like benzenoids or (anti)/pro-aromatic depending on the molecular framework. Before labeling a quinoidal compound as aromatic or (anti)/pro-aromatic, it is important to define the different aromaticity rules and their influence on the corresponding physical and electronic properties of the system(s) of interest. Chemists have relied on two main aromaticity rules (Hückel vs. Baird) to predict the nature, electronic, and physical properties of quinoidal structures and related systems. We proposed and synthesized novel quinoidal naphthalene derivatives (QDM) that exhibit “compromised” aromaticity in the ground state. A combination of computation and photophysical methods were employed to: i) decipher the reaction mechanism during the formation of the new poly-heterocyclic structures, ii) investigate their ground state and excited state opto-electronic properties, and iii) explore the nature and aromaticity of the corresponding excited state species. Additionally, the QDM was used as light-harvesting triplet sensitizers to achieve photon upconversion. This dissertation will first present a historical perspective in the investigation of various polycyclic aromatic systems that exhibit interesting aromaticity. Then, in chapter 2, I will detail the synthetic route and corresponding mechanism during the preparation of thio-QDM. The characterization and photophysical properties including the transient absorption spectra and excited state dynamics and kinetics of these chromophores will also be discussed. In chapter 3, I will discuss the use of QDM as light-harvesting energy donor to sensitize perylene and achieve triplet-triplet annihilation photon upconversion. The mechanism of this non-linear photophysical process will also be highlighted. Finally, the conclusion chapter will introduce future perspectives in the synthesis of derivatives of QDM.
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Title: Synthesis and Photophysical Characterization of Novel Aromatic Triplet Dyes for Photodynamic Therapy Applications
Creator: Morgan, Jayla A
Date: 2022
Description: Photodynamic therapy is a biomedical approach to treating specific types of cancerous tumor cells and harmful bacteria. The core principle of...
Show morePhotodynamic therapy is a biomedical approach to treating specific types of cancerous tumor cells and harmful bacteria. The core principle of photodynamic therapy involves the usage of a photosensitizer, which is an agent with the capability of transforming molecular, triplet state oxygen, into a reactive oxygen species upon a reaction with near-infrared (NIR) light. The reactive oxygen species has been demonstrated to cause apoptosis among harmful cells without damaging cancer free cells. The effectiveness of photodynamic is highly dependent upon the identity of the photosensitizer; a powerful and efficient photosensitizer should be non-toxic, exhibit high light absorption capabilities, and should produce large amounts of the reactive oxygen species. A novel chromophore bis-iodo-dipyrrolonaphthyridine-dione was demonstrated to have all vital characteristics of an ideal photosensitizer, however produced low amounts of the reactive oxygen species of interest due to the chemical instability of a carbon-halogen bond present in the molecule. Various subsequent halogenations (bis-bromo and bis-chloro) completed in order to remedy this instability revealed specific regioselectivity in regards to the dipyrrolonaphthyridinedione parent that are exhibited upon substituents effects by the substrate, electronic effects exhibited by the reagents of interest, and overall photophysical characterization of the molecules.
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Title: Synthesis and Photophysical Characterization of Novel Organic Triplet Donor–Acceptor Dyads for Light-Harvesting/Modulation Application
Creator: Yun, Young Ju
Date: 2022
Description: Donor–acceptor chromophoric systems (D–A) are important scaffolds for several light-harvesting/initiated processes and devices, including...
Show moreDonor–acceptor chromophoric systems (D–A) are important scaffolds for several light-harvesting/initiated processes and devices, including light-emitting diodes, photo-catalytic/redox systems, and photovoltaic cells. It has been hypothesized that for efficient photophysical processes (viz. energy/charge-transfer or excited-state interactions); it is ideal to tether the donor and acceptor chromophores into molecular dyads. To this end, I devised and synthesized several dyads by tethering an organic triplet energy donor and various polyaromatic chromophores (e.g., perylene derivatives and anthracene derivatives) onto a conjugated-/non-conjugated-linker (phenylene- and triptycene- linker, respectively). During the 4-5 years of my Ph.D., I synthesized a total of five (5) dyads: o–, p–3, and dyads 3–5. These systems were fully characterized using different spectroscopy tools/techniques. The spectroscopy investigations of the dyads have allowed me to decipher two important energy transfer pathways: through-bond and through-space with the phenylene linker and only through-space energy with the triptycene linker. Furthermore, the investigations led to the discovery that geometrical features such as face-to-face (co-facial) or slip-stacked interactions between the donor and acceptors chromophores might dictate the dynamic/kinetic of light-induced energy transfer in the dyads. Findings from my graduate research project paved the way for developing molecular engineering studies for light-harvesting/modulation applications.Subsequently, I was able to employ the dyads of my interest to achieve intramolecular and intermolecular triplet energy transfer (TEnT) triplet-triplet annihilation-based photon upconversion (TTA-PUC).
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