7 research outputs found

    Part 1: Towards the Synthesis of Pyrene Zigzag Cyclacenes, Part 2: New Methods for the Synthesis of Conjugated Polymers

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    Part 1: Carbon nanotubes (CNTs) are allotropes of carbon that have emerged as candidates for implementation in electronic devices ranging from transistors to solar cells. Unfortunately, the behavior of CNTs is highly dependent on their structure and modern synthetic methods for generating CNTs are not able to provide uniform samples for electronic applications. Recently, the synthesis of cycloparaphenylenes (CPPs), which closely resemble metallic CNTs, has been elucidated and has since been further expanded to allow for the CPPs of varying diameters and subunits. More importantly, CPPs were also shown to allow for the controlled bottom-up synthesis of CNTs, opening the door towards the concise synthesis of CNTs. Herein, we will outline our synthetic attempts towards the synthesis of zigzag cyclacenes and how the creation of a zigzag nanobelt could bring forth the defined synthesis of semiconducting zigzag nanotubes. Drawing inspiration from previous attempts at cyclacenes and the successful synthesis of CPPs, we set out to construct a zigzag macrocycle using a Diels-Alder approach with pyrene as the backbone of the cycle. We were able to successfully construct the cyclic precursor to the cyclacene following numerous attempts; however, isolation of the fully aromatized product was not accomplished because the strain exhibited by the cycle led to an over reduction. Our search to create cyclacenes led us towards phosphonium salts as a new method for the mild creation of benzyne. Unfortunately, the phosphonium benzyne performed poorly due to regioselectivity issues, but in trying to create the aryl phosphonium salts, we created a new route towards these compounds. Herein, we will describe our development of a metal free synthesis of aryl phosphonium salts. When aryl halides are irradiated with UV light in the presence of a phosphine, the two species can couple leading to the formation of the phosphonium salt. The reaction is amenable to a variety of phosphines and can proceed with aryl chlorides, iodides, bromides, and pseudohalides. Part 2: Conjugated polymers have gained a great deal of interest as these compounds can be used as active materials and enable the creation of lightweight, flexible, and low-cost electronic devices. Critical to the advancement of these technologies is the creation of new synthetic methods and facile access to material. Herein, we will outline the development of new synthetic techniques for the creating conjugated polymers. First, we will discuss the development of a new metal free dehydrative polymerization of thiazole N-oxides. Drawing inspiration from nature and from the industrial synthesis of commodity polymers, such as PET and nylon-6,6, we developed a new transformation that can dimerize thiazole N-oxides in the absence of a metal with the formal loss of water being the sole byproduct. This methodology was later extended onto bifunctional monomers and allowed for the synthesis of conjugated polymers in quantitative yield and good molecular weights. Secondly, we will discuss the design and synthesis of a new palladium precatalyst for the synthesis of conjugated polymers through direct arylation polymerization. Conjugated polymers are mostly synthesized using transition metal couplings such as Stille or Suzuki couplings; however, these methods require pre- functionalization and can leave behind toxic byproducts. Direct arylation polymerization has recently emerged as a new technique for synthesizing conjugated polymers; however, the nature of the propagating species means that conjugated polymers created this way are more prone to branching/crosslinking defects. We designed a palladium precatalyst specifically for direct arylation polymerization that can reduce unwanted functionalization while providing good molecular weights, high yields, lower loadings, and improved thermal properties

    Exploiting the Potential of Carbon Nanotubes and Fullerenes Through their Interaction with Specially Designed π-Conjugated Iptycenes

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    Electronics have become integrated into every aspect of modern life, from work to leisure we rely on electronics for key tasks in our daily routine. Recent research efforts have seen a push towards flexible electronic devices, creating a plethora of new potential applications. Carbon nanomaterials have emerged as excellent candidates for implementation into flexible electronic devices from transistors to solar cells, but despite their high potential, their commercial relevance has been hampered by several key challenges that have yet been unresolved. Here, I exhibit that through the merging of techniques from organic chemistry and nanoscience, I have been able to overcome several of the practical challenges facing both carbon nanotubes and fullerenes. This has been accomplished through the interaction of these carbon nanomaterials with shape complementary iptycene molecules. The concave shape of iptycenes allows them to interact very strongly with the convex carbon nanotubes and fullerenes. This has led us to develop a new technique for the simultaneous alignment and sorting of carbon nanotubes based on diameter and length, as well as the large-scale purification of fullerenes via flash chromatography. Furthermore, in the search for new iptycene derivatives, a new ligand for the formation of metal-organic frameworks has been discovered and studied

    FERROCENE-FUSED DERIVATIVES OF ACENES, TROPONES AND THIEPINS

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    This research project is concentrated on tuning the properties of small organic molecules, namely polyacenes, tropones and thiepins, by incorporating redox-active transition metal centers π-bonded to terminal cyclopentadienyl ligands. Organometallic-fused acenequinones, tropones, thiepins and cyclopentadiene-capped polyacenes were synthesized and characterized. This work was divided into three parts: first, the synthesis of ferrocene-fused acenequinones, cyclopentadiene-capped acenequinones and their subsequent aromatization to polyacenes; second, the synthesis of ferrocene-fused tropones, thiotropones and tropone oxime; and third, the synthesis of ferrocene-fused thiepins. Ferrocene-fused quinones are the precursors to our target complexes. Our synthetic route to ferrocenequinones involved two-fold aldol condensation between 1,2-diformylferrocene and naphthalene-1,4-diol or anthracene-1,4-diol, and four-fold condensation between 1,2-diformylferrocene and 1,4-cyclohexanedione. Reduction of ferrocene-fused quinones with borane in THF resulted in ferrocene-fused dihydroacenes. Attempts to reduce ferrocene-fused acenequinones with sodium dithionite led to metal-free cyclopentadiene- (Cp-) capped acenequinones. Cp-capped acenequinones were aromatized to bis(triisopropylsilyl)ethynyl polyacenes by using lithium (triisopropylsilyl)acetylide (TIPSC≡CLi) with subsequent dehydroxylation by stannous chloride. The compounds were characterized by using spectroscopic methods and X-ray crystallography. Further, the electronic properties of these compounds were studied by using cyclic voltammetry and UV-visible spectroscopy. Cyclic voltammetry showed oxidation potentials of Cp-capped TIPS-tetracene and bis-Cp-capped TIPS-anthracene as 0.49 V and 0.61 V, respectively (vs. ferrocene/ferrocenium). The electrochemical band gaps were 2.15 eV and 2.58 eV, respectively. Organic thin-film transistor device performance of Cp-capped polyacenes was studied using solution deposition bottom-contact, bottom-gate (BCBG) device architecture and the resulting performance parameters are described herein. Similarly, we are also interested in potential applications of metallocene-fused tropones and derivatives as organic electronic materials. Condensation of 1,2-diformylferrocene with acetone or 1,3-diphenylacetone in the presence of KOH resulted in the ferrocene-fused tropone (η5-2,4-cyclopentadien-1-yl)[(1,2,3,3a,8a-η)-1,6-dihydro-6-oxo-1-azulenyl]iron (1, R = H, E = O) and its 5,7-diphenyl derivative (1, R = Ph, E = O) as previously reported by Tirouflet. The use of piperidine as base resulted in Michael addition of piperidine to one of the carbon-carbon double bonds of the tropones. Lawesson’s reagent converted the ferrocene-fused tropones to either a thiotropone (1, R = H, E = S) or a detached 5,7-diphenylazulenethiol (2). Reaction of the ferrocene-fused thiotropone with hydroxylamine gave the corresponding oxime (1, R = H, E = NOH). Products were characterized by using spectroscopic methods and X-ray crystallography. Their electronic properties were studied by using cyclic voltammetry and UV-visible spectroscopy. The third project involved the two-fold aldol condensation of 1,2-diformylferrocene with dimethylthioglycolate S-oxide in the presence of freshly distilled triethylamine, which gave mono- and di-dehydrated products. Deoxygenation of the ferrocene-fused thiepin S-oxide with 2-chloro-1,3,2-benzodioxaphosphole in the presence of pyridine resulted in the corresponding thiepin. The ester groups of the thiepin and thiepin S-oxide were hydrolyzed under basic conditions to give carboxylic acids, which were converted into acid chlorides using oxalyl chloride. Attempts to decarboxylate the thiepin and thiepin S-oxide diacids resulted in decomposition

    Chemistry & Chemical Biology 2013 APR Self-Study & Documents

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    UNM Chemistry & Chemical Biology APR self-study report, review team report, response to review report, and initial action plan for Spring 2013, fulfilling requirements of the Higher Learning Commission

    Redox-active molecules and polymers with photovoltaic applications

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    The study presented in this thesis provides details regarding the synthesis and characterization of different redox active molecules which can be applied to form the active layer of photovoltaic devices. For example in chapter two, star-shaped thiophene based molecules are described and their electronic and optical properties have been investigated. In chapter three, oligomers featuring bipyridinium units with different thienyl moieties have been successfully synthesized. Preliminary electropolymerization studies are achieved. In chapter four, two different series of powerful push-pull systems containing dimethyaniline DMA moieties as a strong donating group and TCNE or TCNQ as electron accepting groups have been prepared. These series feature quinone and oligothiophene units as supporting acceptor and donor unit. In chapter five, two different series of powerful organic dyes that could improve the efficiency of DSSCs by modulating the absorption of light towards the near-IR region are achieved. The influence of π-conjugated spacers on the optical and physical properties of synthesized dyes has been investigated. Preliminary DSSCs have been fabricated from some of these systems and their properties have been compared to dye N719

    Novel Thieno[3,4-b]pyrazine based π-conjugated polymers for optoelectronic devices

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    Conjugated polymers have attracted considerable attention as a new class of electronic material, since the study of these systems has generated entirely new scientific concepts as well as potential for new technology. Conjugated polymers are organic semiconductors and as such important materials for applications in electronic and photonic devices. Prime examples are polymeric light-emitting diodes, plastic lasers, and polymer based photovoltaic cells, but at least in principle, conjugated polymers should be able to pertain all of the functions an inorganic semiconductor displays, FETs, and may lead in the future to "molecular electronics". The primary advantage of organic polymers over their inorganic counterparts is their ease of processing by dip coating, spin casting, printing, or use of doctor blade techniques. However, conjugated polymers are likewise important as sensory materials for water, organic vapors, and explosives either by fluorescence quenching or in artificial nose devices, which change their conductivity upon exposure to a suitable analyte
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