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Identifier 000445752
Title Νέες φωτοκαταλυόμενες παραγοντοποιήσεις και μηχανιστικές μελέτες των φουλερενίων C60 και C70
Alternative Title Novel photocatalyzed functionalizations and mechanistic studies of fullerenes C60 and C70
Author Μαλλιαρός, Νικήτας Γ
Thesis advisor Ορφανόπουλος, Μιχαήλ
Reviewer Στρατάκης, Εμμανουήλ
Βασιλικογιαννάκης, Γεώργιος
Μήλιος, Κωνσταντίνος
Νεοχωρίτης, Κωνσταντίνος
Βουγιουκαλάκης, Γεώργιος
Ταγματάρχης, Νικόλαος
Abstract This dissertation describes the study of new photochemical methods for the chemical modification of fullerenes C60 and C70, leading to the addition of a variety of organic compounds, including phthalides, fluorenes, amides and lactams, aldehydes and alcohols. These reactions occur in the presence of the polyoxometalate catalyst (n-Bu4N)4W10O32 (tetrabutylammonium decatungstate, TBADT) and lead to the single-step formation, isolation, and characterization of novel fullerene adducts. Furthermore, deuterium kinetic isotope effect studies are utilized for the thorough investigation of the mechanistic aspects of these reactions. In the First Chapter, a new photochemical single addition of o-phthalaldehyde to [60]fullerene, is described. This reaction proceeds regioselectively under ambient light and room temperature, affording the corresponding adduct through a one-step high-yield process. A detailed mechanism for this reaction is proposed. Moreover, a new TBADT-photocatalyzed method for the single-step, high yield, radical addition of phthalides to C60 is described. The structural assignment of these compounds has been accomplished by the combined use of FT-IR, UV/Vis and different NMR spectroscopic techniques, as well as by HRMS analysis. Also, deuterium kinetic isotope effect studies, as well as the use of deuterated solvents, are employed to probe the mechanistic aspects of these reactions. The results of this study have been published in the European Journal of Organic Chemistry: https://chemistryeurope.onlinelibrary.wiley.com/doi/abs/10.1002/ejoc.201901363 In the Second Chapter, a convenient, highly efficient, single-step, decatungstate-mediated chemical methodology to functionalize [60]fullerene with lactones is demonstrated. In several cases, the forming radicals are found in more than one sites of the lactone ring, leading to the formation of a corresponding number of fullerene adducts, all of which have been successfully characterized. In the case of two addition examples, a common, unexpected secondary fused C60-cyclopentanone product was recorded. The mechanism of this reaction has been disclosed. The results of this study have been published in the Journal of Organic Chemistry: https://pubs.acs.org/doi/10.1021/acs.joc.1c00954 In the Third Chapter, a simple photochemical methodology for the direct covalent coupling of C60 and substituted fluorenes is presented, leading to the synthesis of Fluorene-C60 dyads, namely 1-fluorenyl-2-hydro-[60]fullerenes. This class of derivatives display a high range of interesting and promising properties in photovoltaics and plastic solar cells. The scope and mechanism of this new reaction have been examined, via the utilization of deuterated fluorenes. The high primary kinetic isotope effect measurements signify the presence of a stepwise mechanism in which the hydrogen-atom abstraction is the rate-determining step of the reaction and disclose information about the geometry of the transition state. The results of this study have been published in the European Journal of Organic Chemistry: https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/ejoc.202100900 In the Fourth Chapter, a simple free-radical approach for the activation of the C–H bond of the N-methyl group in amides and lactams (β- to ε-) is presented. This method utilizes a wide variety of amide and lactam radicals through a hydrogen atom abstraction process mediated by decatungstate. The selective mono-addition of these radical species to C60 enables the simple, selective functionalization of C60 in high yields and low reaction times. The deuterium kinetic isotope effects were measured. Moreover, a mechanistic kinetic approach of the photocatalyzed coupling of amides to C60 was utilized. The free energy rotation barrier (ΔG ) and the Tc (Coalescence Temperature) in one of the C60-amide adducts were experimentally measured, with the use of Dynamic NMR spectroscopy (DNMR). In the Fifth Chapter, a novel, single-step, general TBADT-photocatalyzed method for the addition of a range of aldehydes, alcohols, amides and lactams to the structurally more complex C70, in medium to good yields, is presented. Relatively to the class and reactivity of the substrates, three or four out of the five possible regioisomers I–V were recorded. In each case, full structural characterization of each isomer I–IV was achieved, and their relative percentages were calculated with 1H NMR spectroscopy. The structural assignment of all aforementioned compounds of the current dissertation has been accomplished by the combined use of FT-IR, UV/Vis and different NMR spectroscopic techniques, as well as by HRMS analysis.. All mechanistic studies propose the same mechanistic pattern of the aforementioned addition to C60, regardless of the organic substrates used. First, visible light irradiation of TBADT generates the excited state W10O325-. Subsequently, H-atom abstraction from the substrate provides the one-electron reduced form of decatungstate (W10O325-) and the corresponding C-centered radicals. Simultaneous excitation of C60 to the excited state 3C60* reproduces W10O32.4- via an electron transfer procedure, reaching to a complete catalytic cycle. Consequently, the electron transfer reduction of 3C60* gives the fullerene radical anion (C60•−), which is coupled with the substrate radical to produce the desired fullerene adducts.
Language Greek
Subject Amides
Catalysis
Decatungstate anion (W10O324-)
Fluorenes
Free-radicals
Fullerenes
Lactams
Lactones
Photochemistry
Phthalides
Αμίδια
Αντιδράσεις ελευθέρων ριζών
Δεκαβολφραμικό πολυοξοανιόν (W10O324-)
Κατάλυση
Λακτάμες
Λακτόνες
Φθαλίδια
Φλουορένια
Φουλερένια
Φωτοχημεία
Issue date 2023-04-05
Collection   School/Department--School of Sciences and Engineering--Department of Chemistry--Doctoral theses
  Type of Work--Doctoral theses
Permanent Link https://elocus.lib.uoc.gr//dlib/c/f/a/metadata-dlib-1644309214-651858-8125.tkl Bookmark and Share
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