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The synthesis and characterizations together with the electrochemical behavior, UV-Vis spectroscopy, and photophysical properties of the multinuclear supramolecule assembled from the 1,1'-bis(terpyridylethynyl)triferrocene (tpy-C¡ÝC-(fc)3-C¡ÝC-tpy) redox-active spacer with ruthenium centers are described.

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Structural determinations and electrochemical properties in the series of multinuclear ferrocenyl-ethynyl complexes with formula [(£b5-C5(CH3)5)(P2)MII-C¡ÝC-(fc)n-C¡ÝC-MII(P2)(£b5-C5(CH3)5)] (fc = ferrocenyl; M = Fe(II), Ru(II), Os(II); R = H, CH3; P2 = Ph2PCH2CH2PPh2 (dppe)) are reported. Complexes with more electron-rich ligand environment, were prepared with regard to the understanding of electronic coupling mechanism. These complexes undergo sequential reversible oxidation events from -0.2 V to 1.0 V referred to the Ag/AgCl electrode in anhydrous CH2Cl2 solution and the low-pontential waves have been assigned to the end-capped metallic centers. The magnitude of the electronic coupling between two terminal metallic centers in the series of complexes was estimated by electrochemical technique. Based on the correlation between the £GE1/2 values and the second redox potentials of the end-capping metallic centers in the series of complexes, a qualitative explanation for the different magnitude of the electronic coupling is given.

Substrates with localized, organic radicals have the ability to attack `inert' surfaces to form covalent bonds between the substrate and an atom at the surface. These radicals can be generated in electrochemical experiments with substrates bearing an electroactive moiety. The moiety after oxidation (loss of an electron) or reduction (gain of an electron) generates the active radical. Electron transfer reactions at an electrode surface generate a high population of these radicals, thereby facilitating attachment. The electrochemical oxidations of compounds containing terminal alkynes and alkenes were found to be effective methods for covalent attachment to glassy carbon, gold, and platinum electrodes. Modified electrodes were studied for their fundamental electrochemistry with an emphasis on organometallics at the surface and to determine the effect of weakly coordinating anions in heterogeneous electrochemistry. Ferrocene, Fe(η5-C5H5)2, was employed predominantly in this research, as it has robust neutral and cationic states, making it a superior electron transfer agent. A number of other compounds prominent in organometallic electrochemistry, such as ruthenocene (Ru(η5-C5H5)2), cymantrene (Mn(η5-C5H5)(CO)3), cobaltocenium ([Co(η5-C5H5)2]+), and benzene chromium tricarbonyl (Cr(η6-C6H6)(CO)3), were also studied at modified surfaces. A novel method was developed employing the anodic oxidation of ethynyl-lithium compounds to modify electrodes. Oxidation of the carbon-lithium bond leads to an alkyne radical and the loss of lithium ions to solution. The desired radical can be formed either by intramolecular electron-transfer mediation by pendant ferrocenium ions or by the direct oxidation of the ethynyl-lithium bond. These experiments successfully led to the appearance of new surface waves at the electrode. The new surface waves were assigned to the parent molecule of interest based on its electrochemical properties, i.e. its potential, and the electrochemical and chemical reactivity of the redox process. A second general method was developed for terminal alkynes and alkenes which eliminated the need for chemical pre-treatment and lithiation of the alkyne. The direct oxidation of unsaturated carbon-carbon bonds at higher potentials forms the active radical after loss of a proton. The direct oxidation was extended to the organic compound, tetraphenylporphyrin. Porphyrins are a widely used molecular scaffold in naturally occurring compounds such as chlorophyll and heme, and can be applied in optics and electronics due to their intense optical properties. These two approaches hold promise as general anodic methods for electrode modification, and for applications in chemical analysis and catalysis.

Doctor of Philosophy / Department of Chemistry / Sundeep Rayat / Sundeep Rayat / This dissertation focused on the synthesis of 1-(2-ethynylphenyl)-4-phenyl tetrazole-5-thione derivatives 1 and evaluating their potential as a new class of photoactivated DNA cleaving prodrugs. We hypothesized that light activation of 1 would cause the decomposition of the tetrazolethione ring system to enyne-carbodiimide 2 with simultaneous loss of dinitrogen and sulfur via 1,3-triplet biradicals 1′, which would be spontaneously followed by Schmittel cyclization to indoloquinolines 3 via benzofulvene type biradicals 2′. The biradicals 1′ and 2′ would have the potential to cause DNA cleavage by abstracting hydrogens from its sugar phosphate backbone, analogous to the mechanism of action of naturally occurring enediyne antitumor antibiotics. Note that our proposed prodrugs contained a 1,4-diaryl tetrazolethione functionality and a direct synthetic route for their construction was lacking in the literature despite their wide spread applications. Therefore, our initial efforts were directed towards developing a general strategy to obtain these ring systems. We employed a highly versatile and efficient copper mediated N-arylation to first obtain a series of 1,4-diaryl tetrazol-5-ones which were thionated with Lawesson’s reagent to afford the corresponding 1,4-diaryl tetrazole-5-thiones in moderate yields. Specifically, the synthesis of 1 involved Sonogashira coupling of the obtained 1-(2-bromophenyl)-4-phenyl-1H-tetrazole-5(4H)-thione with the appropriate ethynyl compounds (Chapter 2). Since the tetrazole ring is an important structural component in many biologically and medicinally relevant compounds, we were interested in evaluating the anticancer activity of these compounds in the absence of photochemical activation. The moderate IC50 values against leukemia and breast cancer cell lines showed that the anticancer activity of these compounds prior to photoirradiation was minimal (Chapter 3). Independent studies have shown that the photodecomposition of tetrazolethiones gives carbodiimides via biradicals, and photocyclization of enyne-carbodiimide forms indoloquinoline also via biradicals. However, it was not known whether these two photoreactions could happen sequentially in one pot with one light source from a substrate like 1, generating biradicals 1′ and 2′ which could later be employed for DNA photocleavage as hypothesized. Therefere, we photolysed 1 in acetonitrile, and our results show clean formation of a mixture of enyne-carbodiimides and indoloquinolines via biradicals 1′ and 2′ (Chapter 4). Finally, we investigated DNA photocleavage by 1 at 350 nm and our results showed significant DNA cleavage in concentrations as low as 100 μM (Chapter 5).

Darbo tikslas – ištirti heterociklinių junginių, gretimose padėtyse turinčių etinil– ir formilfragmentus, ciklizacijos reakcijas su įvairiais nukleofiliniais reagentais. Darbo metu buvo rastas naujas ir efektyvus pirido[4,3–d]pirimidinų sintezės būdas kurio esmė yra 4–ariletinil–5–pirimidinkarbaldehidų terminė ar mikrobangų inicijuojama reakcija su tret–butilaminu. Parodyta, kad 2–alkinilchinolin–3–karbaldehidai dalyvauja trikomponentinėse reakcijose su pirmininiais aminais ir C– bei P-pronukleofilais sudarydami 1,2–dihidrobenzo[b][1,6]naftiridinus. Pasiūlytas naujas, universalus ir efektyvus būdas benzanuliuotoms sistemoms sintetinti panaudojant metilmerkaptoacetato kalio druską metanolyje. Rasti regioselektyvūs 5,7–dihidrofuro[3,4–d]pirimidinų, 5(H)–pirano[4,3–d]pirimidinų, 1,3–dihidrofuro[3,4–b]chinolinų ir 1H–pirano[4,3–b]chinolinų sintezės būdai tandeminių 5–egzo–dig ir 6–endo–dig ciklizacijos reakcijų pagalba. Rastas efektyvus būdas 2–(2–aril(alkil)–2–oksoetil)–1H–indol–3–karbaldehidams sintetinti iš 2–alkinil–1H–indol–3–karbaldehidų ir metanolio katalizuojant sidabro druskoms. Parodyta, kad 2–alkinilchinolin–3–karbaldehidai reaguodami su dimetilfosfitu bazinėje terpėje sudaro prisijungimo produktus dimetilhidroksi– (2–pakeistus-chinolin–3–il)metilfosfonatus. Pastarieji, esant bazės pertekliaus, persigrupuoja į atitinkamus dimetil–(2–pakeistus-chinolin–3–il)metilfosfatus. Nustatyta, kad 2–(2–piridinil)etinilchinolin–3–karbaldehidas ir 6–ariletinilpirimidin–... [toliau žr. visą tekstą] / The main aims of this investigation were to investigate cyclization reactions of electron–deficient 6–alkynylpyrimidine–5–carbaldehydes and 2–alkynylquinoline–3–carbaldehydes, and electron–rich 2–alkynylindole–3–carbaldehydes and 2–alkynylthiophene–3–carbaldehydes with N–, S–. O–, C– and P–nucleophiles. It was found, that 6–arylethinylpyrimidine–5–carbaldehydes under the treatment with tert–butylamine underwent thermal or microwave–induced cyclization reaction to form pyrido[4,3–d]pyrimidines. A novel and fast synthetic method for preparation of 1,2,3–trisubstituted 1,2–dihydrobenzo[b][1,6]naphthyridines by means of a three–component reaction between 2–alkynylquinoline–3–carbaldehydes, primary amines and C– or P–pronucleophiles was developed. It was showed, that methyl mercaptoacetate was able to trigger a novel benzannulation reaction of the starting materials. Novel, concise and regioselective synthetic methods of 5,7–dihydrofuro[3,4–d]pyrimidine, 5H–pyrano[4,3–d]pyrimidine, 1,3–dihydrofuro[3,4–b]quinolines and 1H–pyrano[4,3–b]quinolines frameworks via regioselective acetalisation/cyclization reactions of 2,4–disubstituted 6–phenylethynylpyrimidine–5–carbaldehydes and 2–alkynylquinoline–3–carbaldehydes were developed. A relatively short and efficient synthesis of 2–(2–oxoethyl)–1H–indole–3–carbaldehydes via tandem 6–endo–dig cyclization from 2–alkynylindole–3–carbaldehydes was developed. It was found that 2–alkynylquinoline–3–carbaldehydes react with dimethylphosphite in... [to full text]

The main aims of this investigation were to investigate cyclization reactions of electron–deficient 6–alkynylpyrimidine–5–carbaldehydes and 2–alkynylquinoline–3–carbaldehydes, and electron–rich 2–alkynylindole–3–carbaldehydes and 2–alkynylthiophene–3–carbaldehydes with N–, S–. O–, C– and P–nucleophiles. It was found, that 6–arylethinylpyrimidine–5–carbaldehydes under the treatment with tert–butylamine underwent thermal or microwave–induced cyclization reaction to form pyrido[4,3–d]pyrimidines. A novel and fast synthetic method for preparation of 1,2,3–trisubstituted 1,2–dihydrobenzo[b][1,6]naphthyridines by means of a three–component reaction between 2–alkynylquinoline–3–carbaldehydes, primary amines and C– or P–pronucleophiles was developed. It was showed, that methyl mercaptoacetate was able to trigger a novel benzannulation reaction of the starting materials. Novel, concise and regioselective synthetic methods of 5,7–dihydrofuro[3,4–d]pyrimidine, 5H–pyrano[4,3–d]pyrimidine, 1,3–dihydrofuro[3,4–b]quinolines and 1H–pyrano[4,3–b]quinolines frameworks via regioselective acetalisation/cyclization reactions of 2,4–disubstituted 6–phenylethynylpyrimidine–5–carbaldehydes and 2–alkynylquinoline–3–carbaldehydes were developed. A relatively short and efficient synthesis of 2–(2–oxoethyl)–1H–indole–3–carbaldehydes via tandem 6–endo–dig cyclization from 2–alkynylindole–3–carbaldehydes was developed. It was found that 2–alkynylquinoline–3–carbaldehydes react with dimethylphosphite in... [to full text] / Darbo tikslas – ištirti heterociklinių junginių, gretimose padėtyse turinčių etinil– ir formilfragmentus, ciklizacijos reakcijas su įvairiais nukleofiliniais reagentais. Darbo metu buvo rastas naujas ir efektyvus pirido[4,3–d]pirimidinų sintezės būdas kurio esmė yra 4–ariletinil–5–pirimidinkarbaldehidų terminė ar mikrobangų inicijuojama reakcija su tret–butilaminu. Parodyta, kad 2–alkinilchinolin–3–karbaldehidai dalyvauja trikomponentinėse reakcijose su pirmininiais aminais ir C– bei P-pronukleofilais sudarydami 1,2–dihidrobenzo[b][1,6]naftiridinus. Pasiūlytas naujas, universalus ir efektyvus būdas benzanuliuotoms sistemoms sintetinti panaudojant metilmerkaptoacetato kalio druską metanolyje. Rasti regioselektyvūs 5,7–dihidrofuro[3,4–d]pirimidinų, 5(H)–pirano[4,3–d]pirimidinų, 1,3–dihidrofuro[3,4–b]chinolinų ir 1H–pirano[4,3–b]chinolinų sintezės būdai tandeminių 5–egzo–dig ir 6–endo–dig ciklizacijos reakcijų pagalba. Rastas efektyvus būdas 2–(2–aril(alkil)–2–oksoetil)–1H–indol–3–karbaldehidams sintetinti iš 2–alkinil–1H–indol–3–karbaldehidų ir metanolio katalizuojant sidabro druskoms. Parodyta, kad 2–alkinilchinolin–3–karbaldehidai reaguodami su dimetilfosfitu bazinėje terpėje sudaro prisijungimo produktus dimetilhidroksi– (2–pakeistus-chinolin–3–il)metilfosfonatus. Pastarieji, esant bazės pertekliaus, persigrupuoja į atitinkamus dimetil–(2–pakeistus-chinolin–3–il)metilfosfatus. Nustatyta, kad 2–(2–piridinil)etinilchinolin–3–karbaldehidas ir 6–ariletinilpirimidin–... [toliau žr. visą tekstą]

La demande énergétique mondiale toujours en croissance, combinée aux préoccupations environnementales, constitue le moteur qui anime la recherche de nouvelles énergies. La fusion thermonucléaire est une des technologies qui offrent la possibilité d'une production d'énergie abondante, sûre et non polluante ; cependant son apprivoisement n'est pas encore au point ! La présence d'impuretés dans les plasmas est un des obstacles majeurs à vaincre pour atteindre les conditions nécessaires pour que la fusion thermonucléaire devienne suffisamment efficace. Leur densité dans le plasma dépend des matériaux de revêtement des parois et du contrôle des conditions aux limites, conditions qui définissent leur processus de génération et leur diffusion dans la région centrale. Les pertes énergétiques ont été considérablement réduites par l'utilisation de revêtements à basse charge nucléaire (Z), principalement ceux à base de carbone (comme le graphite). Ainsi, les chercheurs se sont intéressés aux effets des impuretés hydrocarbonées se dégageant des parois des réacteurs, à savoir leur structure et les voies de leur fragmentation, en particulier, les caractéristiques de leurs processus collisionnels avec les autres constituants du plasma. L'ion moléculaire est un composant essentiel de nombreux plasmas astrophysiques où l'ionisation et la dissociation se font principalement avec des électrons ; sa concentration est élevée dans l'ionosphère, région de l'atmosphère située à une altitude comprise entre 90 et 250 Km. Le rôle important joué par cet ion dans la modélisation ionosphérique nous a mené à réaliser une série de mesures des sections efficaces de ses différents processus collisionnels par impact d'électrons. La majorité des travaux expérimentaux antérieurs ne concernait que la molécule neutre . Ce travail de thèse a porté sur l'étude expérimentale de l'ionisation simple, de l'excitation dissociative et de l'ionisation dissociative par impact d'électrons des ions hydrocarbonés polyatomiques et et de l'ion diatomique . Nous avons utilisé la technique des faisceaux croisés et animés pour mesurer les sections efficaces absolues de ces processus. Nous avons d'abord mesuré les distributions d'énergie cinétique des produits de ces processus dans le référentiel du laboratoire, en fonction du champ magnétique d'analyse, pour différentes valeurs d'énergie d'électrons. Ensuite, nous avons mesuré les sections efficaces apparentes pour les mêmes processus en fonction de l'énergie des électrons. Concernant les processus dissociatifs, la mesure des distributions d'énergie cinétique des fragments dans le référentiel du laboratoire a montré que ces fragments sont, généralement, distribués dans des gammes angulaires et énergétiques larges et que leurs divergences angulaires, dans la plupart des cas, excèdent l'ouverture de la fente d'analyse et en conséquence, leur transmission n'est que partielle. Nous avons alors calculé leurs coefficients de transmission en fonction de l'énergie des électrons, et nous avons corrigé les sections efficaces apparentes, pour chacun des processus dissociatifs. Nous avons ainsi pu obtenir les sections efficaces absolues de plusieurs voies dissociatives. Nous avons identifié leur seuil d'apparition en tenant compte des structures de l'ion moléculaire primaire et des ions produits. Nous avons déterminé aussi les distributions d'énergie cinétique des fragments produits dans le référentiel du centre de masse à partir des distributions énergétiques observées dans le référentiel du laboratoire, nous avons ainsi pu estimer l'énergie maximale libérée lors de chacun des processus dissociatifs. Les résultats ont montré que la section efficace de l'ionisation simple est faible en comparaison avec les sections efficaces d'excitation et d'ionisation dissociative. Celle-ci dépend du nombre, généralement réduit, des états liés stables de l'ion doublement chargé. Ils ont montré aussi que les courbes des sections efficaces des processus d'excitation dissociative et d'ionisation ont une allure très différente. Dans le premier cas, elle augmente abruptement au voisinage du seuil alors que dans le second cas, elle augmente progressivement avec l'énergie des électrons. Pour les processus de dissociation, nous avons besoin d'une analyse angulaire et d'une détection en coïncidence des fragments produits, permettant ainsi de déterminer la nature exacte du mécanisme et d'identifier avec plus de précision l'état ou les états moléculaires impliqués dans chacune des réactions. Les résultats obtenus sont concluants et ont permis d'améliorer l'étude théorique semi-classique menée par Probst et Märk (2004) concernant l'ionisation de . Ils ont montré aussi que les prédictions empiriques de Janev et Reiter (2002) relatives aux familles d'hydrocarbures ne sont pas encore au point. Elles sont en désaccord avec nos résultats, montrant ainsi qu'il y a grand besoin d'autres études expérimentales des processus collisionnels des hydrocarbures et d'autres ions moléculaires avant de pouvoir formuler une quelconque loi d'échelle ou une théorie capable de prédire le comportement de tels ions moléculaires.

Electrochemical potentials of a series of anthraquinone derivatives were studied in both aqueous solution and acetonitrile. The long term goal of this work was to find derivatives which could be reduced easily for studies of photoinduced electron transfer in DNA. Our immediate goal was to find the substitution group that gave the least negative redox potential value. Of all derivatives studied, the anthraquinone imides as a class had the least negative redox potentials, in the range of -0.600 to -0.550 V vs. SCE. One of the anthraquinones studied, one derivative (deoxyadenosine conjugated with an ethynyl linker to an anthraquinone with two ester substituents) was also in this range. A study of a series of anthraquinones conjugated with ethynyl and ethanyl linkers showed that the ethynyl linker was more effective than the ethanyl linker in lowering the redox potential of anthraquinone.