Compostos porfirínicos desempenham uma grande variedade de funções em sistemas biológicos. Em particular, no processo de respiração e na fotossíntese, dois ou mais macrociclos porfirínicos encontram-se próximos na mesma estrutura protéica. A proximidade e a orientação entre os macrociclos são importantes no tipo de função desempenhada; a disposição cofacial entre os macrociclos é um dos fatores responsáveis pelo processo de transferência de elétrons que ocorre nos fotossistemas de organismos fotossintetizantes. Vários estudos têm sido realizados in vitro, com o objetivo de entender o efeito da proximidade e orientação entre os macrociclos nos processos de transferência eletrônica fotoinduzida que ocorrem durante a fotossíntese. Uma das maneiras de construir sistemas miméticos capazes de armazenar luz e transferir elétrons consiste na formação de pares iônicos entre moléculas que apresentam cargas opostas. Apesar da maior versatilidade desses sistemas, não existem estudos sistemáticos que avaliem os efeitos estruturais provenientes da funcionalização dos macrociclos porfirínicos no processo de formação e nas propriedades espectroscópicas de pares iônicos. Esse trabalho apresenta um estudo sobre a formação de pares iônicos entre metaloftalocianinas aniônicas e uma nova classe de porfirinas catiônicas planares e não planares. Através da determinação dos valores das constantes de formação dos heterodímeros, procurou-se avaliar como as características estruturais/eletrônicas dos substituintes β- e meso- do anel se refletem no processo de formação e nas propriedades espectroscópicas dos agregados. Esses estudos foram realizados em diferentes solventes/misturas de solventes e em diferentes forças iônicas, de modo que foi possível avaliar como a mudança do solvente ou da concentração de eletrólito adicionado se reflete no processo de associação entre espécies de carga oposta. As porfirinas não planares utilizadas derivam de uma classe de porfirinas planares que apresentam grupos benzílicos substituídos ligados aos grupos piridínicos presentes nas posições mesa do macrociclo porfirínico; oito átomos de bromo ligados nas posições β-pirrólicas do macrociclo causam a distorção do anel. A introdução de 8 átomos de bromo nas posições β-pirrólicas do macrociclo porfirínico provoca alterações nas propriedades espectroscópicas e fotofísicas das porfirinas, comparando-se as porfirinas β-octabromadas e seus respectivos análogos não bromados. Essa alterações são decorrentes, tanto da distorção do anel, como do efeito de átomo pesado exercido pelos átomos de bromo. Como principais alterações pode-se citar: (i) deslocamento batocrômico dos máximos de absorção e emissão; (ii) redução significativa nos valores de Φfl; (iii) maiores deslocamentos de Stokes; (iv) diminuição nos valores dos tempos de vida do estado excitado triplete; e (v) em função do tipo de solvente empregado, observa-se a coexistência de duas espécies distintas no estado excitado triplete que decaem com tempos de vida distintos. Os valores de KPI obtidos demonstraram que a associação entre as porfirinas catiônicas e as ftalocianinas aniônicas é dependente de uma série de fatores, e pode ser modulada alterando-se o tipo de substituinte ligado ao macrociclo porfirínico e as características do meio, tais como o tipo de sol vente empregado e a força iônica do meio. Os estudos de associação realizados em DMSO demonstraram que (i) a presença do resíduo benzílico traz interações hidrofóbicas adicionais significativas ao processo de associação; (ii) o impedimento estérico decorrente do maior volume do meso-substituinte predomina sobre os efeitos eletrônicos dos grupos ligados na posição para do anel benzílico; e (iii) diferenças na magnitude da distorção da ligação Ni-N e Cu-N para fora do plano, em função da ligação axial a uma molécula de DMSO, se refletem nos valores de KPI. A partir dos estudos realizados em diferentes misturas de solventes, pôde-se constatar que (i) mudanças na esfera de solvatação das porfirinas em meios com maior concentração de H2O alteram os valores de KPI ao longo da série de porfirinas estudadas; e (ii) a formação de dímeros de ftalocianina compete com a formação do heterodímero ftalocianina/porfirina. O controle da força iônica do meio produz alterações significativas nos valores de KPI ao longo da série de porfirinas estudadas. A partir desses experimentos foi possível avaliar o efeito eletrônico dos grupos ligados na posição para do anel benzílico no processo de associação com as ftalocianinas, em relação à ZnTMPyP. A introdução de átomos de bromo no macrociclo porfirínico produz uma série de alterações no processo de associação entre as porfirinas e as ftalocianinas. Durante a associação entre as ftalocianinas e as Zn(II)porfirinas β-octabromadas que apresentaram maiores desvios com relação à planaridade do anel, observou-se a formação de uma espécie trimérica constituída por duas moléculas de porfirina e uma molécula de ftalocianina. Uma vez que ambos os macrociclos encontram-se coordenados axialmente a uma molécula de DMSO, que inviabiliza a formação de um trímero onde os macrociclos se encontram dispostos cofacialmente, este trímero deve ser formado a partir de uma sobreposição parcial entre os macrociclos de carga oposta. Os estudos de fluorescência demonstraram que ocorre uma eficiente supressão da fluorescência da Zn(II)porfirina após a adição de ftalocianina no meio. Demonstraram ainda que esta supressão ocorre através de um processo estático, devido à formação de um complexo de estado fundamental. A avaliação preliminar dos resultados obtidos durante a caracterização do estado excitado triplete dos heterodímeros CuPcTS/ZnP indica que a espécie transiente monitorada na região de 700nm corresponde ao heterodímero presente em solução. Indica ainda que o estado excitado triplete do heterodímero apresenta um caráter de energia predominantemente da ftalocianina. / Macrocyclic tetrapyrroles, like porphyrin derivatives, occur biologically in many enzymes, heme compounds, and photosynthetic protein as chlorophyll. Particularly in the latter, two chlorophylls adopt a face-to-face conformation to form the so-called special pair, the efficient primary electron-donor in the photosynthetic apparatus. It is known that the cofacial arrangement of chlorophylls is a very important feature, because photosynthetic electron transfer process is a function of macrocycle separation and orientation. The complexity of this process has prompted numerous studies of pairing donor-acceptor molecules to mimic the photosynthetic system and understand how the spatial orientation and proximity between the macrocycles affect the fotoinduced electron transfer process. Spontaneous aggregation between porphyrins and phthalocyanines bearing charged peripheral substituents occurs in solution, and thus, these molecules have been employed to study face-to-face heterodimer bound electrostatically. Despite the fact that these systems share many of the characteristics of naturally occurring special pair, there is no systematic study assessing the structural effects of functionalized porphyrin rings on the association process for anionic macrocycles. This work reports a heterodimer formation between anionic phthalocyanines and a new class of cationic planar and non planar porphyrins. Heterodimers have been characterized by determining the formation equilibrium constants (KPI) in different media and ionic strength. The new class of non planar cationic Zn (II) porphyrins synthesized presents eight bromine atoms attached to the β-pyrrole position of the porphyrin ring, leading to a high degree of distortion. The planar cationic precursor presents substituted benzylic groups attached to the nitrogen atoms of the pyridyl residues located at the meso-porphyrin positions. Both ring distortion and heavy atom effect caused by the introduction of bromine atoms at the macrocycle periphery cause many changes in the spectroscopic and photophysical properties, comparing to the planar precursor. The main differences observed are: (i) batochromic shifts of absorption and emission maxima; (ii) lower fluorescence quantum yields; (iii) larger Stokes shifts; (iv) reduced triplet lifetimes and; (v) depending on the solvent employed, it was observed the coexistence of two distinct species in the excited triplet state that posses different lifetimes. According to the KPI values obtained, it was inferred that the association process can be modulated by changing the meso- and β-substituent attached to the porphyrin ring, and altering medium characteristics. The KPI values obtained in DMSO solution suggest that steric hindrance from benzylic groups overwhelms the additional hydrophobic/eletronic effects from these meso-substituents. When the ionic strength was kept constant, a decrease in the KPI values was observed, as expected to the association between ionic species. It could be noted, therefore, that the additional hydrophobic contribution from benzylic substituent, and also the electronic characteristics of the small groups attached to the benzylic ring affect the association process. From experiments carried out in solvent mixtures, it could be observed that, if the solvent dielectric constant increases, the KPI values decrease. Likewise, changes in the porphyrin macrocycle solvation alter the KPI value through the porphyrin serie studied. Additionally, as the water concentration increases, the phthalocyanine self-association process competes with heterodimer formation. The introduction of bromine at ring periphery changes the association process. The KPI values obtained to the heterodimer formed between the anionic phthalocyanines and the β-octabrominated porphyrins, are about 10 times smaller compare d to the KPI obtained using the planar precursor. It is a consequence of nonplanar distortion, that diminishes the cofacial approximation between the macrocycles. Addi tionally, heterotrimers can be formed by altering the porphyrin concentration - this behavior was not found to the aggregates formed between the phthalocyanines and the planar precursor derivatives at the same condition. Emission studies evidence a ground state complex formation, since the phthalocyanine quenches the Zn (II) porphyrin fluorescence through a static process. The preliminary results obtained to the heterodimer triplet characterization showed that the heterodimer excited triplet state is more delocalized on the phthalocyanine moiety.

A preparação, caracterização e estudo de propriedades moleculares e supramoleculares de meso-tetrapiridilporfirinas modificadas com quatro complexos de cloro(bipiridina) platina(II) ligados às posições meta e para de ligantes piridínicos periféricos, foi objetivo desta tese. As supermoléculas isômeras foram isoladas no estado sólido e extensivamente caracterizados por meio de espectroscopia UV/VIS, FT-IR e RMN de Pt-195, assim como através de TGA e espectrometria de massa com ionização por spray de elétrons, ESI-MS, e técnicas de dissociação induzidas por colisão. Medidas de voltametria cíclica e de espectroeletroquímica foram realizadas para caracterizar os estados redox da porfirina central e dos complexos periféricos, mostrando uma semelhança entre as duas formas isômeras. A maior diferença, entretanto, foi observada nas suas propriedades estruturais, diagnosticadas por modelagem molecular, e refletidas na morfologia dos filmes obtida por meio de técnicas de microscopia de varredura por sonda, SPM, e através da associação com filmes de DNA, monitorada com o auxílio de técnicas de espectroscopia eletrônica e ressonância plasmônica de superfície, SPR. No último caso, o DNA foi imobilizado sobre a superfície do sensor de ouro, usando aminotióis adequados, sendo que a interação do isômero meta conduziu a uma resposta contrastante, relevando uma forte ligação com a cadeia do DNA, provavelmente nas proximidades das fendas estruturais menores desse biopolímero. A interação do isômero para com o DNA foi demasiadamente fraca para ser observada por meio de SPR. A associação molecular das porfirinas tetraplatinadas catiônicas com ftalocianinas aniônicas tetrassulfonadas conduziu à formação de pares iônicos em solução. O filme do isômero para imobilizado sobre eletrodo de carbono vítreo apresentou atividade na redução eletrocatalítica de nitrito. Os trabalhos realizados demonstraram que os novos sistemas supramoleculares derivados de porfirinas e complexos de platina proporcionam interessantes materiais híbridos inorgânico-biológicos contendo DNA e metais nobres, com potenciais aplicações em terapia fotodinâmica, sensoriamento e em dispositivos moleculares. / The synthesis, characterization and investigation of the molecular and supramolecular behaviour of meso-tetrapyridylporphyrins containing four chloro(bipyridine) platinum(II) complexes attached at the meta and para positions of the peripheral pyridine ligands is focused on this thesis. The isomeric supermolecules were isolated in the solid state, and extensively characterized by means of UV-visible, FT-IR and 195Pt NMR spectroscopy, as well as, by TGA and electrospray spectrometry associated with collision induced techniques. Cyclic voltammetry and spectroelectrochemical measurements were performed to characterize the redox sites on the porphyrin and peripheral complexes, revealing a close similarity between the two isomeric supermolecules. Major differences were observed on their structural properties, as demonstrated by means of molecular simulations, and by the morphology of the molecular films probed by SPM techniques, and also by their association with DNA films, which was monitored by means of SPR techniques. In the last case, DNA was first immobilized onto the surface of the gold sensor, using suitable aminothiols and the interaction of the meta-isomer led to a contrasting response, exhibiting a strong binding to the DNA chain, presumably at the proximity of the minor grooves. The interaction of the para-isomer with DNA was too weak to be probed by means of the SPR technique. Molecular association of the tetraplatinum porphyrin species, with tetrasulphonated phtalocyanines, leading to ion pairs in solution, was also investigated. The molecular film of the para-isomer immobilized over glass carbon electrode has shown activity in the electrocatalytic reduction of nitrite. This work on the supramolecular porphyrin platinum species provided new interesting approaches for generating hybrid biological-inorganic systems, containing DNA and noble metals, for sensing applications, and molecular devices.

A química supramolecular representa o caminho mais promissor na rota de desenvolvimento da nanotecnologia devido à maneira especial com que diferentes moléculas interagem, trocando informações e criando estruturas organizadas. Esta tese pretende contribuir para este campo de pesquisa, através do estudo de três derivados terpiridínicos funcionalizados e seus complexos de ferro(II): 4\'-(3- tienil)- 2,2\':6\',2\'\'-terpiridina (titpy), [Fe(titpy)2]2+; 4\'-(4\'-(fenil)- 2,2\':6\',2\'\'-terpiridina (phtpy), [Fe(phtpy)2]2+ e 4\'-(4-bromo-fenil)-2,2\':6\',2\'\'-terpiridina (Br-phtpy), [Fe(Brphtpy)2]2+. A investigação desses complexos foi realizada por métodos espectroscópicos, físico-químicos e computacionais. As propriedades dos complexos sintetizados foram exploradas empregando o conceito de química supramolecular, através da interação dos mesmos com β-ciclodextrina, matriz de gel de pentóxido de vanádio e nanopartículas de ouro. Os novos materiais gerados apresentaram características que tornam possível a sua aplicação em diferentes áreas como: dosimetria UV-Vís, materiais para baterias e armazenamento de cargas e nanoestruturas organizadas. / Supramolecular chemistry is the most promising path on the development of nanotechnology. This is due to the special way that different molecules interact, exchanging information and generating organized structures. This PhD thesis intends to contribute in the supramolecular research field, with the study of three functionalized terpyridines derivates and the correlated iron(II) complexes: 4\'-(3-thienyl)-2,2\':6\',2\'\'-terpyridine, (titpy), [Fe(titpy)2]2+; 4\'-(4\'-(phenyl)- 2,2\':6\',2\'\'-terpirydine (phtpy), [Fe(phtpy)2]2+ and 4\'-(4-bromophenyl)-2,2\':6\',2\'\'- terpirydine (Br-phtpy), [Fe(Br-phtpy)2]2+. The investigations of the prepared compounds were done by spectroscopy, physicochemical and computational methods. The properties of the synthesized complexes were exploited in the supramolecular chemistry sense by the interactions of those compounds with α-cyclodextrin, vanadium pentoxide gel matrix and gold nanoparticles. The originated materials presented features that make possible the employment of them in distinct areas such: UV-Vis dosimeter, batteries and charge storage, and organized nanostructures

Nesta tese são discutidos alguns aspectos importantes no desenvolvimento de sistemas fotovoltaicos moleculares. São abordados temas de interesse como a síntese de novos sensibilizadores para células solares sensibilizadas por corante, o desenvolvimento de novos materiais fotoativos, Química Supramolecular, bem como a aplicação de sistemas fotovoltaicos em eletrônica molecular, especificamente no desenvolvimento de portas lógicas moleculares e dispositivos de memória. A porfirina TBPyP, contendo quatro ligantes 2,2\'-bipiridina ligados covalentemente aos carbonos meso do anel porfirínico, foi sintetizada. Este derivado porfirínico serviu como bloco de construção de sistemas supramoleculares. A utilização desses sistemas como sensibilizadores em células solares (células de Grätzel) é discutido. Fios moleculares derivados da TBPyP foram obtidos via coordenação com íons de metais de transição e são investigados quanto à possibilidade de utilização em eletrônica molecular. Novos sistemas fotovoltaicos multicamada, utilizando filmes de porfirina depositados por evaporação a vácuo como elementos fotoativos e filmes de V2O5 como eletrodo passivo, foram estudados quanto a sua eficiência e quanto ao seu mecanismo de funcionamento. Os filmes finos de porfirina obtidos neste estudo foram testados como elelementos fotoativos em células fotovoltaicas com diferentes configurações, além daquelas utilizando filmes de V2O5. A obtenção de filmes híbridos compostos de nanopartículas de ouro e ligantes orgânicos foi desenvolvida e sua aplicação em sistemas fotovoltaicos bem como em dispositivos de memória investigada. Novas portas lógicas moleculares foram obtidas utilizando-se o arranjo de células de Grätzel convencionais sensibilizadas por clusteres trigonais de rutênio sintetizados para este fim. Seu princípio de funcionamento é discutido, bem como a seu potencial de integração em circuitos lógicos. / In this thesis some aspects concerning the development of molecular photovoltaic systems are discussed. Themes of current interest such as the synthesis of new sensitizers for dye-sensitized solar cells, the development of new photoactive materials, and Supramolecular Chemistry are treated, as well as the application of photovoltaic systems in molecular electronics, specifically in the development of molecular logic gates and memory devices. The porphyrin TBPyP, comprised of four 2,2\'-bipyridine ligands covalently linked to the porphyrin meso carbons, was synthesized. This porphyrin derivative was used as a building block on supramolecular systems. The utilization of these supramolecular species in solar cells (Grätzel cells) is discussed. The coordination of the porphyrin TBPyP with transition metal ions gave rise to molecular wires, which are investigated about its potential use in molecular electronics. New multilayer photovoltaic systems, using thermo-evaporated porphyrin films as photoactive elements and V2O5 films as passive electrodes, had their efficiency and mechanism studied. The confection of hybrid films comprised of gold nanoparticles and organic ligands was developed and its application in photovoltaic systems, as well as in memory devices, was investigated. New molecular logic gates were realized using the a Grätzel cell in its conventional configuration, sensitized by ruthenium trigonal clusters synthesized to this end.

Ce travail visait à explorer les interactions supramoléculaires comme un outil dans les domaines de la chimie hôte-invité, les nanomatériaux et les nanotechnologies en général, afin de parvenir à des objectifs différents. D'abord, une interaction classique hôte-invité a été étudiée, au moyen d'une technique innovante telle que l'ITC, puis nous avons exploité les interactions supramoléculaires afin de maitriser la production de graphène exfolié en phase liquide, en mettant un accent particulier sur l'amélioration de la qualité et la quantité du matériau produit. Enfin, nous avons étendu l'utilisation de la chimie supramoléculaire à un dispositif réel par la fonctionnalisation des électrodes d'or avec des molécules photochromiques, ouvrant alors la voie à des dispositifs organiques multifonctionnels, pouvant être contrôlés par la lumière. / This work was aimed at exploring supramolecular interactions as a tool in the fields of host-guest chemistry, nanomaterials and in general nanotechnology, in order to achieve different goals. First, a classical host-guest interaction was studied by means of the ITC technique, then we exploited supramolecular interactions in order to harness the production of liquid-phase exfoliated graphene, with a particular focus on improving the quality and quantity of material produced. Finally, we extended the use of supramolecular chemistry to a real device by functionalization of gold electrodes with photochromic molecules, hence paving the way towards multifunctional organic devices and in prospective to graphene based light-controlled multifunctional devices.

Les propriétés des matériaux découlent en partie de leur organisation à l’échelle nano ou microscopique. Dans cette thèse, on montre qu’en contrôlant la chimie aux interfaces, des organisations très régulières peuvent être obtenus spontanément dans divers matériaux polymères.Dans une première, la chimie supramoléculaire a été utilisée pour contrôler l’organisation en masse de polymères greffés à une ou deux de leurs extrémités par la thymine (Thy) ou la 2,6-diamino-1,3,5-triazine (DAT), deux unités supramoléculaires complémentaires s’associant par liaisons hydrogène. Quelque soit la nature de la chaine polymère (PE, PDMS, PPG), les matériaux présentent des organisations lamellaires nanoscopiques très régulières lorsque l’unité terminale (Thy) et/ou la chaine (PE) cristallisent. Les contributions respectives à ces organisations de la ségrégation de phase, de la cristallisation, des liaisons supramoléculaires et des interactions secondaires ont été déterminées. Il a été montré que le confinement des chaines polymères dans les lamelles empêche la formation de chaines de grandes masses molaires. Cependant, les interactions supramoléculaires Thy/DAT permettent de former des copolymères à blocs supramoléculaires en mélangeant des chaines incompatibles fonctionnalisées par ces unités.Dans une seconde partie, nous avons montré que la texturation spontanée de films acrylates photopolymérisés à l’air est gouvernée à l’interface formulation/air par l’équilibre des cinétiques de polymérisation et d’inhibition par l’oxygène. Des morphologies microscopiques très régulières, hexagonales, lamellaires ou cacahuètes, sont obtenues en contrôlant différents paramètres expérimentaux et ce pour une large gamme d’épaisseur de film (6 µm – 2 mm). L’auto-texturation confère aux films des propriétés optiques singulières (flou, clarté) qui peuvent être modulées en ajustant les caractéristiques de la morphologie. / Materials properties very often derive from their nano or micro-scale organization. In this thesis, we evidence that controlling the chemistry at the interfaces allows obtaining spontaneously very regular organizations in various polymer materials.In the first part, supramolecular chemistry has been used to control the organization in the bulk of polymer grafted at one or both extremities by thymine (Thy) or 2,6-diamino-1,3,5-triazine (DAT), two self-complementary supramolecular units interacting via hydrogen bonds. Whatever the polymer nature (PE, PDMS, PPG), materials present very regular nanoscale long-range ordered lamellar organizations if the end group crystallize (Thy) and/or the chain crystallize (PE). Respective contributions to these organizations of phase segregation, crystallization, supramolecular interactions and secondary interactions have been determined. It was shown that the confinement of chains in lamellae prevent the formation of high molecular weight chains, resulting in poor mechanical properties. However, Thy/DAT interactions allow creating supramolecular block copolymers by mixing incompatible chains functionalized with these units.In the second part, we have studied the spontaneous formation of patterns at the film surface of acrylate film during their photopolymerization under air. This phenomenon occurs if there is a balance at the film surface between the polymerization and the oxygen inhibition rates. Very regular microscale patterns (hexagons, lamellae, peanuts) have been generated by controlling some experimental parameters (UV intensity, initiator concentration) for a wide range of film thicknesses (6 µm – 2 mm). Self-patterning gives interesting optical properties to the films (haze, clarity) which can be modulated by adjusting the patterns wavelength and amplitude.

Les foldamères d’oligoquinoline carboxamide forment des structures hélicoïdales en solution et dans le solide. Ces structures sont stabilisées par liaisons hydrogène, empilement aromatique et interactions électrostatiques. Dans une première partie de ce manuscrit, les fonctions amide connectant les unités quinolines ont été substituées par des fonctions vinylène, isostères de celles-ci. Ces composés quinolynènes-vinylènes, seuls, forment principalement des structures étendues en solution. Toutefois lorsque ces nouvelles unités sont en faible proportion au sein de l’oligomères contenant principalement de connections amides, des architectures hélicoïdales ont pu être obtenues. Dans une seconde partie, des ions Cu (II) ont été introduits au centre des hélices d’oligoquinoline carboxamide. Ces ions sont liés aux atomes d’azote des quinolines, et à ceux des fonctions amides après leur déprotonation. Une organisation linéaire de ces ions a été observée dans le solide. L’auto-assemblage d’hélices, en faisceaux, par empilement aromatique d’unités acridines portées par les chaines latérales a été entrepris dans une troisième partie de ce manuscrit. De faibles associations ont pu être mises en évidence en solution. Dans le solide ces interactions, bien que faibles, ont permis le contrôle de l’organisation des hélices dans le cristal. Dans une dernière partie de ce manuscrit, la coordination de métaux a été utilisée afin de permettre l’assemblage d’hélices d’oligoquinoline carboxamide. Des ligands acridine et pyridine ont été fixés sur la périphérie de l’hélice de façon à permettre la coordination par des métaux de transition tel que le palladium (II). Ces assemblages d’hélices induits par le palladium, ont été caractérisés par RMN en solution et par diffraction des rayons X dans le solide. / Oligo-quinolinecarboxamide foldamers form stable helical structures in solution and in the solid state. These helices are stabilized by hydrogen bonds, π-π stacking and electrostatic interactions. In a first part of this manuscript, vinyl functions have been introduced as isosteres of amides. The resulting quinolylene-vinylene oligomers form mainly extended structures in solution. Helical folded conformations can nevertheless be stabilized by attaching two segments of oligoamides at both ends of an oligoquinolylene-vinylene. In a second part, copper (II) ions have been loaded into the single helices of quinolinecarboxamide foldamers. The copper (II) ions coordinate the nitrogen atoms of the quinoline units and also deprotonated amide nitrogen atoms. A one dimensional alignment of the copper (II) ions was observed in the solid state. In a third part, acridine functionalized foldamers were prepared in order to test their self-assembly into bundles through interactions between aromatic functions at the exterior of helices. Associations of the acridine functionalized oligoamides are weak in organic solution. In contrast, in the solid state, interactions between helices are mainly governed by acridine units. In a fourth part, metal coordination has been used to promote helix-helix assembly of quinoline oligoamides foldamers. Acridine and pyridine rings have been attached on the side chains of these oligomers to allow coordination with metals, palladium (II) in this case. The helix-helix assembly of quinoline oligoamides by palladium coordination has been confirmed by NMR and x-ray diffraction.

In the past 30 years, the discovery of capabilities of nucleic acids far beyond their well-known information-bearing capacity has profoundly influenced our understanding of these polymers. The discovery by the Cech and Altman labs that nucleic acids could perform catalytic functions, coupled with the Gold and Szostak groups’ demonstration of the de novo evolution of nucleic acids that bind arbitrary ligands, has resulted in a proliferation of newfound roles for these molecules. Nucleic acids have found utility in both engineered systems, such as aptamer therapeutics, as well as in newly appreciated roles in extant organisms, such as riboswitches. As a result of these discoveries, many have pondered the potential importance of the dual (catalytic and informational) roles of nucleic acids in early evolution. A high-yielding synthetic route for the nonenzymatic polymerization of nucleic acids, based on the aqueous self-assembly of their components, would provide a powerful tool in nucleic acid chemistry, with potential utility in prebiotic and contemporary nucleic acid systems alike – however, such a route remains elusive. In this thesis, I describe several steps towards such a synthetic route. In these systems, a nucleic-acid binding ligand drives the assembly of short DNA and RNA duplexes, promoting the production of long nucleic acid polymers, while suppressing the production of short, cyclic species. Additionally, the use of a reversible covalent linkage allows for the production of long polymers, as well as the incorporation of previously cyclized products into these polymers. I also report several explorations of novel base pairings, nucleic acid-ligand interactions, and nucleic acid-ion interactions that have informed our studies of self-assembling nucleic acid systems.

This thesis deals with the investigation of the first hyperpolarizabilities (β) of a large number of molecules linked to other molecules either covalently or noncovalently. Chapter 1 gives a brief introduction to supramolecular chemistry and Nonlinear Optics (NLO). A survey of literature pertinent to noncovalently interacting supramolecular assembly and their NLO properties as well as NLO properties of oligomeric systems has been presented. The scope of the present investigation has been described at the end of the chapter. Chapter 2 discusses all the methods used in carrying out this thesis work. The first hyperpolarizabilities (β) of all the compounds have been measured by the hyper Rayleigh scattering (HRS) technique; the experimental details of which are written in this chapter. Various spectroscopic techniques such as NMR, IR, UV-Vis, etc. that were used in the investigation have been presented. The subsequent chapters 3-5 deal with the actual results obtained in this work. In chapter 3 first hyperpolarizabilities of o-, m-, and p-aminobenzoic acids and their oligomers viz., dimer, trimer and tetramer (covalently linked) have been studied. The compounds are synthesized and characterized by various spectroscopic methods and their β values have been measured by HRS. The hyperpolarizability increases in going from the monomer to the dimer but decreases subsequently from the dimer to the trimer to the tetramer. This unexpected trend in β has been attributed to the formation of molecular aggregates in the trimers and tetramers. Further evidences of aggregation come from the results of1H NMR spectroscopy and conductivity measurements. In chapter 4, synthesis, characterization and HRS investigation to probe the formation, dissociation and binding constants of hydrogen bonded supramolecular complexes (noncovalent interaction) formed in solution between 6-amino-2-(pivaloylamino)pyridine and ferrocene functionalized barbituric acid and 5-methoxy-N,N′-bis(6-amino-2-pyridinyl)-1,3-benzenedicarboxamide and ferrocenyl barbituric acid have been described. From the HRS data the stoichiometry of the supramolecular complexes has been determined and compared to that from the NMR data. Some of the complex stoichiometries that are measured by HRS have not been seen in the NMR data and vice versa. The results have been rationalized in terms of the strengths and weaknesses of various spectroscopic methods as applied to this problem. Many fold increase in the β value has been realized in the supramolecular complex formation process. Depolarized HRS experiments have been carried out to obtain structural information on the complexes. In the last chapter the synthesis, characterization and measurements on the first hyperpolarizabilities of unsubstituted tetraphenylporphyrin and its metallated complexes have been presented. Synthesis of supramolecular complexes of ferrocenyl barbituric acid with functionalized porphyrin compounds has been carried out although the amount of the final complex was insufficient for HRS measurements. This chapter ends with a perspective for the future work in the direction.

Cyclodextrins (CD) are cyclic oligosaccharides composed of six to more than sixty glucose units. Large-ring cyclodextrins (LR-CD) are novel CD comprised of more than eight glucose units with cavity structures and sizes different from that of commercially available CD₆ – CD₈. LR-CD may offer unique molecular recognition properties and can be produced biocatalytically from starch using cyclodextrin glucanotransferase (CGTase, E.C. 2.4.1.19) in a short reaction time. LR-CD were isolated from glucose, CD₆ – CD₈ and other compounds by complexation of CD₆ – CD₈ as well as precipitation techniques. The yield of LR-CD (degree of polymerization from 9 to 21) was optimized using central composite design. Addition of polar organic solvents to the synthesis resulted in higher yields of LR-CD. LR-CD composed of 9 to 21 glucose units were successfully separated using reversed-phase of ODS-AQ chromatography and normal-phase of polyamine II chromatography. Maintaining optimized reaction conditions aided in a high yield of CD₉; it could be separated with reasonable yield using a single step of polyamine II chromatography. A co-grinding method helped to obtain higher solubilization levels of glibenclamide, vitamin A acetate and vitamin D₃ in CD₁₃, CD₁₀ and CD₁₁, respectively when compared to other CD. Vitamin K₁ was solubilized in distilled water with CD₆ – CD₁₃ using a co-precipitation method. When compared with other CD, CD₉ was seen to be the best solubilizer. The analysis of complexes using ESI MS showed spironolactone and glibenclamide complexed with CD₉ and CD₁₃, respectively.