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About half a century ago, Főrster and Kasper discovered that traditional organic chromophore such as pyrene was weakened with an increase in its solution concentration. It was soon recognized that this was a general phenomenon for many aromatic compounds. This concentration-quenching effect was found to be caused by the formation of sandwich-shaped (disc-like) excimers and exciplexes aided by the collisional interactions between the aromatic molecules in the excited and ground states. In 2001, Tang¡¦group discovered such a system, in which luminogen aggregation played a constructive, instead of a destructive, role in the light-emitting process: a series of silole molecules were found to be non-luminescent in the solution state but emissive in the aggregated state. They coined the term ¡¥¡¥aggregation-induced emission¡¦¡¦ (AIE) or ¡§AIE enhancement¡¨ (AIEE) for this novel phenomenon which originated from the restricted intramolecular rotation (RIR) inherent from the chemical structures of the luminescent materials. To verify the effect of molecular structure on the AIE properties of organic and polymeric materials, four approaches were attempted in this research. (I) Aggregation-Induced Emission in Tetraphenylthiophene-Derived Organic Molecules and Vinyl Polymer Organic molecules of tetraphenylthiophene (TP) and the derived model compound of TP-Qu and vinyl polymer of PS-Qu with the pendant group of TP-Qu were prepared and characterized to identify their photoluminescent responses toward the effect of AIE. During aggregate formation, the corresponding TP solutions greatly gained the emission intensity. In contrast, TP-Qu and PS-Qu in isolated or aggregated states emitted strongly with nearly the same emission intensity. RIR is the key factor deciding the AIE effect in different states. With four small phenyl rotors around the central thiophene stator, the RIR of the TP molecules in dilute solution is low but increases upon aggregate formations. In contrast, the bulky C-2 quinoline rotor of the TP-Qu molecule enhances the RIR in isolated state. With the inherent TP-Qu pendant groups, the emissive behavior of vinyl polymer PS-Qu is similar to the TP-Qu molecule. (II) Aggregation-Induced Emission Enhancement of Diblock Copolymer Containing Tetraphenylthiophene-Quinoline Pendant Fluorphores by Selective Solvent Pairs In this study, diblock copolymer of PSQu-PBS containing 25 mol% of fluorescent PSQu segments was synthesized and its aggregation-induced emission enhancement (AIEE) behavior was characterized and compared to PSQu homopolymer with 100 mol% of fluorescent units. With fewer (25 %) fluorescent units, solutions of diblock PSQu-PBS copolymer actually have higher (or comparable) emission intensities than the homopolymer PSQu solutions. Solutions of PSQu-PBS in THF/H2O of varied compositions emit essentially with the same intensity but in contrast, emissions of PSQu-PBS in THF/hexane increase with the increasing hexane content. Copolymer micelles formed in THF/hexane mixtures are supposed to have higher extent of aggregation, leading to more pronounced AIEE effect than micelles formed in THF/H2O. (III) Tetraphenylthiophene-Functionalized Poly(N-isopropylacrylamide): Probing LCST with Aggregation-Induced Emission A hydrophobic TP center with novel AIE property was chemically linked to two poly(N-isopropylacrylamide) (PNIPAM) chains to obtain thermoresponsive polymers to study the relationships between the lower critical solution transitions (LCSTs) and the AIE-operative fluorenscence emission. Three ethynyl-terminated PNIPAMs with different molecular weights were synthesized via controlled atom transfer radical polymerization (ATRP) using ethynyl-functionalized initiator. The PNIPAMs were then coupled with diazide-funtionalized TP (TPN3) via click reaction to obtain the desired TP-embedded polymers of Px (x = 1, 2, and 3). All three polymers show AIE-property from their solution fluorescence behavior in THF/hexane mixtures. In the aqueous solution, the TP-center served as a fluorogenic probe that reveals the LCSTs of polymers and its relation to the degree of TP labeling in terms of polymer concentration. The thermoresponsiveness of Px was demonstrated by the complete emission quench when heated at temperatures above LCST. Dissociation of the TP aggregates above LCST is responsible for the emission quench. (IV) Influence of Molecular Weight on the Aggregation-Induced Emission of Vinyl Polymers Containing the Fluorescent 2,4,6-Triphenylpyridine Pendant Groups Molecular weight effect on the AIEE property of vinyl polymers containing fluorescent 2,4,6-triphenylpyridine (TPP) pendant groups was evaluated in the fourth topic. The high and low Mw vinyl polymers of PDMPS¡VL and ¡VH were prepared through Click chemistry between azide¡VTPP derivative and acetylene¡Vfunctionalized polystyrenes. Solutions of the low Mw PDMPS¡VL exhibited the normal AIEE effect with continuous emission gains with increasing extent of aggregation upon nonsolvent inclusion. On the contrast, the high Mw PDMPS¡VH solutions emitted with constant intensity on all solutions with different extent of aggregation. Despite the varied solution behavior, the solid PDMPS-L and ¡VH films are all strong deep-blue emitter with high quantum yields of 84 and 82.5%, respectively. The emission behavior was explained by the conformational difference between the PDMPS¡VL and ¡VH chains, which were approached by computer simulation in this topic.

In this study, tetraphenylthiophenen (TP) with aggregation-induced emission enhancement (AIEE) property is served as terminal and central fluorophores of poly(£^-benzyl-L-glutamate) (PBLG)-based polymers of TP1PBLG and TP2PBLG, respectively, to probe for the relationship between the secondary structure (£\-helix) of polypeptides and the ALEE-operative fluorescence (FL). Intermolecular aggregation of the central TP unit in the di-substituted TP2PBLG is sterically blocked by the large £\-helical PBLG chains, which lead to the reduced AIEE-oriented FL. On the contrast, the terminal TP units in TP1PBLG can easily approach each other to form aggregates with strong FL. Factor (e.g. solvent annealing) controlling the fraction of £\-helix chain also varies the corresponding emission intensity. Conformational difference between TP1PBLG and TP2PBLG evaluated from the infrared and the X-ray (wide- and small-angle) diffraction spectra is also used to verify its influence on the AIEE-operative FL behavior.

Les recherches sur le photovoltaïque organique depuis une dizaine d’année ont permis une constante progression de l’efficacité des cellules solaires. Plusieurs groupes de recherche ont amorcé une réflexion sur les procédés de synthèse qui permettraient de limiter les déchets. Ainsi le couplage par arylation directe qui évite l’utilisation de dérivés organométalliques a émergé comme alternative au couplage organométallique classique. Une première partie est consacrée à l’étude méthodologique du couplage par arylation directe de la triphénylamine avec des dérivés du thiophène-2- carboxaldéhyde substitués en C3 et C4 par des groupements électro-accepteurs et électro-donneurs. Ce motif de base permet l’accès à trois séries de petites molécules par simple condensation. Des cellules photovoltaïques atteignant des rendements de photo-conversion de 3% en cellules bicouches, ont été obtenues. Dans une deuxième partie, la polymérisation par arylation directe sur des monomères du thiophène substitué par des groupements nitriles comme accepteur et des groupements alcoxy ou thioalkyl comme donneur conduit en une seule étape à une nouvelle famille de polymères conjugués. Ces polymères ont été utilisés comme matériaux donneurs et accepteur dans des cellules. Enfin en dernière partie, un travail exploratoire sur les propriétés d’émission de dérivés du benzofurane a été entrepris. Des réactions de condensation de Knoevenagel ont été développées pour obtenir toute une série de dérivés contenant l’unité cyano-vinylbenzofurane. La plupart des composés présente une forte émission à l’état solide. / Research on organic photovoltaics over a decade allowed a steadily increasing in the efficiency of solar cells. Several research groups have begun a reflection on the synthesis processes to limit wastes. Thus the direct arylation coupling which avoids the use of organometallic compounds, has emerged as an example of green reaction. The first part is devoted to the methodological study of direct arylation of bromotriphenylamine with thiophene-2-carboxaldehyde derivatives substituted in C3 and C4 by electron-withdrawing groups and electron-donor groups. This basic pattern allows access to three small molecules by condensation. Photovoltaic cells reaching photoconversion efficiencies of 3% were obtained. In the second part, the polymerization by direct arylation of sustituted thiophene monomers by nitrile groups as the acceptor and by alkoxy or thioalkyl as the donor led in one step to a novel family of conjugated polymers having donor and acceptor groups alternately. Solar cells were made with the polymers as donors or as acceptors materials. Finally, in the last part, exploratory work on the emission properties of benzofuran derivatives have been made. Knoevenagel condensations have been developed for a range of compounds containing the cyano-vinylbenzofuran unit. Most compounds have high emission in the solid state.

In this study, organic and polymeric fluorophores based on 2,4,6-triphenylpyridiene (TPP) structure were found to have the novel aggregation-induced emission enhancement (AIEE) property. For the small-mass fluorophores, TPP and cyano-functionalized TPP (TPP-CN) were prepared from the facile Chichibabin reaction and their AIEE properties were characterized by the emission behavior in solvent/nonsolvent pair. Solid samples of TPP and TPP-CN exhibit enhanced emission with increasing annealing time under solvent vapors, thus, both compounds have the characters of crystallization-induced emission enhancement (CIEE) behavior. For polymeric system, copolymers PTPPF containing alternative TPP and 9,9-dioctylfluorene units were prepared through Suzuki coupling and study on its fluorescence behavior also reveals its AIEE feature. The rigid polymer possesses high emission intensity in its dilute solution state and remains almost unchanged with increasing nonsolvent fraction. The solid sample was found to have a high quantum yield (ФF) of 70 %.

The work centersaround perfluoroaryl azides (PFAAs), and theirability to undergo certain fast and robusttransformations. The chemistry was furtherappliedfor biomedical applications. The first section focuses on the azide-aldehyde-amine cycloaddition using PFAAs. Experimental and computational investigations uncovered a fast azide-enamine cycloaddition to form triazolines, which spontaneously rearrange into stable amidine products. In addition, this transformation was explored in the formulation of pure nanodrugs. Because this reaction can introduce a phenyl and a perfluoroaryl moiety enabling supramolecular interactions near the antibiotic drug, the resulting ciprofloxacin derivatives formed nano-sized aggregates by precipitation, which displayed aggregation-induced emission for bacterial imaging as well as enhanced size-dependent antibacterial efficacy. In the second section, the high electrophilicity of PFAAs was explored to transform azides to aryl amides. The reactivity of PFAAs in the thioacid/azide reaction was studied. In addition, PFAAs were discovered to react with phenylacetaldehyde to form aryl amidesviaan azide-enol cycloaddition, similar tothe perfluoroaryl azide-aldehyde-amine reaction.This strategyof amide synthesiswas furthermoregeneralized through a combination of base-catalyzed azide-enolate cycloaddition reaction and acid-or heat-promoted rearrangement of triazolines. The last section describes a type of azide fluorogens whose fluorescence can be switched on by alight-initiated intramolecular nitrene insertion intoa C-H bond in the neighboring aromaticring. These fluorogenic structures were efficiently accessed via the direct nucleophilic aromatic substitution of PFAAs. / <p>QC 20150903</p>

[pt] Derivados do núcleo 2,1,3-benzotiadiazola (BTD) são altamente emissivos e têm reconhecida aplicação em diversas áreas da tecnologia da luz (células solares sensibilizadas por corantes, sondas fluorescentes, dispositivos emissores tipo OLEDs, etc). Derivados de BTD substituídos com grupos estireno têm sido descritos como ótimas sondas fluorescentes para estudo de conformações de proteínas. Além disso, o grupo de pesquisa do LaSOQF tem produzido novos derivados de BTD luminescentes e buscado diferentes aplicações para os mesmos. Assim sendo, o objetivo desse trabalho foi desenvolver/otimizar a síntese de novos derivados de BTD estiril-substituídos. Nesse planejamento almejou a obtenção de compostos com intensa luminescência a partir da substituição de um grupo estiril por grupos 4-metóxifenil, 4-metoxifenóxi ou 2-bifenil, buscando acentuar o caráter de transferência de carga intramolecular (ICT) e, também, características de emissão aumentada induzida por agregação (AIEE). Para a obtenção dos compostos desejados, os derivados bromados de BTD foram submetidos a reações de Heck com o estireno. Dessa forma, as moléculas alvo foram obtidas com rendimentos entre 36 por cento e 87 por certo. Em seguida, a caracterização fotofísica dos fluoróforos foi realizada e foram obtidos máximos de absorção entre 404 e 450 nm e máximos de emissão entre 503 e 578 nm, indicando a alta estabilidade do estado excitado (delta lambda igual 90-121 nm). Os valores determinados de [fi]FL (0,31-0,69) confirmaram a alta emissividade dos compostos. Ademais, o composto 4-(4-metoxifenóxi)-7-estirilbenzo[c][1,2,5]tiadiazola apresentou características de AIEE. As novas moléculas desenvolvidas estão sendo aplicadas como sondas fluorescentes para a determinação de água em soluções etanólicas comerciais. / [en] The 2,1,3-benzothiadiazole (BTD) core derivatives are highly emissive and with recognized application in several areas of light technology (dye-sensitized solar cells, fluorescent probes, emitters devices such as OLEDs, etc.). BTD derivatives substituted with styrene group have been described as excellent fluorescent probes for protein conformations study. In addition, the LaSOQF research group has been producing new luminescent BTD derivatives and proposed different applications for them. Therefore, the objective of this work was to develop/optimize the synthesis of novel styryl-BTD derivatives. This design aimed at obtaining more luminescent compounds from the replacement of one of the styryl groups by 4-methoxyphenyl, 4-methoxyphenoxy or 2-biphenyl, seeking for intramolecular charge transfer (ICT) and also aggregated-induced enhanced emission (AIEE) characteristics. To obtain the desired compounds, brominated BTD derivatives were submitted to Heck reactions with styrene. Thus, the target fluorophores were obtained with yields ranging between 36 per cent and 87 per cent. Then, photophysical characterization of the fluorophores was carried out and absorption maxima between 404 and 450 nm and emission maxima between 503 and 578 nm were obtained, indicating the high stability of the excited state (delta lambda equal 90-121 nm). The determined values of [fi]FL (0.31-0.69) confirmed the high emissivity of the compounds. In addition, the compound 4-(4-methoxyphenoxy)-7-styrylbenzo[c] [1,2,5]thiadiazole showed of AIEE properties. The novel molecules developed are being applied as fluorescent probes for determination of water in commercial ethanolic solutions.

In the last few years, considerable efforts have been given to develop sensitive and effective sensors for explosive materials and to generate systems which exhibit high luminescence in both solution and solid-state. The increasing number of terrorist activities around the world have prompted scientists to design effective ways to detect and disarm even the trace amount of explosives. The nitroaromatics (NACs) are the common constituents of most of the explosives due to high explosive velocity and ease of availability. The NACs were extensively used as the main constituents in landmines until World War II. Apart from their explosive behavior, the NACs are well-known environmental pollutants. The industrial waste and the leakages from unexploded landmines are the major contributors towards the soil and ground water contamination. Presently for effective detection of trace amount of explosives, skilled canines and metal based detectors are commonly used. The canines are trained for a specific type of explosives which limit their ability to detect different types of substrates. The chemical sensors that work on the principle of colorimetric and/or fluorimetric detection techniques have emerged as suitable alternative due to cheap production cost, portability and sensitivity. Different types of materials including conjugated polymers, metal-organic frameworks (MOFs), and quantum-dots have been reported as efficient chemosensors for NACs. However, poor solubility in the common organic solvents, low solid-state fluorescence, very high molecular weight and lack of signal amplification have restricted the application of these material for in-field testing. Renewed interests have been invested in small molecule based systems; and metal-organic discrete molecular architectures due to precise control over their photophysical properties and the supramolecular interaction among neighboring molecules that facilitates energy migration among the molecular backbone. On the other hand, recently post-synthetic modification of different molecular systems including MOFs and polymers has emerged as a potential technique to incorporate desired functional groups into the system and to tune their properties with the retention of basic structures. Reports on the post-synthetic modification of discrete metal-organic architectures are rare due to the delicate nature of the metal-organic bonds that ruptures on mild environmental changes. Therefore, post-synthetic functionalization of discrete molecular systems using mild reaction conditions will open up a myriad of possibilities to generate new systems with desired characteristics. Chapter 1 of the thesis will briefly discuss the history of different explosive materials including different detection methodologies that are widely used. It will also include a brief discussion on different small molecular systems with high solid-state luminescence. In Chapter 2, design and synthesis of triphenylamine-based two Platinum(Pt)(II) molecules functionalized with carboxylic acid and ester groups including their organic analogues have been discussed. The triphenylamine core was chosen due its unique non-planarity and luminescence. On the other hand, Pt(II) center was incorporated to increase intermolecular spacing in solid-state that can induce high luminescence. Scheme 1. Schematic representation of fluorescence quenching using small molecules. All the four molecules were found to be highly sensitive towards NACs including picric acid and dinitrophenol. Although the molecules exhibited similar sensitivity in solution, the carboxylic acid analogues demonstrated superior sensitivity in solid-state. Careful observation of the crystal structures of the systems revealed the acid analogues were oriented in a 2-D grid-like pattern that facilitated energy migration among neighboring molecules (Scheme 1.). Chapter 3 describes design, synthesis, and NACs sensing behavior of anthracene-based four purely organic small molecules. The molecules exhibited high selectivity towards picric acid only. All the molecules were found to be highly emissive in both solution and solid-state due to the vinylanthracene backbone (Scheme 2.). Scheme 2. Schematic representation of fluorescence quenching and solid-state sensing behavior. Chapter 4 discusses the strategy to develop mechano-fluorochromic and AIE active triphenylamine-based Pt(II) complex and its organic analogue. The twisted triphenylamine backbone restricted molecular close packing in solid-state; and weak C-H-- interactions were utilized to hinder the motion of the phenyl rings. As a result, the molecules were highly emissive in solid-state. Grinding disrupted the intermolecular interactions and thus mechano-fluorochromic behavior was observed. Due to twisted backbone, the molecules were also found to be AIE active. Both the systems containing terminal aldehyde groups were finally utilized for selective detection of biomolecule cysteine (Scheme 3.). Scheme 3. Mechano-fluorochromic and AIE behavior of the triphenylamine based Pt(II) complex. In Chapter 5 vinylanthracene-based linear donor was used in combination with carbazole-based 90° and triphenylamine-based 120° Pt(II) acceptors to generate (4+4) and (6+6) molecular squares and hexagons, respectively. The vinylanthracene backbone imparts high solution and solid-state luminescence to the system as well as made them AIE active. The molecules were further investigated for the solution and solid-state sensing for NACs and found to be effective for trinitrotoluene (TNT) and dinitrotoluene (DNT) (Scheme 4.). Scheme 4. Schematic representation of AIE active molecular square and its NACs sensing. Chapter 6 describes the formation of Pd3 self-assembled molecular trinuclear barrels containing triphenylamine imidazole donors and Pd(II) acceptors. Using Knoevenagel condensation the aldehyde group present in the barrel was post-synthetically functionalized with Meldrum’s acid. From spectroscopic characterization, it was proved that the structural integrity remained intact after the post-modification treatment (Scheme 6.). Surprisingly, pre-synthetic modification of the donor alone with Meldrum’s acid followed by self-assembly treatment with the Pd(II) ion did not yield trigonal barrel 6.8. Scheme 6. Post-synthetic functionalization of trinuclear barrels using Knoevenagel condensation.(For colour pictures pl see the abstract pdf file)

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