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Die metallfreie Aktivierung des Treibhasgases SF6 unter Verwendung von elektronenreichen N-heterocyclischen Carbenen (NHCs) resultierte in der Bildung des jeweiligen 2,2- Difluorimidazolins und Imidazolin-2-thions bzw. 2,2-Difluorimidazolidins und Imidazolidin-2-thions. Die Reduktion der NHCs mit SF4 liefert dieselben Produkte. Im Abbau von SF5CF3 mit NHCs werden ebenfalls die zuvor genannten Produkte erhalten, wobei zusätzlich das entsprechende 2-Fluor-2-trifluormethylderivat gebildet wird. Exemplarisch wurde 1,3-Dimesityl-2,2-difluorimidazolidin [SIMes(F)2] als Fluorierungsreagenz von Aldehyden unter Bildung von Acylfluoriden sowie als Deoxyfluorierungsreagenz eingesetzt. In einem one-pot-Prozess kann zudem die Aktivierung von SF6 mit der Deoxyfluorierung von 1-Oktanol zu 1-Fluoroktan kombiniert werden. Des Weiteren konnte 1,3-Dimesityl-2-fluor-2-trifluormethylimidazolidin [SIMes(F)(CF3)] zur Trifluormethylierung von Me3SiCl und Arenen eingesetzt werden. Der Einsatz von SIMes(F)2 ermöglicht die Darstellung von des NHC-stabilisierten Al(III)- Fluorids [(SIMes)Al(F)(Me)2] durch Monofluorierung von [(SIMes)AlMe3]. Durch Variation des Fluorierungsmittels (SF4, SF6, Me3SnF) kann ein höherer Fluorierungsgrad erreicht und [(SIMes)Al(F)3] synthetisiert werden. Dieser Al-Komplex konnte durch Halogenaustausch mit Me3SiCl in [(SIMes)Al(Cl)3] überführt werden. / The metal-free activation of the greenhouse gas SF6 using electron-rich N-heterocyclic carbenes (NHCs) furnished 2,2-difluoroimidazolines or 2,2-difluoroimidazolidines and 2- thio derivatives of the NHC precursors. The NHCs can reduce SF4 as well to give same products. A complete degradation of an another greenhouse gas SF5CF3 also gave 2,2- difluoro- and 2-thio- derivatives along with the 2-fluoro-2-trifluoromethyl- derivative of the NHC precursors. The 1,3-dimesityl-2,2-difluoroimidazolidine [SIMes(F)2] was taken as an exemplary substrate to be applied in deoxyfluorination reactions and acyl fluorination of aldehydes via aldehydic C(sp2)–H bond activation. Additionally, the activation of SF6 and the fluorination of 1-octanol into 1-fluorooctane can be coupled in a one-pot process. Furthermore, trifluoromethylation of Me3SiCl and arenes was observed with the 1,3-dimesityl-2-fluoro-2- trifluoromethylimidazolidine [SIMes(F)(CF3)]. SIMes(F)2 was also used for the fluorination of complex [(SIMes)AlMe3] to synthesize the NHC stabilized Al(III) fluoride [(SIMes)Al(F)(Me)2]. Various alternative reaction routes have been developed to synthesize the NHC stabilized Al(III) fluorides [(SIMes)Al(F)(Me)2] and [(SIMes)Al(F)3] through the fluorination of [(SIMes)AlMe3] with SF4, SF6 and Me3SnF. The complex [(SIMes)Al(F)3] was successfully employed for a F/Cl exchange reaction by treating it with Me3SiCl to yield [(SIMes)Al(Cl)3] and Me3SiF.

The synthesis, characterisation and anion binding properties of a series of mono- and bifunctional Lewis acidic borylferrocene compounds are described within this thesis. The original parent compound FcBMes₂ (3.1), revealed a versatile route for the synthesis of such borylferrocenes and subsequently the analogous compound Fc*BMes₂ (3.2) was synthesised. The anion binding properties of (3.1) and (3.2) were investigated and both were shown to bind one equivalent of cyanide. The binding event was signalled by an electrochemical shift (ca. -560 mV) and a quenching of bands at 510 or 542 nm respectively in the UV/Vis spectrum, while the mode of anion binding in the solid state was established by X-ray crystallography for [ⁿBu₄N]⁺[(3.1)·CN]⁻. Incorporation of a suitable redox active dye (i.e. tetrazolium violet for 3.2) allowed conversion of the electrochemical response to a colorimetric change on cyanide binding. However, a competing response for fluoride is also seen for (3.1) and (3.2). Thus a two component system is reported involving (3.2) and the boronic ester FcB(OR)₂ (3.4), [where (OR)₂ = OCH(Ph)CH(Ph)O], which from previous research is known to selectively bind fluoride, and allows for selective colorimetric cyanide sensing by simple Boolean AND/NOT logic. 1,4-C₆H₄(BMes₂)[B(OR)₂] (3.5), 4,4-C₁₂H₈(BMes₂)[B(OR)₂] (3.6) and 1,1′-fc(BMes2)(B(OR)2) (3.7) were synthesised as possible single molecules for discrimination between cyanide and fluoride. (3.5) and (3.6) proved only capable of binding one equivalent of either anion, (3.7) showed some ability to bind two equivalents of fluoride however based on ESI-MS studies although only in the presence of a large excess of anion. Systematic variation of the para-boryl substituent was investigated by synthesis of compounds FcB(Xyl^F)₂ (4.1), FcB(Xyl)₂ (4.2) and FcB(Xyl^OMe)₂ (4.3). Anion binding studies reveal a linear increase in fluoride binding affinity consistent with that expected based on the para,/em>-Hammett parameters, however with only minor differences, while no pattern is observed with respect to their cyanide binding capabilities. The addition of neutral and cationic peripheral substituents has been investigated through synthesis of [1,2-fc(CH₂NMe₂)BMes₂] (4.6) and [1,2-fc(CH₂NMe₃)BMes₂]⁺ (4.7). Subsequent binding studies revealed (4.6) to be moisture sensitive, however reaction of (4.7) with fluoride and cyanide led to formation of the adducts [(4.7)·F]⁻ and [(4.7)·CN]⁻. The anion affinity of (4.7) exhibits a substantial increase when compared to the parent compound (3.1). Even when compared to the isomeric 1,1′ system an increase of approximately three orders of magnitude is seen attributed to the closer nature of the cationic charge and in the fluoride adduct the presence of a cooperative intramolecular hydrogen bond. The 1,1′-bifunctional analogues of the mono-substituted systems were synthesised [e.g. 1,2-fc(BMes₂)₂ (5.1)] and shown to complex two equivalents of fluoride or cyanide in acetonitrile. The 1:1 cyanide adduct of (5.1) was isolated in chloroform however, no evidence for chelation was observed. The analogous systems 1,2-fc(BMes₂)₂ (5.5), 1,2-fc(BXyl₂)2 (5.7), and 1,2-fc(BMes₂)(BXyl₂) (5.8) were also investigated. Reaction of (5.5) with fluoride and cyanide revealed it to bind only one equivalent of either anion, neither however was bound in a chelating fashion although X-ray crystallography revealed cyanide binds exo whilst fluoride binds endo to the B···B cavity. Finally the kinetics of fluoride binding were studied by UV/Vis spectroscopy and showed a systematic increase in rate constant upon reduction of steric bulk.

Cette thèse porte sur l’étude structurale de mélanges de fluorures fondus utilisés pour la production d’aluminium par électrolyse. Ce procédé est obtenu par dissolution de l'alumine (Al₂O₃) dans un bain de cryolithe fondue (NaF-AlF₃ plus quelques additifs) à 960°C. Afin d’obtenir des données d’entrée pour la modélisation électrocinétique des phénomènes de transport durant le procédé, une meilleure description de la spéciation dans les bains en fonction de leur température et de leur composition est nécessaire.Pour déterminer cette spéciation in situ, nous avons développé une démarche originale combinant la spectroscopie par Résonance Magnétique Nucléaire (RMN) à haute température avec des simulations de Dynamique Moléculaire (DM) couplés à des calculs de premiers principes. Ces derniers basés sur la théorie de la fonctionnelle de la densité (DFT) ont permis de calculer les paramètres d’interaction mis en jeu lors des expériences RMN et d’évaluer la qualité des modèles issus de la DM par comparaison avec les données expérimentales.Les mesures et simulations effectuées dans les systèmes binaires MF-AlF₃ (M= Na ou K) ont confirmé la présence d’ions F‾ et d’espèces anioniques [AlFₓ]³‾ˣ avec une durée de vie comprise entre 5 et 25 ps. La probabilité de former des dimères du type [Al₂Fm]⁶‾ᵐ est inférieure à 10 %. Quel que soit l’alcalin, l’ajout d’alumine dans ces systèmes affecte la proportion d’espèce AlF5²‾ pour former des oxyfluoroaluminates : [Al₂OF6] ²‾, [Al₂OF8]⁴‾, [Al₂O₂F4] ²‾, [Al₂O₂F6]⁴‾ et [Al₂O₃F₂]²‾. Ces derniers sont peu influencés par la présence de CaF₂. En se dissociant partiellement, celui-ci contribue à modifier les équilibres chimiques vers les milieux plus basiques et à augmenter la coordinence moyenne des ions aluminium. / This thesis deals with the structural study of molten fluorides mixtures used for aluminium production by electrolysis. This process is obtained by dissolving alumina (Al₂O₃) in a molten cryolite bath (NaF-AlF₃ plus some additives) at 960°C. In order to obtain input data for the electrokinetic modeling of transport phenomena during the process, a better description of speciation in baths as a function of their composition and temperature is required.To determine this in situ speciation, we developed an original approach combining high temperature nuclear magnetic resonance (NMR) spectroscopy with Molecular Dynamics (MD) simulations coupled with first principle calculations. Based on the density functional theory (DFT), it was possible to calculate the interaction parameters involved in NMR experiments and to evaluate the quality of the models derived from MD when compared to the experimental data.The measurements and simulations carried out in the MF-AlF₃ binary systems (M = Na or K) confirmed the presence of F- and anionic species [AlFₓ]³‾ˣ with a lifetime between 5 and 25 ps. The probability of forming dimers [Al2Fm]6-m is less than 10%. Regardless of alkali, the addition of alumina in these systems affects the proportion of AlF5²‾ species to form oxyfluoroaluminates: [Al₂OF6] ²‾, [Al₂OF8]⁴‾, [Al₂O₂F4] ²‾, [Al₂O₂F6]⁴‾ et [Al₂O₃F₂]²‾. The latter are little influenced by the presence of CaF₂. By partially dissociating, this contributes to modifying the chemical equilibria towards the more basic media and to increasing the average coordination of the aluminium ions.

Este estudo teve como objetivo avaliar do efeito da aplicação tópica de um verniz e solução experimental de TiF4, comparando-os ao verniz e solução de NaF, sobre o processo de des-remineralização do esmalte dentário in situ. Para tal, 132 blocos de esmalte bovino (4x4mm) foram selecionados pela microdureza de superfície, sendo que em metade deles foi produzida lesão de cárie artificial em solução desmineralizante (pH 5,0, 6 dias). Na seqüência, foi determinada a microdureza de superfície pós-lesão. A outra metade dos blocos permaneceu hígida. Onze voluntários participaram de 3 fases cruzadas (14 dias cada, washout de 7 dias), boca-dividida e cegas, nas quais utilizaram aparelhos palatinos com 4 amostras de esmalte por fase (2 hígidas e 2 desmineralizadas), sendo que cada tipo de amostra recebeu um tipo de tratamento (verniz ou solução). Em todas as amostras permitiu-se o acúmulo de placa dentária. Em uma fase (Fase A), foram aplicados agentes a base de NaF a 5,42% (2,45% F- e pH 5,0), em outra fase (Fase B), foram utilizados agentes a base de TiF4 a 4% (2,45% F- e pH 1,0), e na última fase (Fase C) foram utilizados agentes placebos (verniz sem flúor pH 5,0 e sem tratamento). Os tratamentos foram realizados in vitro (verniz-6 h e solução-1 minuto). Durante o período in situ, os voluntários aplicaram solução de sacarose a 20%, 8x5min ao dia, sobre os blocos hígidos, para provocar a desmineralização. Já para os blocos desmineralizados nenhum procedimento foi realizado, para permitir a remineralização. A microdureza de superfície final foi realizada, para o cálculo da porcentagem de variação de microdureza de superfície, assim como a microdureza longitudinal e microradiografia transversal, para o cálculo das perdas de microdureza e volume mineral integradas, respectivamente. Os dados foram submetidos à ANOVA-RM/ Tukey-Kramer, teste t pareado e ANOVA a dois critérios/Bonferroni (p<0,05). Houve uma redução significativa da desmineralização superficial e um aumento significativo da remineralização superficial do esmalte in situ pelos tratamentos com verniz e solução de TiF4, em comparação aos controles. Pôde-se constatar ainda que os tratamentos com o verniz de NaF, verniz de TiF4 e solução de TiF4 foram efetivos na redução da desmineralização subsuperficial in situ. No entanto, observou-se que o protocolo experimental não permitiu uma adequada remineralização de subsuperfície in situ. Com base nos resultados, pode-se concluir que o verniz e a solução de TiF4 parecem ser promissores na prevenção da desmineralização, porém em relação à remineralização mais estudos in situ são necessários. / The aim of this study was to evaluate the effect of the experimental TiF4 varnish and solution, comparing with NaF solution and varnish, on dental enamel de-remineralization in situ. For that, 132 bovine enamel samples (4x4 mm) were selected using surface microhardness, and half of them were submitted to artificial caries lesion formation using a demineralizing solution (pH 5.0, 6 days). The surface microhardness after the demineralization was measured. The other half of the samples remained sound. Eleven volunteers took part in this cross-over, split-mouth and double-blind study performed in 3 phases of each 14 days (washout of 7 days). Four enamel samples were worn in palatal appliances (2 sound and 2 demineralized), being each type of sample submitted to one treatment (varnish or solution). The dental plaque accumulation was allowed on all samples. In phase A, 5.42% NaF varnish/solution was applied (2.45% F-, pH 5.0); in phase B, 4% TiF4 varnish/solution was used (2.45% F-, pH 1.0) and at the last phase (phase C) the placebo treatments were performed (placebo varnish pH 5.0 and no-treatment). The treatments were performed in vitro (varnish-6h and solution-1min). During the in situ phase, the volunteers dripped a solution containing 20% weight/volume (w/v) sucrose on the sound samples for 5 min, 8 times a day, to provoke demineralization. While on the demineralized samples nothing was done, in order to allow remineralization. The final surface microhardness was analyzed for the calculation of the % of surface microhardness change, as well as the cross-sectional hardness and the transversal microradiography, for the calculation of the integrated loss of microhardness and mineral volume, respectively. The data were submitted to RM-ANOVA/ Tukey-Kramer, t test and 2-way ANOVA/ Bonferroni (p<0.05). There was a significant reduction of the surface enamel demineralization and increase of surface remineralization by the treatments with TiF4 varnish and solution compared to control in situ. The treatments with NaF varnish, TiF4 varnish and solution were able to reduce the subsurface demineralization in situ. However, the experimental protocol did not allow the subsurface remineralization in situ. Based on the results, it can be concluded that the TiF4 varnish and solution seem to be promising products for preventing demineralization, but for the remineralization more studies need to be conducted.

Este estudo teve como o objetivo avaliar in vitro o efeito do tratamento com vernizes de tetrafluoreto de titânio (TiF4) e fluoreto de sódio (NaF) (ambos com 0,95%, 1,95% e 2,45% F) sobre 1) a quantidade de F- liberada em água deionizada e saliva artificial, por período de 12h; 2) os tipos de compostos formados pela interação com a hidroxiapatita (neste caso, com soluções ao invés dos vernizes); 3) a porcentagem de elementos presentes na superfície do esmalte bovino e humano, hígidos (H) e desmineralizados (DES); 4) a quantidade de CaF2 sobre a superfície do esmalte bovino e humano, H e DES. Adicionalmente, 5) o efeito dos vernizes de TiF4 e NaF sobre a remineralização do esmalte bovino, em diferentes condições in situ, foi avaliado. Para etapa 1, a liberação de F- foi quantificada por eletrodo de íon específico. Na etapa 2, pó de HAP produzido por precipitação foi tratado com soluções fluoretadas. Os compostos formados foram avaliados por espectroscopia de infravermelho e difração de raios-X. Nas etapas 3 e 4, as superfícies tratadas com os vernizes foram analisadas por MEV- EDAX e por biópsias básicas, respectivamente. Vinte voluntários (n final=17) participaram do ensaio in situ com 3 fases cruzadas, os quais utilizaram aparelhos palatinos contendo amostras de esmalte bovino desmineralizadas tratadas com vernizes de TiF4, NaF ou placebo. As amostras foram submetidas a diferentes condições de des-remineralização (presença ou não de tela plástica; variação da frequência de aplicação de sacarose 20%) e à exposição ao dentifrício fluoretado. O volume mineral e profundidade da lesão foram avaliados por microradiografia transversal (TMR). 1) Os vernizes de TiF4 (1,95 e 2,45% F) liberaram mais fluoreto comparados aos vernizes de NaF tanto em água como em saliva artificial, sendo a diferença significativa nas primeiras 6h de contato (p<0,0001). 2) O TiF4 causou alteração na estrutura da HAP e induziu à formação de novos compostos como TiO2 e Ti (HPO4)2. 3) Os vernizes de TiF4 induziram à formação de uma camada de revestimento sobre a superfície do esmalte com microfissuras em sua extensão, rica em Ti e F. 4) Adicionalmente, o TiF4 (1,95 e 2,45% F) produziu maior deposição de fluoreto álcali-solúvel que o NaF, especialmente sobre o esmalte bovino em comparação ao humano. Maior deposição de fluoreto foi vista também para o esmalte DES em comparação ao H (p<0,0001). 5) O verniz de TiF4 (2,45% F) aumentou significativamente a remineralização de lesões artificiais de cárie em relação ao NaF, independente da severidade do desafio cariogênico in situ. Já o efeito remineralizante do NaF foi dependente da condição cariogênica (p<0,0001). Portanto, o verniz de TiF4 é promissor na remineralização de lesões iniciais de cárie dentária, sendo este efeito relacionado à formação de uma camada superficial protetora rica em compostos à base de Ti e à maior deposição de fluoreto no esmalte. / This study aimed to evaluate the in vitro effect of titanium tetrafluoride (TiF4) and sodium fluoride (NaF) varnishes (both with 0.95%, 1.95%, 2.45% F) treatment on the 1) F- release in deionized water and artificial saliva for 12h period; 2) types of compounds formed by the interaction with hydroxyapatite (in this case, solutions were tested instead of varnishes); 3) percentage of the elements on bovine and human, sound (S) and demineralized (DE), enamel surface; 4) F- uptake (CaF2 deposition) on human and bovine, S and DE, enamel surface. Additionally, 5) the effect of TiF4 and NaF varnishes on bovine enamel remineralization, in different in situ conditions, was assessed. In study 1, the F- release was measured by ion specific electrode. In study 2, HAP powder, produced by precipitation, was treated with fluoride solutions. The compounds formed were evaluated by infrared spectroscopy and X-ray diffraction. In studies 3 and 4, the surfaces treated with the varnishes were analyzed by SEM-EDAX and basic biopsies, respectively. Twenty volunteers (final n=17) participated of the in situ study with 3 crossover phases, in which they wore palatal appliances containing bovine demineralized enamel samples treated with TiF4, NaF or placebo varnishes. The samples were subjected to different de-remineralization conditions (presence or absence of plastic mesh and variation in frequency of application of 20% sucrose) and exposure to fluoride dentifrice. Themineral content and lesion depth were evaluated by transverse microradiography (TMR). 1) The TiF4 varnishes (1.95 and 2.45% F) released more F- compared to NaF varnishes in both water and artificial saliva, and significant difference was found in the first 6h (p<0.0001). 2) The TiF4 caused change in the HAP structure and induced the formation of new compounds such as TiO2 and Ti (HPO4)2. 3) The TiF4 varnishes induced the formation of a coating layer rich in Ti and F, with microcracks in its extension, on the enamel surface. Additionally, TiF4 (1.95 and 2.45% F) provided higher deposition of alkali-soluble Fluoride than NaF, especially on bovine enamel compared to human enamel. 4) Higher fluoride diposition was also seen on DE compared to S enamel (p<0.0001). 5) The TiF4 varnish (2.45% F) significantly increased the remineralization of artificial carious lesions compared to NaF, regardless of the severity of cariogenic challenge in situ. On the other hand, the remineralizing effect of NaF was dependent on the cariogenic condition (p<0.0001). Therefore, the TiF4 varnish is promising agent in the remineralization of incipient dental caries lesions, whose effect is related to the formation of a protective surface layer rich in Ti compounds and to the increase in fluoride deposition on the tooth enamel.