M.Tech (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Dithiocarbamate ligands and their complexes has been a subject of interest in various fields but they found much interest in medical applications as potential anti-microbial agents. The dithiocarbamate ligands were used to prepare complexes of copper and zinc. All the prepared ligands and complexes were characterized using techniques such as IR and 13CNMR spectroscopy and thermogravimetric analysis (complexes). The data obtained from the spectroscopies was consistent with the coordination of the ligand to the metal ion through the sulfur atoms of the dithiocarbamate or thioureide moiety. The thermal analysis of the prepared complexes gave a final residue of metal sulfide, thus indicating the potential of the prepared complexes as single molecular precursor for the synthesis of metal sulfide nanoparticles. The prepared complexes were then used to synthesize metal sulfide nanoparticles. The nanoparticles were successfully prepared by thermal decomposition of a single-source precursor (dithiocarbamate complexes) in a solution of hexadecylamine (HDA) or tri-n-octylphosphine oxide (TOPO). The investigated parameters were the capping molecule (HDA and TOPO), and capping molecule concentration (3 g and 6 g) to see their effect on the shape and size of the synthesized nanomaterials. The synthesized metal sulfide nanoparticles were characterized using techniques such as UV-vis spectroscopy, photoluminescence spectroscopy, X-ray diffraction analysis and transmission electron microscopy. The absorption study showed some interesting features in the prepared nanomaterials. The first was the red-shifted spectra of the ZnS nanoparticles which was attributed to the impurities and that assumption was further confirmed by the XRD analysis that showed a sulfur impurity and other amorphous peaks. The second was the localized surface plasmon resonances on the copper sulfide nanoparticles that suggested the formation of electron deficient copper sulfide stoichiometry that was further confirmed by XRD analysis that gave hexagonal phase copper sulfide covellite. The TEM images of the prepared nanoparticles showed that the concentration and the capping molecule has an effect on the size and shape of the synthesized nanoparticles. The increase in capping concentration gave a decrease in particle size in most of the prepared nanoparticles, while they were few exceptions. The capping molecule effect showed that most of the nanoparticles prepared from TOPO were spherical in shape and were well dispersed compared to the mixed morphological nanoparticles prepared from HDA. There were also exceptions of the well dispersed HDA-capped nanoparticles.

Devido à sua baixa solubilidade em água, os pirrolidinoditiocarbamatos poderiam produzir eletrodos livres do problema de lixiviação do modificador, os quais poderiam ser usados como detectores amperométricos, em análises em fluxo e outros procedimentos hidrodinâmicos. O complexo poderia agir como um intermediário de transferência de elétrons entre o analito e a superfície eletródica, aumentando a sensibilidade da resposta analítica do sensor. Desta forma, eletrodos de pasta de carbono modificados (EPCM) com complexos de pirrolidinoditiocarbamatos anidros de diversos metais foram preparados e testados quanto à sua aplicação em técnicas voltamétricas. Os complexos de manganês(II), [MnPyr2] e cobalto(II), [CoPyr2], foram os que apresentaram os melhores resultados em termos de estabilidade e reprodutibilidade de resposta, escolhendo-se o EPCM-[MnPyr2], para uso neste trabalho. O desempenho do eletrodo foi avaliado usando voltametria cíclica, cronoamperometria e análise em fluxo, com detecção amperométrica de peróxido de hidrogênio apresentando regiões lineares de 1,25-14,8; 0,5-41; 1,0-75 x 10-4 mol L-1 e limites de detecção de 11,2; 2,98; 5,40 x 10-5 mol L-1 respectivamente para cada técnica. Na determinação de peróxido de hidrogênio em amostra de alvejante comercial observou-se concordância nos resultados obtidos em voltametria cíclica e análise em fluxo, usando o eletrodo proposto em comparação com a permanganometria clássica, com 95 % de intervalo de confiança. Estes resultados foram obtidos após otimização de parâmetros como velocidade de varredura, pH, eletrólito suporte, entre outros. A oxidação ocorre por meio de um processo eletrocatalítico. O desempenho do pirrolidinoditiocarbamato de vanadila hidratado também foi avaliado como alternativa aos ditiocarbamatos anidros, na preparação de eletrodos modificados com esta classe de complexos, considerando que os complexos hidratados seriam mais fáceis de preparar. Entretanto uma baixa estabilidade e reprodutibilidade de resposta foi observada. O [MnPyr2] mostrou comportamento no qual ocorre oxidação, concordando com a proposta de Schrauzer para ligantes do tipo ímpar, apesar de que a oxidação só ocorreu na presença de oxidantes fortes, como o peróxido de hidrogênio. / Considering their low solubility in water, the dithiocarbamate complexes should produce electrodes without problems of modifier leaching. Such electrodes could be used as amperometric detectors in flow injection analysis and hydrodynamic methods. The complex should act as an electron transfer mediator between the analyte and the electrode surface, improving the response sensitivity of the sensor. Considering these statements carbon paste electrodes modified (EPCM) with anhydrous pyrrolidinedithiocarbamates of several metals were prepared and evaluated in relation to their possible application in voltammetric techniques. Best results regarding response stability and reproducibility were obtained with manganese(II), [MnPyr2] and cobalt(II), [CoPyr2] complexes. The first one was chosen to develop the present work. The electrode performance was evaluated in cyclic voltammetry, chrono amperometric and flow injection analysis with amperometric detection. Linear dynamic ranges of 1,25-14,8; 0,5-41; 1,0-75 x 10-4 mol L-1 and limits of detection of 11,2; 2,98; 5,40 x 10-5 mol L-1 were found respectively for each technique in the determination of hydrogen peroxyde. The methods were used for the determination of H2O2 in bleaching formulation and presented agreement with the classical titration with potassium permanganate within 95% confidence level. Such results have been obtained after optimization of experimental parameters such as scan rate, pH, supporting electrolyte, and others. The oxidation occurred by an electrocatalytic process. Finally the performance of a carbon paste electrode modified with a hydrated vanadyl pyrrolidinedithiocarbamate complex was evaluated as an alternative to the anhydrous complex in the preparation of the modified electrode, since the hydrated complexes are easier to prepare. However a low response stability and reproducibility have been observed. The [MnPyr2] presented an oxidation behavior in agreement with Schrauzer’s predictions, although the oxidation of the metal center occurred only in the presence of strong oxidative agents as the hydrogen peroxide.

[Typewritten] Includes bibliography.

The thesis titled “Novel Strategies for the Synthesis of Organo-Sulfur Compounds Under Metal-free Reaction conditions” is presented into three main sections. Section A– deals with the synthesis of thiourea and thioamide. Section B– describes the sulfenylation of electron-rich arenes, ketones and β- diketones Section C– deals with the sulfur/fluorine assisted deacylation of α-sulfenylated β- diketones. Section A: This section is divided in to two chapters, Chapter 1 and Chapter 2. Chapter 1 of this section describes the non-isothiocyanate route to obtain trisubstituted thioureas of arylamines by using in situ generated dithiocarbamates of secondary amines. Trisubstituted thioureas of aryl amines are important precursors for the synthesis of heterocyles like 2-aminobenzothiazoles derivatives,1 amidines,2 and guanidines.3 Therefore, this strategy provides an excellent opportunity to access thioureas containing primary aryl amines without employing isothiocyanates. From the current method, the broad substrate scope was achieved with excellent yield of the corresponding products. Further, under the optimized reaction conditions a variety of functional groups like ketones, carboxylic acids, amides and sulfonamides were found to be well tolerated. A few representative examples are shown in Scheme 1.4 (a) Jordan, A. D.; Luo, C.; and Reitz, A. B. J. Org. Chem. 2003, 68, 8693. (b) Joyce, L. L.; Batey, R. A. Org. Lett. 2009, 11, 2792 and references therein. (c) Jamir, L.; Khatun, N.; Patel, B. K. RSC Adv., 2011, 1, 447. 1 Biswas, K.; Greaney, M. F. Org. Lett. 2011, 13, 4946. 2 (a) Wilson, L. J.; Klopfenstein, S. R.; Li, M. Tetrahedron Lett. 1999, 40, 3999. (b) Schneider, S. E.; Bishop, P. A.; Salazar, M. A.; Bishop, O. A.; Anslyn, E. V. Tetrahedron 1998, 54, 15063. 3 Varun, B. V.; Prabhu, K. R. RSC Adv.2013, 3, 3079. Synopsis Chapter 2 describes the rapid, high yielding and easily isolable method for the synthesis of thioamide by nucleophilic addition of electron-rich arenes to isothiocyanates. Thioamides are essential structural motifs which are found in a variety of biologically active molecules.5 They are also crucial building blocks for synthesizing sulfur conntaining heterocycles.6 The current method employs triflic acid (TfOH) to activate the nitrogen of isothiocyanate, where as, in the earlier methods AlCl3 was used.7 Also, the reaction was found to be highly regioselective and the broad substrate scope of the reaction was demonstrated (Scheme 2).85 (a) Cremlyn, R. J. An Introduction to Organosulfur Chemistry,John Wiley and Sons, Chichester, 1996. (b) Gottesman, M. M.; Fojo, T.; Bates, S. E. Nat. Rev. Cancer 2002, 2, 48; (c) Angehrn, P.; Goetschi, E.; Gmuender, H.; Hebeisen, P.; Hennig, M.; Kuhn, B.; Luebbers, T.; Reindl, P.; Ricklin, F.; Schmitt-Hoffmann, A. J. Med. Chem.2011, 54, 2207 6 (a)Shibuya, I.; Honda, K.; Gama, Y.; Shimizu, M. Heterocycles 2000, 53, 929. (b) Takido, T.; Itabashi, K.; Synthesis 1985, 430. (c) Shibuya, I.; Gama, Y.; Shimizu, M. Heterocycles 2001, 55, 381. (d) Wang, H.; Wang, L.; Shang, J.; Li, X.; Wang, H.; Gui, J.; Lei, A. Chem. Commun., 2012, 48, 76. (e) Alla, S. K.; Sadhu, P.; Punniyamurthy, T. J. Org. Chem., 2014, 79, 7502. (f) Chaudhari, P. S.; Pathare, S. P.; Akamanchi, K. G. J. Org. Chem., 2012, 77, 3716. (g) Mendoza-Espinosa, D.; Ung, G.; Donnadieu, B.; Bertrand, G. Chem. Commun.,2011, 47, 10614. (h) Potts, K. T.; Houghton, E.; Singh, U. P. J. Org. Chem., 1974, 39, 3627. 7 a) Jagodzinski, T.; Jagodzinska, E.; Jabłonski, Z. Tetrahedron 1986, (b) Jagodzinski, T. Synthesis 1988, 717. 8 Varun, B. V.; Sood, A.; Prabhu, K. R. RSC Adv.2014, 4, 60798. Scheme 2: Synthesis of thioamide Section B This section is divided in to two chapters, Chapter 1 and Chapter 2. Chapter 1 of this section describes a facile transition metal-free oxidative CDC (Cross Dehydrogenative Coupling) reaction leading to a regioselective thiolation of electron-rich arenes and hetero-arenes. This strategy provides a rare opportunity of using thione in a CDC reaction to form C–S bonds to obtain arylthiobenzoxazoles, hetero-arylthiobenzoxazoles and arylthiobenzthiazoles, which are pharmaceutically valuable compounds.9 This highly regioselective CDC reaction is unique as it requires the reversing the reactivity of sulfur to form the C–S bonds. Despite the propensity of thiols to undergo oxidation, this method provides an elegant and new avenue for synthesizing thioethers of benzazoles (Scheme 3).10 a) Greco, M. N.; Hageman, W. E.; Powell, E. T.; Tighe, J. J.; Persico, F. J. J. Med. Chem. 1992, 35, 3180. b) Zhang, J.-T.; Qi, J.; Feng, H.; Dong, Z. WO2010048603, 2010. c) Greco, M. N.; Hageman, W. E.; Powell, E. T.; Tighe, J. J.; Persico, F. J. J. Med. Chem. 1992, 35, 3180. d) Barchuk, W. T.; Dunford, P. J.; Edwards, J. P.; Fourie, A. M.; Karlsson, L.; Quan, J. M. US 2008194630. e) Koci, J.; Klimesova, V.; Waisser, K.; Kaustova, J.; Dahse, H.-M.; Moellmann, U.;Bioorg. Med. Chem. Lett. 2002, 12, 3275. 10 Varun, B. V.; Prabhu, K. R. J. Org. Chem.2014, 79, 9655. xii Synopsis Scheme 3: C-H-Functionalization of electron-rich arenes Chapter 2 is discussed in two parts, Part A and Part B. Part A: deals with the C–H functionalization of β-diketones via CDC reactions. A variety β-diketones were sulfenylated at α-position with a variety of benzazole-2-thione derivatives. Sulfenylation of β-diketones is challenging as β-diketones undergo deacylation after sulfenylation in the reaction medium.11 The highlight of this work is that the resultant products do not undergo deacylation. Under the optimal reaction conditions a variety of functional group like ketones, acids and esters were well tolerated. Also, the resultant sulfenylated β-diketones were further manipulated to α,α-disubstituted β-diketones and pyrazoles (Scheme 4).12 11 (a) Ogura, K.; Sanada, K.; Takahashi, K.; Iida, H. Tetrahedron Lett.1982, 23, 4035. (b) Zou, L.-H.; Priebbenow, D. L.; Wang, L.; Mottweiler, J.; Bolm, C. Adv. Synth. & Catal. 2013, 355, 2558. 12 Varun, B. V.; Gadde, K.; Prabhu, K. R. Org. Lett. 2015, 17, 2944. Scheme 4: C-H Functionalization of β-diketones via CDC reaction Chapter 2, Part B: deals with the C–H functionalization of ketones via CDC, which is the continuation of the above discussed work (Chapter 2, Part B). The products obtained from this method can be further modified and can be used for the synthesis of α,β-unsaturated carbonyl compounds under Trost or Julia olefination reaction conditions.13 A variety of actophenone derivatives, propiophenone derivatives and simple alkyl ketones were sulfenylated at the α-position with various benzazole-2-thiones (Scheme 5).14 Scheme 5: C-H Functionalization of ketones via CDC reaction (a) Trost, B. M.; Salzmann, T. N.; Hiroi, K. J. Am. Chem. Soc. 1975, 98, 4887. (b) Baudin, J. B.; Hareau, G.; Julia, S. A. Tetrahedron Lett. 1991, 32, 1175. (c) Blakemore, P. R.; Cole, W. J.; Kocienski, P. J.; Morley, A. Synlett 1998, 26. 14 Manuscript under preparation. Section C This section describes the ‘sulfur/fluorine assisted deacylation of β-diketones.’ Achieving a controlled mono fluorination at α- position of a ketone group is a difficult task. Therefore, an alternate approach is to have a sulfide group at α-position to a ketone (electron withdrawing moiety) and thereby providing additional stability to the generated reactive intermediate at α-position. Till date, this transformation has been achieved only by electrochemical methods.15 In continuation of our earlier work of α-sulfenyl β-diketones for exploring the synthetic utility of α-sulfenyl β-diketones (like benzylation and allylation), we performed the fluorination reaction. In this reaction, the fluorinated product (a diketone) underwent a de-acylation process to furnish the corresponding α-fluorinated ketone and we further optimized the reaction conditions and explored the substrate scope for this reaction. Under the optimized reaction conditions a variety of fluorinated products were isolated in excellent yield (Scheme 6) Scheme 6: Sulfur/Fluorine assisted deacylation of β-diketones 15Fuchigami, T.; Shimojo, M.; Konno, A.; Nakagawa, K. J. Org. Chem. 1990, 55, 6074 16 Manuscript under preparation.

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-09-20T14:54:53Z No. of bitstreams: 1 Teseseg.pdf: 4091406 bytes, checksum: 5c096537a6afa0dc26ceb33ccc3387b7 (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-09-20T15:53:19Z (GMT) No. of bitstreams: 1 Teseseg.pdf: 4091406 bytes, checksum: 5c096537a6afa0dc26ceb33ccc3387b7 (MD5) / Made available in DSpace on 2016-09-20T15:53:19Z (GMT). No. of bitstreams: 1 Teseseg.pdf: 4091406 bytes, checksum: 5c096537a6afa0dc26ceb33ccc3387b7 (MD5) / CNPQ / Os ditiocarbamatos (carboditioatos) têm sido muito utilizados em operações de pré-concentração de traços de metais por extração (líquido-líquido ou em fase sólida) e co-precipitação. No presente trabalho, apresentam-se os resultados encontrados com a co-precipitação de cobre, níquel, cobalto, chumbo e cádmio empregando piperazina-bis-ditiocarbamato, dietilditiocarbamato e N, N’dibenziletileno bisditiocarbamato sob a forma de compostos do zinco(II). Os reagentes foram preparados a partir da reação entre uma solução da amina correspondente, dissolvida em etanol, alcalinizada com NaOH e resfriada a 10OC com o dissulfeto de carbono (CS2). O precipitado que se forma é separado por filtração e pode ser usado como solução aquosa 1% (m/v) e pode ser conservado por mais de 15 dias. O zinco (II) reage com os ditiocarbamatos de sódio correspondentes e precipita, arrastando os demais metais. O procedimento pode ser executado com soluções com valores de pH entre 6,0 e 9,5 e não é afetado pela ordem de adição dos reagentes. O tempo de centrifugação para deposição da fase precipitada é de 15-30 minutos com uma rotação de 1000-2000 rpm. A co-precipitação simultânea de Cd, Co, Cu, Ni e Pb em níveis de 0,2 g/mL em alíquotas de 50,0 mL de água é possível empregando esta metodologia. As metodologias desenvolvidas foram aplicadas a amostras de água do mar e soluções salinas sintéticas (NaSO4, KCl, NaCl, Na2CO3). Os resultados mostram recuperações superiores a 90% para os metais, exceto para cobalto que tem recuperação superior a 90% apenas quando é empregada a ZnPDC como reagente em soluções salinas 1% (m/v). O método apresentou boa reprodutibilidade e tempo de análise de aproximadamente 4 horas. A metodologia com ZnPDC foi mais precisa para Co e Cu do que as outras metodologias. Sendo o ZnDDC o menos preciso para estes dois metais. Foram realizados experimentos com suporte sólido (naftaleno impregnado com ZnDDC) para a extração de Cd, Co, Cu, Ni e Pb. / The dithiocarbamates (carbodithioates) have been used in operations of pre-concentration of lines of metals by extraction (liquid-liquid or in solid phase) and co-precipitation. In the present work we presented results found for copper co-precipitation, nickel, cobalt, lead and cadmium using the zinc(II) compounds of piperazine-bis-dithiocarbamate, diethildithiocarbamate and N, N' dibenzylethylene bisdithiocarbamate. The reagents were prepared starting from the reaction among a solution of the corresponding amine dissolved in ethanol, alcalized with NaOH and caught a cold to 10O C, with the dissulfide of carbon (CS2). The precipitate that it forms was separated by filtration. The reagent is used as aqueous solution 1% (m/v) and it is stable by 15 days. The zinc (II) reacts with the sodium dithiocarbamates corresponding and co-precipitating with the other metals. The procedure can be executed with solutions with pH values between 4.0 and 10.0, and it is not affected by the order of addition of the reagents. The time of centrifugation is of 15-30 minutes with a rotation of 1000-2000 rpm. A simultaneous co-precipitation of Cd, Co, Cu, Ni and Pb in levels of 0.2 µg/mL in aliquots of 50.0 mL of water are possible using this methodology. The developed methodologies were applied the samples of water of the sea and synthetically saline solution s (NaSO4, KCl, NaCl, Na2CO3). The results show recoveries up to 90%, except for cobalt that has recovery around 90% only when the ZnPDC was used as reagent in saline solutions 1%. The method showed god reproducibility and the time’s analysis during around four hours. The methodology using ZnPDC was more precise to Co and Cu than the others methodologies. The ZnDDC was the less precise for these two metals. We also used a solid support (naphtalene impregnated with ZnDDC) for the extraction of Cd, Co, Cu, Ni and Pb.

Made available in DSpace on 2014-07-29T15:22:58Z (GMT). No. of bitstreams: 1 marcia regina ribeiro alves.pdf: 452897 bytes, checksum: 176d4d065ab6a2068b7a4fde3b142306 (MD5) Previous issue date: 2008-05-08 / Fungicides are the pesticides mostly used the tomato crop. Among the fungicides the dithiocarbamates are the mostly used. The objective of this work was to study the efficiency of the dithiocarbamate mancozeb removal from tomatoes through processes of washes. We performed analyses of acidity, brix, the activity of water (aw), pH and content of manganese for tomatoes. After completing the procedures of the fruit flush with tap water, vinegar, alcohol, and sodium bicarbonate solution of sodium dichloroisocyanurate dihydrate the level of the fungicide mancozeb was assessed in skin and whole fruit. It was observed that the process of the fruit flush significantly reduces the amount of residues in tomatoes. The reduction of mancozeb was higher in the skin, which are present in highest concentration. The treatments using tap water and sodium bicarbonate removed over 61% of the residue present in the skin of tomatoes / Dentre os agrotóxicos mais utilizados na cultura do tomate estão os fungicidas e, dentre estes, os mais aplicados na cultura são os ditiocarbamatos. O objetivo deste trabalho foi estudar a eficiência da remoção do ditiocarbamato mancozeb em tomates através de processos de enxágüe. Foram realizadas análises de acidez, brix, da atividade de água (aw), pH e teor do manganês para os tomates. Após realização do processos de enxágüe do fruto com água de torneira, vinagre de álcool, bicarbonato de sódio e solução de dicloroisocianurato de sódio dihidratado foi avaliado o teor do fungicida mancozeb na película e fruto inteiro. Observou-se que o processo de enxágüe do fruto reduz significativamente a quantidade resíduos nos tomates. A redução de mancozeb foi maior na película, onde estão presentes em maior concentração. Os tratamentos usando água de torneira e bicarbonato de sódio removeram acima de 61% dos resíduos presentes na película dos tomates

Devido à sua baixa solubilidade em água, os pirrolidinoditiocarbamatos poderiam produzir eletrodos livres do problema de lixiviação do modificador, os quais poderiam ser usados como detectores amperométricos, em análises em fluxo e outros procedimentos hidrodinâmicos. O complexo poderia agir como um intermediário de transferência de elétrons entre o analito e a superfície eletródica, aumentando a sensibilidade da resposta analítica do sensor. Desta forma, eletrodos de pasta de carbono modificados (EPCM) com complexos de pirrolidinoditiocarbamatos anidros de diversos metais foram preparados e testados quanto à sua aplicação em técnicas voltamétricas. Os complexos de manganês(II), [MnPyr2] e cobalto(II), [CoPyr2], foram os que apresentaram os melhores resultados em termos de estabilidade e reprodutibilidade de resposta, escolhendo-se o EPCM-[MnPyr2], para uso neste trabalho. O desempenho do eletrodo foi avaliado usando voltametria cíclica, cronoamperometria e análise em fluxo, com detecção amperométrica de peróxido de hidrogênio apresentando regiões lineares de 1,25-14,8; 0,5-41; 1,0-75 x 10-4 mol L-1 e limites de detecção de 11,2; 2,98; 5,40 x 10-5 mol L-1 respectivamente para cada técnica. Na determinação de peróxido de hidrogênio em amostra de alvejante comercial observou-se concordância nos resultados obtidos em voltametria cíclica e análise em fluxo, usando o eletrodo proposto em comparação com a permanganometria clássica, com 95 % de intervalo de confiança. Estes resultados foram obtidos após otimização de parâmetros como velocidade de varredura, pH, eletrólito suporte, entre outros. A oxidação ocorre por meio de um processo eletrocatalítico. O desempenho do pirrolidinoditiocarbamato de vanadila hidratado também foi avaliado como alternativa aos ditiocarbamatos anidros, na preparação de eletrodos modificados com esta classe de complexos, considerando que os complexos hidratados seriam mais fáceis de preparar. Entretanto uma baixa estabilidade e reprodutibilidade de resposta foi observada. O [MnPyr2] mostrou comportamento no qual ocorre oxidação, concordando com a proposta de Schrauzer para ligantes do tipo ímpar, apesar de que a oxidação só ocorreu na presença de oxidantes fortes, como o peróxido de hidrogênio. / Considering their low solubility in water, the dithiocarbamate complexes should produce electrodes without problems of modifier leaching. Such electrodes could be used as amperometric detectors in flow injection analysis and hydrodynamic methods. The complex should act as an electron transfer mediator between the analyte and the electrode surface, improving the response sensitivity of the sensor. Considering these statements carbon paste electrodes modified (EPCM) with anhydrous pyrrolidinedithiocarbamates of several metals were prepared and evaluated in relation to their possible application in voltammetric techniques. Best results regarding response stability and reproducibility were obtained with manganese(II), [MnPyr2] and cobalt(II), [CoPyr2] complexes. The first one was chosen to develop the present work. The electrode performance was evaluated in cyclic voltammetry, chrono amperometric and flow injection analysis with amperometric detection. Linear dynamic ranges of 1,25-14,8; 0,5-41; 1,0-75 x 10-4 mol L-1 and limits of detection of 11,2; 2,98; 5,40 x 10-5 mol L-1 were found respectively for each technique in the determination of hydrogen peroxyde. The methods were used for the determination of H2O2 in bleaching formulation and presented agreement with the classical titration with potassium permanganate within 95% confidence level. Such results have been obtained after optimization of experimental parameters such as scan rate, pH, supporting electrolyte, and others. The oxidation occurred by an electrocatalytic process. Finally the performance of a carbon paste electrode modified with a hydrated vanadyl pyrrolidinedithiocarbamate complex was evaluated as an alternative to the anhydrous complex in the preparation of the modified electrode, since the hydrated complexes are easier to prepare. However a low response stability and reproducibility have been observed. The [MnPyr2] presented an oxidation behavior in agreement with Schrauzer’s predictions, although the oxidation of the metal center occurred only in the presence of strong oxidative agents as the hydrogen peroxide.

In order to supply the world-wilde demand for food, it is essential to use the pesticides to protect the crops against pests and diseases. But the indiscriminate and injudicious use of these compounds have resulted in widespread contamination in food commodities and environment in all fields, increasing, this way, the preoccupation with chemical products use. Ethylene-bis-dithiocarbamate pesticides, from dithiocarbamate class, are among the most widely used fungicide to control pest. Beside their low toxicity, one of they degradation products, ethylenethiourea, is a toxic metabolite, which have teratogenic, carcinogenic, immunotoxic and mutagenic effects. In the present work, it was developed and validated a chromatographic method for the determination of ethylenethiourea (ETU) residues in urine, using liquid-liquid extraction and HPLC quantification. The developed procedure consist of the interested compound extraction from urine, with 6.0 mL of dichloromethane, aditioning MgSO4 to help in the partitioning process, that is, distribution os compound between organic and aqueous phase. After sample centrifugation, a supernatant aliquot was taken and evaporated, in water bath at 44 ºC, and the final extract was redissolved in purified water and analyzed by HPLC-UV, injecting 50 μL in C18 column with mobile phase MeOH:H2O (10:90; v/v) and detection by UV light absorption at 233 nm. To the validation study of the method, the following parameters were evaluated: detection limit (LOD), quantification limit (LOQ), precision (under repeatability and reproducibility conditions) and accuracy as recovery. The method LOD was 0.05 mg ETU L-1 and LOQ was 0.2 mg ETU L-1. The analytical curve was linear between 0.05 to 1.0 mg ETU L-1 with determination coefficient r2 > 0.998. Very good precision with RSD between 1.7 and 2.7% was obtained and the recoveries ranged from 85.6 to 95.4% for 3 different spike level: 0,05, 0,1 and 0,5 mg ETU L-1 . The results obtained in the validation step allow us to conclude that the method are quite appropriate to determine residue of ethylenethiourea in urine. The developed method has shown advantages, such as simplicity, quickness and that it could be applied in any laboratory. However, there are some points such as no ETU confirmation nether purity analysis of the chromatographic picks besides the low sensitivity and selectivity of the UV detection that would be much improved using a LC-MS/MS. / Para atender a demanda mundial por alimentos, é essencial o emprego de pesticidas para proteger as culturas contra doenças e pragas, mas o uso imprudente e indiscriminado destes compostos pode resultar em contaminação dos alimentos e seus derivados, bem como no ambiente como um todo, aumentando, dessa forma, a preocupação em relação ao emprego dos pesticidas. Os pesticidas etileno-bisditiocarbamatos, da classe dos ditiocarbamatos, estão entre os fungicidas mais empregados em todo o mundo para o controle de pragas. Apesar de possuírem baixa toxicidade, um de seus produtos de degradação, a etilenotiouréia (ETU), é um metabólito tóxico, a qual possui efeitos teratogênicos, carcinogênicos, imunotóxicos e mutagênicos. Neste trabalho, desenvolveu-se e validou-se um método cromatográfico para a determinação dos resíduos de ETU em urina, empregando-se extração líquidolíquido e quantificação por HPLC-UV. O procedimento desenvolvido consiste na extração do analito de interesse, com 6 mL de diclorometano, adicionando-se MgSO4 para auxiliar no processo de partição, ou seja, distribuição do composto entre as fases orgânica e aquosa. Posteriormente, centrifugou-se e evaporou-se uma alíquota do sobrenadante em banho de água à 44 ºC, redissolvendo-se em água purificada e analisa-se em sistema HPLC, injetando-se 50 μL em coluna C18 com fase móvel MeOH:H2O (10:90; v/v) e detecção por absorção de luz em 233 nm. Para a validação do método avaliaram-se os seguintes parâmetros: limite de detecção (LOD), limite de quantificação (LOQ), linearidade, precisão (repetitividade e precisão intermediária) e exatidão (recuperação). O LOD do método foi de 0,05 mg ETU L-1 e o LOQ 0,2 mg ETU L-1. As curvas analíticas apresentaram r2 > 0,998 com linearidade entre 0,05 e 1,0 mg ETU L-1. Os resultados de precisão foram excelentes, com valores de desvio padrão relativo entre 1,7 e 2,7%, e as recuperações foram de 85,6 a 95,4% para 3 níveis de fortificação: 0,05, 0,1 e 0,5 mg ETU L-1. Através dos resultados obtidos na validação, pode-se concluir que o método é apropriado para determinar resíduos de etilenotiouréia em urina. O método tem várias vantagens como: simplicidade, rapidez, e poder ser executado com equipamentos geralmente disponíveis nos laboratórios. Entretanto, poderia apresentar resultados ainda melhores em termos de sensibilidade, seletividade e confirmação da identidade da ETU, se fosse possível, por exemplo, a utilização de cromatógrafo à líquido acoplado à espectrômetro de massas, onde a pureza dos picos cromatográficos poderia ser avaliada e a detectabilidade poderia ser 3 ordens de magnitude menor (1000 vezes).

Abstract The rare-earth elements (REEs) and bismuth, being classified as the ‘most critical raw materials’ (European Raw Materials Initiatives, 2017), have a high economic importance to the EU combined with a high relative supply risk. REEs are highly important for the evolving technologies such as clean-energy applications, high-technology components, rechargeable batteries, permanent magnets, electric and hybrid vehicles, and phosphors monitors. This scientific research work aims at building a fundamental knowledge base concerning the electronic/molecular structure and properties of rare-earth element (REE) and bismuth complexes with dithiocarbamate (DTC) and 1,10-phenanthroline (PHEN) by employing state-of-the-art experimental techniques such as nuclear magnetic resonance (NMR) spectroscopy and X-ray diffraction (XRD) techniques together with ab initio quantum mechanical computational methods. This combination of methods has played a vital role in analysing the direct and significant effect of the heavy metal ions on the structural and magnetic resonance properties of the complexes, thereby, providing a framework of structure elucidation. This is of special importance for REEs, which are known to exhibit similar chemical and physical properties. The objectives of the work involve i) a systematic investigation of series of REE(III) as well as bismuth(III) complexes to get a profound understanding of the structure-properties relationship and ii) to find an appropriate theoretical modelling and NMR calculation methods, especially, for heavy metal systems in molecular and/or solid-state. This information can later be used in surface interaction studies of REE/bismuth minerals with DTC as well as in design and development of novel ligands for extraction/separation of metal ions. The REE(III) and bismuth(III) complexes with DTC and PHEN ligands have all provided a unique NMR fingerprint of the metal centre both in liquid and solid phase. The solid-state ¹³C and ¹⁵N NMR spectra of the diamagnetic REE(III) and bismuth(III) complexes were in accord with their structural data obtained by single crystal XRD. The density functional theory (DFT) methods were used to get complementary and refined structural and NMR parameters information for all diamagnetic complexes in the solid-state. The relativistic contributions due to scalar and spin-orbit correlations for the calculated ¹H/¹³C/¹⁵N chemical shifts of REE complexes were analysed using two-component zeroth-order regular approximation (ZORA)/DFT while the ‘crystal-lattice’ effects on the NMR parameters were calculated by combining DFT calculations on molecular and periodic solid-state models. The paramagnetic REE complexes display huge differences in their ¹H and ¹³C NMR spectral patterns. The experimental paramagnetic NMR (pNMR) chemical shifts, as well as the sizable difference of the ¹H and ¹³C NMR shifts for these isoelectronic complexes, are well reproduced by the advanced calculations using ab initio/DFT approach. The accuracy of this approach is very promising for further applications to demanding pNMR problems involving paramagnetic f-block elements. The results presented in this thesis demonstrate that a multidisciplinary approach of combined experimental NMR and XRD techniques along with computational modelling and property calculations is highly efficient in studying molecular complexes and solids containing heavy metal systems, such as rare-earths and bismuth.

Etilenotiouréia (ETU) é uma substância tóxica, formada pela degradação e/ou biotransformação dos fungicidas etilenobisditiocarbamatos (EBDC). Seus resíduos podem ser encontrados em plantas e no ambiente, após o uso de EBDC na agricultura, ou em animais e no ser humano, quando expostos a esses produtos. Comprovadamente, a ETU tem a capacidade de induzir tumor na tireóide de roedores e no fígado de camundongo, apresentando evidência suficiente para carcinogenicidade em animais e evidência inadequada para carcinogenicidade em seres humanos. Os objetivos deste estudo foram: validar método analítico para determinação de resíduos de ETU nas matrizes estudadas; verificar a presença de resíduos de ETU em amostras de frutas (mamão, maçã e morango), coletadas em diferentes pontos de comercialização da cidade de São Paulo; avaliar os resultados e a contribuição de risco à saúde da população consumidora. Foram analisadas 90 amostras, sendo 30 de cada fruta (maçã, mamão e morango), adquiridas em diferentes pontos de comercialização da cidade São Paulo, no período de dezembro de 2005 a dezembro de 2006, distribuídas nas diferentes regiões do referido município e durante as estações do ano. Os parâmetros de validação avaliados foram: seletividade, linearidade, limite de quantificação, limite de detecção, exatidão e precisão. Os estudos de recuperação foram realizados com fortificações em três níveis (1, 2 e 10 LQ) em amostras controle. A determinação de resíduos de ETU foi feita por cromatografia a líquido de alto desempenho, com detector de absorção no ultravioleta (HPLC-UV) e cromatografia a líquido acoplada à espectrometria de massas em tandem (LC/MS/MS). Como todos os resultados obtidos por HPLC-UV apresentaram níveis de ETU abaixo do LQ limite de quantificação (10,0?g/kg), as quantificações foram realizadas no LC/MS/MS, com limite de quantificação e de detecção respectivamente de 1,0?g/kg e 0,5?g/kg. O método por LC/MS/MS mostrouse adequado para análise de ETU nos níveis de até 2,0?g/kg para maçã e morango e de até 10,0 ?g/kg para mamão, com recuperações médias de 75 a 110% e coeficientes de variação de 6 a 17%. Foram encontrados resíduos de ETU em 10 (33%) das amostras de maçã, em níveis que variaram de 1,0 a 3,7 ?g/kg (ppb); em 20 (67%) das amostras de mamão, de 1,0 a 5, 3?g/kg; em 2 (7%) das amostras de morango, de 1,0 a 1,4 ?g/kg. Estes valores estão abaixo do limite de 50?g/kg, estabelecido na União Européia. A estimativa da ingestão de resíduos de ETU pelo consumo das frutas estudadas, considerando o maior nível encontrado nesta pesquisa e dados fornecidos pelo IBGE, representam respectivamente 0,05 e 0,20 % da IDA (Ingestão Diária Aceitável, estabelecida pelo Codex Alimentarius), para a população em geral e crianças. A estimativa da ingestão de resíduos de EBDC pelo consumo dos alimentos (maçã, tomate, mamão, alface, morango, banana, laranja, cenoura), monitorados pelo PARA no período de 2001 a 2004, considerando os maiores níveis encontrados e 100% dos resíduos de ditiocarbamatos (CS2) como sendo originários do uso de EBDC, foi de 7,2% para a população em geral e de 28,9 % para crianças. Dados de ETU e EBDC em outros alimentos, incluindo os industrializados, em água de consumo e em amostras ambientais, além de dados mais refinados de consumo alimentar para subgrupos mais sensíveis (como crianças e mulheres grávidas), são necessários para se avaliar o risco de maneira mais global e condizente com a realidade, em prol da Saúde Pública. / Ethylene thiourea (ETU) is a toxic substance generated by the degradation and/or biotransformation of ethylenebisdithiocarbamates (EBDC) fungicides. Their residues may be found in plants and in the environment after EBDC's use in agriculture or in animals and humans when exposed to such products. ETU is confirmedly able to induce tumors in rodents' thyroids and in mouse's liver, showing enough evidence of carcinogenicity in animals and inadequate evidence of carcinogenicity in humans. The aims of this study were validating an analytical method for determining ETU residues in the studied sources, verifying the presence of ETU residues in fruit samples (papaya, apple and strawberry) collected from different commercial centers in the city of São Paulo; evaluating the results and their contribution as a risk to the consumers' health. Ninety fruit samples (30 samples of each fruit - papaya, apple and strawberry) were analyzed. The samples were purchased at different commercial centers in different regions of the city of São Paulo and over all seasons during December 2005 through December 2006. The validation parameters used were selectivity, linearity, accuracy and precision. Recovery studies were carried out with fortifications in 3 levels (1, 2 and 10 times the Limit of Quantification, LQ) in control samples. The determination of ETU residues was carried out by high performance liquid chromatography, ultra-violet absorption detector (HPLC/UV) and liquid chromatography coupled on tandem mass spectrophotometry (LC/MS/MS). Since all results obtained through HPLC/UV showed levels of ETU below the LQ (10.0 ?g/kg), quantification were carried out through LC/MS/MS with quantification and detection limits of 1.0?g/kg and 0.5 ?g/kg, respectively. The LC/MS/MS method proved adequate for analyzing quantities of ETU as low as 2.0 ?g/kg in apple and strawberry and 10.0 ?g/kg in papaya, with average recovery of 75 to 110 % and variation coefficients of 6 to 17 %. ETU residues were found in 10 (33%) apple samples with levels ranging from 1.0 to 3.7 ?g/kg (ppb); in 20 (67%) of papaya samples with levels ranging from 1.0 to 5.3 ?g/kg (ppb); and in 2 (7%) strawberry samples with levels ranging from 1.0 to 1.4 ?g/kg (ppb). These values are below the limit established in European Community (50 ?g/kg). The assessment of ETU intake, considering the consumption informed by IBGE (Instituto Brasileiro de Geografia e Estatística, the Brazilian Institute for Geography and Statistics) and the highest level observed in total fruit samples in this research, represent 0.05 % and 0.20 % ADI (Acceptable Daily Intake, established by the Codex Alimentarius) for geral population and children, respectively. The assessment of EBDC intake, considering the consumption informed by IBGE (Instituto Brasileiro de Geografia e Estatística, the Brazilian Institute for Geography and Statistics) and the highest level observed in food samples (apple, tomato, papaya, lettuce, strawberry, banana, orange, carrot), monitoring from 2001 through 2004 year in the PARA (Programa de Análise de Resíduos de Agrotóxicos em Alimentos, Program Monitoring of Pesticide Residues in Food, Brazil), and that 100% of dithiocarbamate (CS2) residues from EBDC's use, represent 7.2% and 28.9% ADI for geral population and children, respectively. ETU and EBDC data in other foods (including industrialized foods), water and environment samples, together with more refined food consumption data considering more sensitive population subgroups (as children and pregnants) are necessary to evaluate the risk in a more global and realistic way in favor of Public Health.