Improved procedures for the glycosylation of serine and threonine utilizing Schiff base activation are reported. The procedures are less expensive and more efficient alternatives to previously published methods. The Schiff bases exhibited ring-chain tautomerism in CDCl₃ as shown by ¹H NMR. Acting as glycosyl acceptors, the Schiff bases reacted at RT with simple sugar peracetate donors with BF₃•OEt₂ promotion to provide the corresponding protected amino acid glycosides in good yields. With microwave irradiation, the reactions were complete in 2-5 minutes. Glycosylation with the dipeptide Schiff base shows the potential of this method in the preparation of peptide building blocks. To investigate this reaction further, direct glycosylation of sugar acetates with FMOC-Ser-OH/OBZl under BF₃•OEt₂ promotion in a microwave provided glycosides in high yield. In addition to the expected glycoside products acetylated side products resulting from acetate migration were isolated, suggesting that activation of the anomeric sugar acetates with a Lewis acid such BF₃•OEt₂ led to an oxocarbenium ion, which rearranged to a 1,2-dioxocarbenium ion because of the acetate participating group at C-2. Solvent participation was also illustrated with acetate migration being more pronounced when CH₃CN was used as a solvent and resulted in less product yield and higher amounts of the acetylated product. The acyl transfer products in these reactions where sugar acetates serve as glycosyl donors is reported for the first time, which also implies that ortho-ester like intermediates are important in the reaction mechanism. Keeping the message segment constant in the sequence H-Tyr-DThr-Gly-Phe-Leu- Ser-CO-NH₂ and modification of the address segment with different carbohydrate moieties had little effect on selectivity for binding at the μ, δ, or κ-opiod receptors. However, substitution of D-threonine with D-serine or the less polar D-alanine in the message segment resulted in a loss of κ-receptor affinity. Further replacement of D-threonine with the more hydrophobic D-valine resulted in complete loss of κ-binding affinity generating pure μ-δ agonists. These data suggests that changes in the message segment of the pharmacophore results in the glycopeptide adopting a conformation that is less favorable for 􀀁-binding receptor activity. Finally, the peripheral administration and i.c.v. tests of the drugs suggest that modifications in the message segment of the pharmacophore influences the potency of these compounds.

Single-Molecule Magnets (SMMs) are discrete molecules that exhibit slow relaxation of magnetization. Unlike conventional magnets that rely on the long range magnetic ordering in the form of domains, these molecules act as magnets independently, that is without the influence of neighbouring molecules. SMMs have intrigued physicists and chemists alike for over twenty years with their potential future applications in data storage quantum computing, and with this communal interest there has been significant collaboration between the two fields of research. SMMs have brought forth an opportunity for coordination chemists to muster their creativity and synthetic expertise in the rational design and development of these magnetic materials. From these new and fascinating compounds, both experimental and theoretical physicists have sought to develop and refine our understanding of the aspects of these molecular magnets in order to improve their performance at higher temperatures. In this work, new topologies for lanthanide complexes are explored using a novel Schiff base ligand. The magnetic properties of dinuclear, tetranuclear and octanuclear lanthanide complexes are discussed and correlated to their structural properties. The rational design of tetrazine-based Schiff base ligands for magnetic studies is also discussed in hopes of developing high performance SMMs.

This thesis describes the synthesis, characterization and magnetic investigation of homometallic lanthanide complexes based on two different o-vanillin-derived Schiff base ligands: H2ovph and H2ovgrd. The studies were performed using single crystal X-ray diffractometry, Powder XRD and SQUID magnetometry. Chapter 2 focuses on dinuclear systems 1-8 coordinated to the ligand H2ovph and presents their structural and magnetic properties, mainly with respect to their intramolecular interactions. Chapter 3 describes two hexanuclear systems, 9 (DyIII) and 10 (GdIII), with trigonal prism-assembled core structures. A structural comparison to other similar complexes in the literature is performed. A series of dinuclear complexes, 11-15, based on the ligand H2ovgrd are described in Chapter 4, focusing on the synthetic strategy, crystal structures and magnetism. The presence of the lanthanide contraction is evident in this system of complexes and is consistent with the intrinsic lanthanide contraction property.

The work presented in this Thesis describes the design, synthesis and reactivity of a symmetric and various asymmetric Schiff-base macrocycles that are capable of forming a wedge-shaped “Pacman” conformation upon metal binding. Chapter One introduces catalysts for small molecule transformation as well as transition metal complexes of pyrrole-containing macrocycles. Further to this, Pacman systems, including previous work from Love and co-workers, and complexes capable of secondary coordination-sphere control will be discussed. Chapter Two details the design and synthesis of two asymmetric macrocycles that both contain one neutral and one N₄-donor imine-pyrrole binding pocket, H₂LP and H₂LNMe. The synthesis and characterisation of the series of complexes [M(LP)] and [M(LNMe)] (M = Pd, K₂, Co, VCl, TiCl, Mg, Fe and Mn) and their characteristics highlighted, including the formation of a supramolecular cyclic hexamer. Chapter Three presents the modification of the above ligands at the meso-group, the N-substituent and the non-pyrrolic binding pocket to give H2LFP and H₂LFNMe, H₂LNMes and H₂L(NH)NMe respectively. Palladium and cobalt complexes of these macrocycles were prepared and characterised. Chapter Four describes the design and synthesis of the ligand H₄LEt as well as the synthesis and characterisation of tin-alkyl and mononuclear calcium complexes of LEt, as well as the heterobimetallic complexes [SnMe₂(M)(THF)(LEt)] (M = Zn or Fe). The homobimetallic complexes [M₂(LEt)] (M = Co, Mg and NbCl) are also presented along with a magnesium-cubane structure of LEt in which the cubane is encapsulated by two, bowl-shaped macrocycles. Chapter Five provides a summary of the work presented in this thesis. Chapter Six describes the full experimental details and analytical data for all compounds synthesised in this work.

Bases de Schiff biopoliméricas à base de quitosana foram preparadas a partir do salicilaldeído e de seus derivados substituídos na posição 5 do anel aromático do salicilaldeído (5-bromo, 5-cloro, 5-metil, 5-metóxi e 5-nitrosalicilaldeído), utilizando condições de síntese otimizadas para aumentar o grau de substituição (GS). Durante a caracterização das bases foram observados GS (%) = 78,7; 51,3; 43,7; 28,1; 22,1 e 17,5, respectivamente para os derivados 5-metóxi, salicilaldeído, 5-nitro, 5-cloro, 5-metil e 5-bromo, tendo sido as diferenças atribuídas ao caráter indutivo e de ressonância de cada um dos grupos substituintes. A partir desses ligantes foram sintetizados os complexos de cobre (II) e níquel (II) com quitosana e todas as bases de Schiff biopoliméricas. A quitosana, os ligantes e os complexos foram caracterizados por espectroscopia vibracional na região do infravermelho com transformada de Fourier (FTIR) e técnicas termoanalíticas (termogravimetria, TG; termogravimetria derivada, DTG e análise térmica diferencial, DTA). A quitosana utilizada apresentou grau de desacetilação, GD = 75,6%, determinado por 1H RMN, e apresentou as bandas características para estes biopolímeros nos espectros FTIR e decomposição térmica em dois eventos exotérmicos, após desidratação. As curvas TG/DTG-DTA das bases revelaram que estas são menos estáveis que a quitosana de partida e a estabilidade mostrou-se mais uma função da natureza do ligante do que do GS. A partir das curvas TG e dos valores de GS foi possível prever a composição das bases em concordância com os dados de análise elementar. Os complexos mostraram coordenação com os átomos de oxigênio do anel aromático dos aldeídos e do nitrogênio imínicos, com base nos espectros FTIR, sendo os complexos de cobre aparentemente mais fortes que os de níquel, se considerados os deslocamentos nas frequências de vibração das ligações C=N e C-Ofen. Os complexos de cobre (II) e níquel (II) também apresentaram decomposição em duas etapas, após desidratação, tendo sido a primeira etapa observada em temperaturas inferiores às das bases. Em alguns casos foi possível observar que os processos de decomposição se dividem, sugerindo decomposição diferenciada para regiões do biopolímero contendo o complexo e aquelas não modificadas, pois tal fenômeno ocorreu principalmente nos complexos derivados das bases com menor GS. Os resíduos de decomposição desses complexos foram CuO e NiO, de acordo com difratogramas de raios X, cujos teores permitiram calcular a quantidade de metal presente em cada complexo, e concluir que praticamente todos os sítios contendo as bases biopoliméricas foram complexadas em ambos os casos. / Biopolymeric Schiff bases were prepared from chitosan and salicylaldehyde and its 5-bromo, 5-chloro, 5-methyl, 5-methoxy and 5-nitro derivatives, under conditions optimized to improve the degree of substitution (DS). From 1H NMR data, DS (%) = 78.7, 51.3, 43.7, 28.1, 22.1 and 17.5, for 5-methoxy, salicylaldehyde, 5-nitro, 5-chloro, 5-methyl, and 5-bromo derivatives, respectively. The differences had been attributed to inductive and resonance effects of each substituent. From these ligands, copper (II) and nickel (II) complexes were synthesized with chitosan and all the biopolymeric Schiff bases. Chitosan, ligands and complexes were characterized by Fourier transform vibrational spectroscopy in the infrared region (FTIR) and thermal analytical techniques (thermogravimetry, TGA; derivative thermogravimetry, DTG and differential thermal analysis, DTA). Chitosan presented a deacetylation degree, DD = 75.6%, determined by 1H NMR, presenting the characteristic bands of this biopolymer in the FTIR spectra as well as decomposition in two exothermic steps after dehydration. TGA/DTG and DTA curves of the bases revealed that they are less stable than chitosan. This stability is closely related to the nature of substituent than the DS. From TGA curves and DS values it was possible to calculate the bases composition which agreed with elemental analysis data. Complexes presented coordination via oxygen atom of aldehydes aromatic rings and the iminic nitrogen, based on the FTIR results, being the copper (II) complexes apparently stronger the those from nickel (II), if one consider the displacements in the vibration frequencies of the C=N and C-Ophen bonds. The copper (II) and nickel (II) complexes also presented decomposition in two steps after dehydration, being the first step observed in lower temperatures when compared to those of the free bases. In some cases it was possible to observe that the decomposition steps in the DTG curves are split suggesting different decomposition for regions of the biopolymer in which the complexes is present and for the unmodified ones, once such phenomena occurred mainly in complexes derived from the bases with lower DS. The residues of decomposition for such complexes were CuO and NiO, according to X-ray diffractograms and their contents permitted to calculate the amount of each metal present in the complex leading to conclude that almost all the sites containing the Schiff bases on the biopolymeric matrix was complexed in both cases.

Bases de Schiff biopoliméricas à base de quitosana foram preparadas a partir do salicilaldeído e de seus derivados substituídos na posição 5 do anel aromático do salicilaldeído (5-bromo, 5-cloro, 5-metil, 5-metóxi e 5-nitrosalicilaldeído), utilizando condições de síntese otimizadas para aumentar o grau de substituição (GS). Durante a caracterização das bases foram observados GS (%) = 78,7; 51,3; 43,7; 28,1; 22,1 e 17,5, respectivamente para os derivados 5-metóxi, salicilaldeído, 5-nitro, 5-cloro, 5-metil e 5-bromo, tendo sido as diferenças atribuídas ao caráter indutivo e de ressonância de cada um dos grupos substituintes. A partir desses ligantes foram sintetizados os complexos de cobre (II) e níquel (II) com quitosana e todas as bases de Schiff biopoliméricas. A quitosana, os ligantes e os complexos foram caracterizados por espectroscopia vibracional na região do infravermelho com transformada de Fourier (FTIR) e técnicas termoanalíticas (termogravimetria, TG; termogravimetria derivada, DTG e análise térmica diferencial, DTA). A quitosana utilizada apresentou grau de desacetilação, GD = 75,6%, determinado por 1H RMN, e apresentou as bandas características para estes biopolímeros nos espectros FTIR e decomposição térmica em dois eventos exotérmicos, após desidratação. As curvas TG/DTG-DTA das bases revelaram que estas são menos estáveis que a quitosana de partida e a estabilidade mostrou-se mais uma função da natureza do ligante do que do GS. A partir das curvas TG e dos valores de GS foi possível prever a composição das bases em concordância com os dados de análise elementar. Os complexos mostraram coordenação com os átomos de oxigênio do anel aromático dos aldeídos e do nitrogênio imínicos, com base nos espectros FTIR, sendo os complexos de cobre aparentemente mais fortes que os de níquel, se considerados os deslocamentos nas frequências de vibração das ligações C=N e C-Ofen. Os complexos de cobre (II) e níquel (II) também apresentaram decomposição em duas etapas, após desidratação, tendo sido a primeira etapa observada em temperaturas inferiores às das bases. Em alguns casos foi possível observar que os processos de decomposição se dividem, sugerindo decomposição diferenciada para regiões do biopolímero contendo o complexo e aquelas não modificadas, pois tal fenômeno ocorreu principalmente nos complexos derivados das bases com menor GS. Os resíduos de decomposição desses complexos foram CuO e NiO, de acordo com difratogramas de raios X, cujos teores permitiram calcular a quantidade de metal presente em cada complexo, e concluir que praticamente todos os sítios contendo as bases biopoliméricas foram complexadas em ambos os casos. / Biopolymeric Schiff bases were prepared from chitosan and salicylaldehyde and its 5-bromo, 5-chloro, 5-methyl, 5-methoxy and 5-nitro derivatives, under conditions optimized to improve the degree of substitution (DS). From 1H NMR data, DS (%) = 78.7, 51.3, 43.7, 28.1, 22.1 and 17.5, for 5-methoxy, salicylaldehyde, 5-nitro, 5-chloro, 5-methyl, and 5-bromo derivatives, respectively. The differences had been attributed to inductive and resonance effects of each substituent. From these ligands, copper (II) and nickel (II) complexes were synthesized with chitosan and all the biopolymeric Schiff bases. Chitosan, ligands and complexes were characterized by Fourier transform vibrational spectroscopy in the infrared region (FTIR) and thermal analytical techniques (thermogravimetry, TGA; derivative thermogravimetry, DTG and differential thermal analysis, DTA). Chitosan presented a deacetylation degree, DD = 75.6%, determined by 1H NMR, presenting the characteristic bands of this biopolymer in the FTIR spectra as well as decomposition in two exothermic steps after dehydration. TGA/DTG and DTA curves of the bases revealed that they are less stable than chitosan. This stability is closely related to the nature of substituent than the DS. From TGA curves and DS values it was possible to calculate the bases composition which agreed with elemental analysis data. Complexes presented coordination via oxygen atom of aldehydes aromatic rings and the iminic nitrogen, based on the FTIR results, being the copper (II) complexes apparently stronger the those from nickel (II), if one consider the displacements in the vibration frequencies of the C=N and C-Ophen bonds. The copper (II) and nickel (II) complexes also presented decomposition in two steps after dehydration, being the first step observed in lower temperatures when compared to those of the free bases. In some cases it was possible to observe that the decomposition steps in the DTG curves are split suggesting different decomposition for regions of the biopolymer in which the complexes is present and for the unmodified ones, once such phenomena occurred mainly in complexes derived from the bases with lower DS. The residues of decomposition for such complexes were CuO and NiO, according to X-ray diffractograms and their contents permitted to calculate the amount of each metal present in the complex leading to conclude that almost all the sites containing the Schiff bases on the biopolymeric matrix was complexed in both cases.

Esta tese apresenta a obtenção de sílica xerogel a partir de carvão de cascas de arroz e a modificação da sua superfície com um ligante orgânico tipo base de Schiff. O objetivo da utilização deste resíduo agroindustrial é a obtenção de um adsorvente capaz de atuar no tratamento de águas contaminadas contendo íons cádmio II, em uma concepção de valorização de resíduos. A sílica contida na biomassa foi obtida na forma de silicato de sódio através de extração química com solução de hidróxido de sódio, seguida de hidrólise e condensação do monômero através do processo solgel. A modificação da superfície da sílica com o ligante salen foi realizada utilizando o 1,2-dicloroetano como espaçador bifuncional. A sílica xerogel modificada foi avaliada através de análises de isotermas de adsorção e dessorção de nitrogênio (BET/BJH), difração de raios-X (DRX), análise química elementar (CHN), espectroscopia de infravermelho com transformada de Fourier (FTIR), microscopia eletrônica de varredura (MEV) e termogravimetria (TG/DTG). A análise elementar indicou que 0,341 mmol/g de 1,2-dicloroetano e 0,095 mmol/g de salen foi ancorado na superfície da sílica, que apresentou estabilidade térmica até 209°C e área de superfície específica de 106,4 m²/g. Foi realizado um estudo sobre a capacidade de adsorção de íons cádmio (II) pela sílica modificada e não modificada. Os resultados indicam a superior capacidade de adsorção de cádmio pela sílica modificada, em soluções com baixa concentração do íon. / This thesis presents the obtainment of silica xerogel by rice husk charcoal and its surface modification using an organic ligand type Schiff-base. The purpose of this agro-industrial residue utilization is the production of an adsorbent capable to remove heavy metals present in contaminated waters. The silica contained in the biomass was obtained by alkaline extraction in sodium silicate with hydrolysis through sol-gel process, and modified with salen, using 1,2-dichloroethane as bi-functional spacer. The modified xerogel silica was evaluated through analysis of nitrogen adsorption/desorption isotherms (BET/BJH), X-ray diffraction (XRD), chemical elementary analysis (CHN), Fourier transform infrared spectroscopy (FTIR), scanning electronic microscopy (SEM) and thermogravimetric analysis (TG/DTG). The elementary analysis pointed that 0,341mmol/g of the 1,2-dichloroethane and 0,095mmol/g of the salen was anchored to the silica surface, that presented thermal stability until 209°C and specific surface area of 106,4 m²/g. An evaluation about the ion cadmium II adsorption capacity of the silica modified and unmodified was performed. The results pointed to the superior cadmium adsorption capacity for the modified silica if low ion concentration solutions.

Cette thèse est consacrée à la synthèse de complexes 3d homo et hétérométalliques avec des ligands bases de Schiff ou dérivés de la 1,2,4,5-tétrazine, à l’investigation de leur structure et de leurs propriétés physico-chimiques. Ce travail peut être divisé en trois parties. Dans la première partie, nous nous sommes principalement concentrés sur les ligands bases de Schiff, dérivés du salicylaldéhyde et des aminoalcools, formés in situ. Treize complexes hétérométalliques ont été obtenus et entièrement caractérisés. Il a été montré que les composés synthétisés possèdent une activité catalytique dans la réaction de l’oxydation photochimique de l’eau, présentent des propriétés de photoconductive dans les polymères composites et peuvent être utilisés pour le développement de matériaux multifonctionnels. La deuxième partie décrit la fonctionnalisation des ligands base de Schiff par l’introduction dans leur structure des unités tétrathiafulvalène et métaux dithiolènes électroactives. Deux nouvelles familles de ligands ont été synthétisées et caractérisées. La série de sels de radicaux cations et de complexes dithiolènes homo et hétérométalliques ainsi que leurs propriétés physiques ont été discutées. La dernière partie est consacrée aux ligands à base de tétrazine. Les principaux avantages du noyau tétrazine ont été discutés. Deux nouveaux ligands dérivés de la picolylamine et leurs complexes 3d mono- et binucléaires ont été décrits. / The thesis is devoted to the synthesis of homo- and heterometallic 3d-metal complexes with Schiff base ligands or derivatives of 1,2,4,5- tetrazine, together with the investigation of their structural and physico-chemical properties. This work can be divided in three parts. In the first part we have been mainly focused on the Schiff base ligands, derivatives of the salicylaldehyde and aminoalcohols. Thirteen heterometallic complexes were obtained and fully characterized. It has been shown that the synthesized compounds possess catalytic activity in the photochemical water oxidation, exhibit photoconducting properties in polymeric composites and can be used for the development of multifunctional materials of wide use. The second part describes the functionalization of Schiff base ligands by the introduction into their structure of electroactive tetrathiafulvalene and dithiolate moieties. Two new families of ligands were synthesized and characterized. The series of radicalcation salts and homo- and heterometallic dithiolene complexes together with the investigation of their physical properties have been described. The last part is devoted to the tetrazine based ligands. The main advantages of the tetrazine ring have been discussed. Two new ligands, derivative of picolylamine and their mono- and binuclear 3d-metal complexes are reported. In conclusion, perspectives of further research related to the described results were highlighted.

Nos últimos anos, têm-se notado o aumento do número de pesquisas relacionadas aos complexos de metais de transição com base de Schiff devido a suas interessantes estruturas e amplas aplicações, isso se deve em parte a formação de complexos estáveis, apresentando um papel importante na química de coordenação. A determinação estrutural dos átomos nas moléculas é necessária para que suas propriedades químicas, físicas e biológicas possam ser compreendidas. Para esta finalidade, existe uma grande variedade de técnicas químicas e físicas, na qual podemos citar a Difração de Raios X. Os avanços computacionais dos últimos anos e sua agregação na ciência, proporcionou um crescimento nas pesquisas que utilizam métodos teóricos, pois possibilitou sua aplicação em diversas áreas que dependiam de tão evolução para continuação de seus estudos. Vale ressaltar, que o uso de cálculo teórico têm apresentado um grande interesse pelos pesquisadores da área da Química, seja para a compreensão das suas estruturas ou para o estudo dos mecanismos de reações. Logo, o objetivo desse trabalho é a investigação estrutural de bases de Schiff, através da determinação das estruturas cristalinas por difração de raios-X. A partir dos dados cristalográficos foram avaliados parâmetros geométricos, interações intermoleculares, onde ambos os dados foram comparados com os da literatura obtendo resultados satisfatórios. A estrutura ASZ, apresentou estrutura semelhante com a esperada, obtendo-se índices de discordância R = 0,0774, wR2 = 0,2302, o que caracteriza um refinamento eficiente. A molécula possui um eixo cristalográfico de ordem 2 e grupo pontual 2/m. O complexo Zn(apy-epy), obteve bons índices de discordância R = 0,0621, wR2 = 0,2172, centrossimétrica, apresentando grupo pontual mmm com eixo de ordem 2. O átomo central de zinco tem geometria bipiramidal ligada a 6 átomos de nitrogênio. O ligante CW2-10A, foi a estrutura que obteve o melhor valor de discordância R = 0,0348, wR2 = 0,0902 e grupo pontual 2/m. A estrutura determinada, estava de acordo com o esperado. A estrutura final do complexo com sigla CuDenim, estava de acordo com o proposto, com um índice de discordância satisfatório R = 0,0746, wR2 = 0,2122, também apresentou uma interação do metal Cu com átomos de oxigênio do íon perclorato. O complexo CW1-53A, possui alguns átomos desordenados e foi preciso que fossem refinados isotropicamente, apresentou índices de discordância dentro do ideal R = 0,0436, wR2 = 0,1227. Os cálculos de frequência vibracional não identificaram frequências imaginárias para nenhuma das estruturas otimizadas. A estabilidade química foi explicada pelo gap HOMO-LUMO, bem como os locais de interações intermoleculares foram explicados através dos mapas de superfície Hirshfeld e pelo mapa de potencial eletrostático. / In recent years, has been an increase in studies related with Schiff-bases transition metal complexes due to their interesting structures and wide applications. One reason for this is the formation of stable complexes, presenting an important role in coordination chemistry. The structural determination of the atoms in the molecules is necessary in understanding in their chemical, physical and biological properties. For this purpose, there is a great variety of chemical and physical techniques, in which we can mention X-ray Diffraction. The computational advances of the last years and their aggregation in science, provided to growth in the researches that use theoretical methods, as it allowed its application in several areas that depended on so to continue their studies. It is worth mentioning that the use of theoretical calculus has shown a great interest by researchers in the field of Chemistry, either to understand their structures or to study the mechanisms of reactions. Therefore, the objective of this work is the structural investigation of Schiff bases, through the determination of the crystalline structures by X-ray diffraction. Where all the structures presented good indexes of disagreement and the obtained structures were within the expected one. From the crystallographic data, geometric parameters, intermolecular interactions were evaluated, and both data were compared with those of the literature, obtaining satisfactory results. The structure ASZ, presented similar to the one expected, with discordance indices R = 0,0774, wR2 = 0.2302, therefore characterizing the refinement. The molecule has a crystallographic axis of order 2 and a point group 2 / m. The complex Zn (apy-epy), obtained good discordance indices R = 0.0621, wR2 = 0.2172, centrossimetric, presenting a point group mmm with axis of order 2. The central zinc atom has bipyramidal geometry attached to 6 nitrogen atoms. The ligand CW2-10A was the structure that obtained the best discordance value R = 0.0348, wR2 = 0.0902 and 2/m point group. The structure determined was as expected. The final structure of the complex with CuDenim acronym, was in agreement with the with satisfactory discordance index R = 0.0746, wR2 = 0.2122, also presented a Cu metal interaction with oxygen atoms of the perchlorate ion. The complex CW1-53A, has some disordered atoms and had to be refined isotropically. It presented disagreement indices within the ideal R = 0.0436, wR2 = 0.1277. The vibrational frequency calculations did not identify imaginary frequencies for any of the optimized structures. The chemical stability was explained by the HOMO-LUMO gap, as well as the sites of intermolecular interactions were explained through the Hirshfeld surface maps and the electrostatic potential map.

Nos últimos anos, têm-se notado o aumento do número de pesquisas relacionadas aos complexos de metais de transição com base de Schiff devido a suas interessantes estruturas e amplas aplicações, isso se deve em parte a formação de complexos estáveis, apresentando um papel importante na química de coordenação. A determinação estrutural dos átomos nas moléculas é necessária para que suas propriedades químicas, físicas e biológicas possam ser compreendidas. Para esta finalidade, existe uma grande variedade de técnicas químicas e físicas, na qual podemos citar a Difração de Raios X. Os avanços computacionais dos últimos anos e sua agregação na ciência, proporcionou um crescimento nas pesquisas que utilizam métodos teóricos, pois possibilitou sua aplicação em diversas áreas que dependiam de tão evolução para continuação de seus estudos. Vale ressaltar, que o uso de cálculo teórico têm apresentado um grande interesse pelos pesquisadores da área da Química, seja para a compreensão das suas estruturas ou para o estudo dos mecanismos de reações. Logo, o objetivo desse trabalho é a investigação estrutural de bases de Schiff, através da determinação das estruturas cristalinas por difração de raios-X. A partir dos dados cristalográficos foram avaliados parâmetros geométricos, interações intermoleculares, onde ambos os dados foram comparados com os da literatura obtendo resultados satisfatórios. A estrutura ASZ, apresentou estrutura semelhante com a esperada, obtendo-se índices de discordância R = 0,0774, wR2 = 0,2302, o que caracteriza um refinamento eficiente. A molécula possui um eixo cristalográfico de ordem 2 e grupo pontual 2/m. O complexo Zn(apy-epy), obteve bons índices de discordância R = 0,0621, wR2 = 0,2172, centrossimétrica, apresentando grupo pontual mmm com eixo de ordem 2. O átomo central de zinco tem geometria bipiramidal ligada a 6 átomos de nitrogênio. O ligante CW2-10A, foi a estrutura que obteve o melhor valor de discordância R = 0,0348, wR2 = 0,0902 e grupo pontual 2/m. A estrutura determinada, estava de acordo com o esperado. A estrutura final do complexo com sigla CuDenim, estava de acordo com o proposto, com um índice de discordância satisfatório R = 0,0746, wR2 = 0,2122, também apresentou uma interação do metal Cu com átomos de oxigênio do íon perclorato. O complexo CW1-53A, possui alguns átomos desordenados e foi preciso que fossem refinados isotropicamente, apresentou índices de discordância dentro do ideal R = 0,0436, wR2 = 0,1227. Os cálculos de frequência vibracional não identificaram frequências imaginárias para nenhuma das estruturas otimizadas. A estabilidade química foi explicada pelo gap HOMO-LUMO, bem como os locais de interações intermoleculares foram explicados através dos mapas de superfície Hirshfeld e pelo mapa de potencial eletrostático. / In recent years, has been an increase in studies related with Schiff-bases transition metal complexes due to their interesting structures and wide applications. One reason for this is the formation of stable complexes, presenting an important role in coordination chemistry. The structural determination of the atoms in the molecules is necessary in understanding in their chemical, physical and biological properties. For this purpose, there is a great variety of chemical and physical techniques, in which we can mention X-ray Diffraction. The computational advances of the last years and their aggregation in science, provided to growth in the researches that use theoretical methods, as it allowed its application in several areas that depended on so to continue their studies. It is worth mentioning that the use of theoretical calculus has shown a great interest by researchers in the field of Chemistry, either to understand their structures or to study the mechanisms of reactions. Therefore, the objective of this work is the structural investigation of Schiff bases, through the determination of the crystalline structures by X-ray diffraction. Where all the structures presented good indexes of disagreement and the obtained structures were within the expected one. From the crystallographic data, geometric parameters, intermolecular interactions were evaluated, and both data were compared with those of the literature, obtaining satisfactory results. The structure ASZ, presented similar to the one expected, with discordance indices R = 0,0774, wR2 = 0.2302, therefore characterizing the refinement. The molecule has a crystallographic axis of order 2 and a point group 2 / m. The complex Zn (apy-epy), obtained good discordance indices R = 0.0621, wR2 = 0.2172, centrossimetric, presenting a point group mmm with axis of order 2. The central zinc atom has bipyramidal geometry attached to 6 nitrogen atoms. The ligand CW2-10A was the structure that obtained the best discordance value R = 0.0348, wR2 = 0.0902 and 2/m point group. The structure determined was as expected. The final structure of the complex with CuDenim acronym, was in agreement with the with satisfactory discordance index R = 0.0746, wR2 = 0.2122, also presented a Cu metal interaction with oxygen atoms of the perchlorate ion. The complex CW1-53A, has some disordered atoms and had to be refined isotropically. It presented disagreement indices within the ideal R = 0.0436, wR2 = 0.1277. The vibrational frequency calculations did not identify imaginary frequencies for any of the optimized structures. The chemical stability was explained by the HOMO-LUMO gap, as well as the sites of intermolecular interactions were explained through the Hirshfeld surface maps and the electrostatic potential map.