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Over the last few decades, Porous Coordination Polymers (PCPs, a.k.a. MOFs) have been extensively studied for a number of applications due to their functional and structural versatility. Nonetheless, systematic studies that explore the structure-function relationship of frameworks decorated with different functional groups remain limited. In the present work, two families of coordination polymers that contain organophosphine building blocks have been synthesized and characterized. These materials contain a periodic array of P(III) Lewis base sites that are available for post-synthetic functionalization. PCM-10 is a porous coordination polymer based on Ca(II) and tris(p-carboxylated) triphenylphosphine. The material displayed a 3-dimensional surface, ideal for a series of post-synthetic modifications. The versatility of P(III)→P(V) chemistry allowed for decoration of the R₃P: sites of PCM-10 with different functional groups. Solid-state treatment of the framework with a variety of precursors, gave rise to a family of isostructural materials (ClAu-PCM-10, O=PCM-10 and (Me‒PCM-10)X; X = I⁻, F⁻, BF₄⁻ and PF₆⁻). These post-synthetic modifications directly affected the host-guest interactions, as demonstrated by comparative adsorption studied of CO₂, H₂ and other small molecules. For example, the phosphonium (Me-PCM-10)X composites displayed broad tunability of isosteric heats of CO₂ adsorption, depending on the counter-ion. Similarly, the ClAu-PCM-10 derivative resulted in selective adsorption of 1-hexene vs. n-hexane and displayed significantly increased H₂ uptake capacity, when compared to PCM-10. Ln-PCM-22 is a family of isostructural PCPs based on tris(p-carboxylated) triphenylphosphine and Ln(III) (Ln = Sm-Yb). Photoluminescence studies of Eu-PCM-22 and Tb-PCM-22 were used to elucidate certain aspects of the solid-state emissive properties of phosphine-based materials. In addition, a single-crystal-to-single-crystal post-synthetic oxidation of Tb-PCM-22 was achieved to yield the composite material Tb-O=PCM-22. This modification resulted in enhancement of the quantum efficiency, compared to that of the parent framework. These results will help further the understanding of PCMs and direct the upcoming synthesis and application of these materials. / text

This study investigates the metallosupramolecular chemistry of functionalised 1,2-diazole ligands, by the preparation and characterisation of a range of first-row transition metal coordination polymers and discrete assemblies. To this end, twenty-six ligands containing 1,2-diazole functionality have been synthesised, twenty-one of which have not previously appeared in the coordination chemistry literature. Utilising these compounds, forty new coordination compounds have been prepared and characterised by single-crystal X-ray crystallography and other analytical techniques, and their solid-state structural features discussed in the search for reproducible new diazole-based synthons for the designed synthesis of new functional materials. Particular attention is paid to the contribution of the second nitrogen atom on the diazole ring, which participates in structure-directing hydrogen bonding interactions, or acts as a synthetic handle to easily append further functionality to the ligand system. The design of the ligands is separated into two primary categories, representing the different approaches adopted for the synthesis of the metallosupramolecular architectures. The combination of 1H-pyrazole and carboxylic acid functionality in mixed-ligand assemblies was investigated with the combination of bis-pyrazole and bis-carboxylic acid ligands, and with the preparation of ligands containing both functional groups. This approach was extended to the related heterocyclic species indazole, with all five possible isomers of indazole-carboxylic acid synthesised and used in coordination chemistry for the first time. The 1H-diazole-carboxylate synthon was employed in the synthesis of fourteen coordination polymers and three discrete assemblies. Heteroaryl substitution at the 1-position of pyrazole or indazole compounds was employed to generate chelating ligands containing pyridine or benzimidazole functionality, which were used to form nineteen discrete complexes, including dinuclear helicates and metallocycles, and five coordination polymers. The effect of flexibility and distance between coordination sites in bis-bidentate ligand systems was examined, in conjunction with studies into the effect of steric bulk and variation of the electronic nature of the coordinating groups. While this study is primarily concerned with the solid-state structural chemistry of 1,2-diazole coordination compounds, attention is paid where appropriate to solution-based measurements such as NMR and UV/Visible studies, and the pertinent behaviour of functional materials, such as thermogravimetric analysis for solvated species and gas uptake studies for stable void-containing materials.

Metal-organic frameworks (or coordination polymers) are a recently-identified class of porous polymeric materials, consisting of metal ions or clusters linked together by organic bridging ligands. The major advantage of MOFs over other traditional materials, such as zeolites or activated carbons, is that their synthesis methods have provided an extensive class of crystalline materials with high stability, tunable metrics, and organic functionality. The ability to modify the physical environment of the pores and cavities within MOFs allow tuning of the interactions with guest species, and serves as a route to tailor the chemical stability and/or reactivity of the frameworks for specific applications. The classical way to incorporate functional groups into a MOF is the modification of the organic precursor with specific substituents before synthesizing the MOF itself; we call this approach pre-functionalization method. Functionalization of organic precursors is the initial and necessary step to obtaining functionalized isostructural MOFs and also provides the possibility for the post-synthetic modification of MOFs. However, in some cases, the functional groups may interfere with MOF synthesis and alter the topology of desired MOF. The goal of this proposed research is to explore the possibilities of metal-organic frameworks (MOFs) as novel porous structures, to study the effect of functional groups on the topologies and adsorption behavior of MOFs, and to understand how the synthesis conditions affect the phase purity and the in-situ reaction of ligands.

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The synthesis and properties of novel Metal Organic Frameworks were investigated and reported in this thesis. Thirteen new materials have been synthesized and their properties have been discussed with nine of the structures being solved. The most interesting and useful MOF among the thirteen materials is STAM-1, a copper-based Metal Organic Framework in which the starting linker (Benzene-1,3,5-tricarboxylic acid) undergoes selective in situ monoesterification during the synthesis. The monoesterified BTC can be recovered easily from the MOF, opening up MOF synthesis as a “protection” tool for unexpected selectivity in preparative chemistry that is difficult to accomplish using standard organic chemistry approaches. The selective linker derivatisation leads to the formation of a porous MOF with two types of accessible channel; one hydrophilic lined by copper and the other hydrophobic, lined by the ester groups. The unique structure of the pores leads to unprecedented adsorption behaviour, which reacts differently to gases or vapours of dissimilar chemistry and allows them to access different parts of the structure. The structural flexibility of STAM-1 shows significant differences in the kinetics of O₂ and N₂ adsorption, showing potential for new materials to be developed for air separation. Having two types of channel systems, adsorption can be switched between the two channels by judicious choice of the conditions; a thermal trigger to open the hydrophilic channel and a chemical trigger to open the hydrophobic channel. The storage and release capability of NO in STAM-1 was investigated for use in biomedical applications. Successful studies showed the strength of the antibacterial effects of NO loaded STAM-1, by using three different bacterial strains as a test of performance and were found to be bactericidal. Furthermore the antibacterial effects of NO free STAM-1 were also probed and found to be bactericidal even with low concentrations of the material such as 5 wt%. STAM-1 showed some complex magnetic behaviour by displaying strong antiferromagnetic properties at room temperature and ferromagnetic properties at lower temperatures. The antiferromagnetic coupling was observed within the dimer and ferromagnetic coupling between the dimers. This property of ferromagnetism can only be attributed to the corporation of magnetic dimers in the framework. STAM-2 displays a different magnetic behaviour than STAM-1 which shows paramagnetic properties at room temperature and antiferromagnetic properties at lower temperatures. Other novel MOFs were also successfully characterised and their properties were investigated for potential applications.

Este trabalho descreve a síntese e caracterização de polímeros de coordenação (PC) e sua aplicação como fotocatalisadores heterogêneos ativos sob a radiação visível, visando a degradação de compostos orgânicos em água. Problemas ambientais têm ocupado posição de destaque na sociedade contemporânea. Dentre eles, o uso de combustíveis fósseis e a remoção de compostos poluentes do meio ambiente têm merecido especial atenção. Uma das alternativas mais indicadas como substituinte dos combustíveis fósseis é a energia solar, por ser limpa, renovável e presente em todo o planeta. O estudo de materiais fotoativos é essencial para aproveitar ao máximo essa fonte. A fotocatálise é um processo que utiliza a energia luminosa para realizar reações químicas. Os PC têm mostrado ótimos resultados na área. Esses são compostos poliméricos cujos monômeros são unidades de coordenação. Neste trabalho foram sintetizados PC formados por diferentes metais de transição e ligantes orgânicos. Dentre eles destacam-se níquel e benzenodicarboxilato (Ni-BDC). Os materiais foram caracterizados por FTIR, DRX, adsorção-dessorção de N2, DRS, TGA, MEV e ICP-OES. Os resultados sugerem a formação de PC inéditos, dotados de sítios de coordenação insaturados, com boa estabilidade térmica, porém com estabilidade em meio aquoso inferior. O ensaio de degradação fotocatalítica de corante evidencia que os materiais são fotoativos na luz visível, apesar da descoloração não ser completa. Este resultado é interessante, pois polímeros de coordenação de níquel ainda são pouco estudados como fotocatalisadores, e esse é um metal barato e abundante. / This work describes the synthesis and characterization of coordination polymers (CP) and their application as heterogeneous photocatalysts, under visible radiation, in degradation of organic compounds in water. Environmental issues have taken prominent position in contemporary society. Among them, fossil fuel usage and removal of hazardous compounds deserve special attention. One of the best alternatives to replace fossil fuels is the solar power, which is clean, renewable and ubiquitous throughout the planet. Research on photoactive materials is essential to improve this energy source use. Heterogeneous photocatalysis process uses light energy to induce chemical reactions. CP are exhibiting remarkable results in the field. These are polymeric compounds with coordination units as monomers. In the present work, CP based on different transition metals and organic ligands were synthesized, such as nickel benzenedicarboxylate (Ni-BDC). The materials were characterized by FTIR, XRD, N2 adsorption-desorption, DRS, TGA, SEM and ICPOES. The results suggest the formation of novel CP, endowed with unsaturated metal sites and good thermal stability, however with low stability in aqueous medium. The photocatalytic dye degradation experiments indicate the materials are photoactive under visible light, although the discoloration was not complete. This is an interesting result, considering that the research on nickel coordination polymers as photocatalysts is still scarce.

Este trabalho descreve a síntese e caracterização de polímeros de coordenação (PC) e sua aplicação como fotocatalisadores heterogêneos ativos sob a radiação visível, visando a degradação de compostos orgânicos em água. Problemas ambientais têm ocupado posição de destaque na sociedade contemporânea. Dentre eles, o uso de combustíveis fósseis e a remoção de compostos poluentes do meio ambiente têm merecido especial atenção. Uma das alternativas mais indicadas como substituinte dos combustíveis fósseis é a energia solar, por ser limpa, renovável e presente em todo o planeta. O estudo de materiais fotoativos é essencial para aproveitar ao máximo essa fonte. A fotocatálise é um processo que utiliza a energia luminosa para realizar reações químicas. Os PC têm mostrado ótimos resultados na área. Esses são compostos poliméricos cujos monômeros são unidades de coordenação. Neste trabalho foram sintetizados PC formados por diferentes metais de transição e ligantes orgânicos. Dentre eles destacam-se níquel e benzenodicarboxilato (Ni-BDC). Os materiais foram caracterizados por FTIR, DRX, adsorção-dessorção de N2, DRS, TGA, MEV e ICP-OES. Os resultados sugerem a formação de PC inéditos, dotados de sítios de coordenação insaturados, com boa estabilidade térmica, porém com estabilidade em meio aquoso inferior. O ensaio de degradação fotocatalítica de corante evidencia que os materiais são fotoativos na luz visível, apesar da descoloração não ser completa. Este resultado é interessante, pois polímeros de coordenação de níquel ainda são pouco estudados como fotocatalisadores, e esse é um metal barato e abundante. / This work describes the synthesis and characterization of coordination polymers (CP) and their application as heterogeneous photocatalysts, under visible radiation, in degradation of organic compounds in water. Environmental issues have taken prominent position in contemporary society. Among them, fossil fuel usage and removal of hazardous compounds deserve special attention. One of the best alternatives to replace fossil fuels is the solar power, which is clean, renewable and ubiquitous throughout the planet. Research on photoactive materials is essential to improve this energy source use. Heterogeneous photocatalysis process uses light energy to induce chemical reactions. CP are exhibiting remarkable results in the field. These are polymeric compounds with coordination units as monomers. In the present work, CP based on different transition metals and organic ligands were synthesized, such as nickel benzenedicarboxylate (Ni-BDC). The materials were characterized by FTIR, XRD, N2 adsorption-desorption, DRS, TGA, SEM and ICPOES. The results suggest the formation of novel CP, endowed with unsaturated metal sites and good thermal stability, however with low stability in aqueous medium. The photocatalytic dye degradation experiments indicate the materials are photoactive under visible light, although the discoloration was not complete. This is an interesting result, considering that the research on nickel coordination polymers as photocatalysts is still scarce.

Uranyl hybrid materials attract interest owing to promise of synthesizing functional materials, but typically experience limitations in extending dimensionality. This is due to the tendency of the uranyl cation to oligomerize along its equatorial plane, leading to the formation of flat secondary building units. One way to overcome these limitations is to utilize weak interactions to hold a structure together. This can be achieved through using ligands to build secondary building units through strong coordinative bonds that simultaneously provide supramolecular interactions as a means to extend dimensionality in the structure. We examined amino acids as a ligand choice because of its dual features of having a carboxyl group for coordination to the uranyl cation and an amino group that can be protonated to provide charge-assisted hydrogen bonding between to secondary building units in the structure. Aqueous benchtop chemistry in ambient conditions were used to synthesize and crystallize thirteen uranyl-glycine coordination compounds whose structures were elucidated with single crystal X-ray diffraction. Under these conditions, 1D coordination polymers form. The structural features in these compounds were varied to investigate their effects on the hydrogen bonding, including the presence/absence of metal center hydrolysis, the presence of other H-bond accepting carboxylate ligands, the use of dicarboxylic acid ligands to connect uranyl centers, and the addition of a secondary metal. The compounds provide insight into how the charge-assisted hydrogen bonding provided by zwitterionic amino acids is a viable means to extending the dimensionality of uranyl hybrid materials in a variety of chemical systems.

Made available in DSpace on 2014-06-11T19:29:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-02-28Bitstream added on 2014-06-13T18:58:39Z : No. of bitstreams: 1 bego_am_me_araiq.pdf: 727479 bytes, checksum: 6c9853bf50bed40f27eb036856b0e400 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O 1,2,4-triazol é um composto heterocíclico aromático contendo três átomos de nitrogênio dispostos nas posições 1, 2 e 4 de um anel de cinco membros. O interesse nos complexos contendo este ligante iniciou-se em meados de 1965, quando as propriedades magnéticas de vários sistemas triazólicos foram estudadas. Comparado aos pirazóis e imidazóis, o 1,2,4-triazol apresenta um átomo de nitrogênio a mais, o que lhe confere uma maior diversidade de modos de coordenação. Este trabalho contemplou inicialmente a síntese, a caracterização espectroscópica e o estudo do comportamento térmico de complexos de Pd(II) contendo o ligante 1,2,4-triazol. Ênfase foi dada à investigação da influência de diversas rotas sintéticas no tipo de complexo formado. As metodologias gerais de síntese dos complexos envolveram preferencialmente a reação de substituição da acetonitrila na esfera de coordenação do precursor [PdCl2(MeCN)2] pelos ligantes 1,2,4-triazol (Htrz) e trifenilfosfina (PPh3) e a utilização do complexo [H2PdCl4] como precursor alternativo. Quando foi utilizada a razão molar 1 [PdCl2(MeCN)2] : 2Htrz : 2 PPh3 houve apenas a formação do complexo mononuclear [PdCl2(PPh3)2], não sendo observada portanto a coordenação do triazol. No entanto, com a proporção molar 1[PdCl2(MeCN)2] : 2Htrz: 1 PPh3, em uma condição experimental de excesso de triazol, a coordenação deste ligante foi favorecida, gerando o complexo trinuclear [Pd3Cl4(trz)2(PPh3)3] com o ânion triazolato coordenado nos modos bi e tridentado. Durante a coordenação, o triazol é facilmente desprotonado, o que privilegia a coordenação do ânion triazolato, resultando em complexos onde o mesmo pode atuar nos modos bi e/ou tridentado. Entretanto, isto pode ser evitado acidificando o meio reacional. / 1,2,4-triazole is an aromatic heterocyclic compound bearing three nitrogen atoms in the 1,2,4 positions of a five-membered ring. The interest on their complexes has begun in 1965 when magnetic properties of some 1,2,4-triazolyl systems were studied. The fact that 1,2,4-triazole possesses an additional nitrogen atom, when compared to pyrazoles and imidazoles, confers a wide variety of coordination modes. This work has dealt with the synthesis, spectroscopic characterization, and the study of thermal behavior of Pd(II) compounds containing the 1,2,4-triazole ligand. The influence of the synthetic route on the resulting complexes was investigated. The general synthetical procedure involved the displacement of acetonitrile from the coordination sphere of [PdCl2(MeCN)2] precursor by the ligands 1,2,4-triazole (Htrz) and triphenylphosphine (PPh3) as well the use of [H2PdCl4] as an alternative precursor. The 1,2,4-triazole did not coordinate on employing the molar ratio 1 [PdCl2(MeCN)2] : 2Htrz : 2 PPh3, affording only the mononuclear [PdCl2(PPh3)2] compound. However, the coordination of 1,2,4-triazole was verified when the molar ratio 1 [PdCl2(MeCN)2] : 2Htrz: 1 PPh3 was used, yielding the trinuclear [Pd3Cl4(trz)2(PPh3)3] complex in which the triazolato anion acts as bidentate and tridentate ligand. 1,2,4-triazole is easily deprotonated which favours the bi- and tridentate coordination modes. Nevertheless, the deprotonation is avoided by acidifying the reaction media. Therefore, compounds of general formulae [PdCl2(Htrz)] with the 1,2,4-triazole ligand in the bidentate mode were obtained in acid media and, depending on the precursor employed, the bidentate fashion can be controlled.