Synthesis of inorganic biomimetics of the FeMo cofactor of Nitrogenase enzyme.
Molybdenum is a transition metal that has an important role in nature due to its high affinity to oxygen and sulfur atoms. It is found in the enzyme nitrogenase responsible of the reduction of atmospheric nitrogen to make it bio-available, such process is very important for the assimilation of nitro...
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| Формат: | bachelorThesis |
| Язык: | eng |
| Опубликовано: |
2020
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| Предметы: | |
| Online-ссылка: | http://repositorio.yachaytech.edu.ec/handle/123456789/154 |
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Добавить метку | Итог: | Molybdenum is a transition metal that has an important role in nature due to its high affinity to oxygen and sulfur atoms. It is found in the enzyme nitrogenase responsible of the reduction of atmospheric nitrogen to make it bio-available, such process is very important for the assimilation of nitrogen by plants and a lot of research is made trying to mimic nitrogenase activity. Schrok and Yandulov synthetized a functional catalyst with high efficiency (~66%) and it served to inspire the research on inorganic mimetics. Thus, the main goal of this study is to obtain an inorganic mimetic of the nitrogenase of molybdenum VI and III complex with a polynitrogenated ligand as L1= 1,9-bis(2’-pyridyl)-2,5,8-triazonane (picdien). In the first part of the work, Mo(acac)3 and L1•3HCl were synthesized to later get the [Mo(III)-picdien] compound that corresponds to a yellow-brown powder confirmed by UV-vis and cyclic voltammetry. In this reaction, it was possible to realize that the reaction is sensible to produce molybdenum oxides or oxo groups being the last one the most important. Therefore, this tends to produce Mo-oxo groups invited us to understand the oxygen atom transfer (OAT) reactions involved in the oxidation of organic substrates mainly. Then, the Mo(VI) complexes were obtained with a mixture of MoO2(acac)2 with L1•3HCl, but it was employed different solvents to obtain different products. In the mixture of THF and ethanol a dark green powder was obtained, the use of ethanol gives a yellow fine powder and the use of methanol with NaTPB to precipitate a white fine powder. It was not possible to get a single crystal of any of these compounds but were characterized with elemental analysis, IR, NMR, EPR, UV-Vis and magnetic susceptibility. It was found that all these products were diamagnetic (d0 or d2) but they are EPR active because there are radical species of metal and ligand as side products of OAT or oxidative dehydrogenation (OD) reactions. The nature of radicals depends on the solvent employed. The OAT reactions change the oxidation state of metal by two units for the movement of each oxygen atom (metal-centered) and promote the formation of µ-oxo complexes and different oxygen species seen by its Mo-O stretching (IR). The reactivity of ligand L1 depends on the metal that participates in the OD responsible to oxidize an amine to an imine and reduce the metal by one unit. There was not enough information to support the reaction that predominates. Thus, different isomers and changes in the denticity of ligand forced us to propose structures based on the studies of elemental analysis, IR and EPR. |
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