Study On The Oxygenation Of The Cobalt Alaninend And The Application In Oxidative Degradation Of Lignin

Oxygen carriers are transition metal complexes that can reversibly bind dioxygen?O₂?.Given that natural oxygen carriers?in vivo?possess complex structures and easily lost,artificial oxygen carriers are often used as model complexes to study the mechanism of oxygenation in organisms.These artificial oxygen carriers have potential applications in separation and storage of O₂,artificial blood,catalytic oxidation of organic compounds,and DNA probe.Therefore,the study of artificial oxygen carrier is of great significance.Firstly,in this paper,L-alanine?Ala?–Co?II?complexes were selected as the basic materials.Four different types of nitrogen heterocyclic ligand,namely,imidazole?Im?,pyridine?Py?,piperidine?Pi?,and 2-methyl pyrazine?Pz?,were used to synthesize ternary complexes.The structures of these complexes are analogous to those of His–Co?II?and PyA–Co?II?complexes.The oxygenation property were characterized by UV–vis spectroscopy,oxygen electrode,IR,ESI-MS and theoretical calculation.In addition,theoretical simulation was used to study the mechanism of reversible oxygenation.Research results may provide a novel strategy to design and synthesize new model compounds as oxygen carriers.Secondly,All theoretical calculations were performed using GAUSSIAN 03W default criteria and the B3LYP function.The different complexes,oxygenated complexes,dinuclear oxygenated complexes properties of the two oxygen carriers?Ala?alanine?–Co?II?and Ala–Co?II?–Py?pyridine??were studied in this paper.Density functional theory?DFT?was used to study the changes of geometry structures,electrons structures,frontier molecular orbitals and aging mechanism during oxygenation process.For all calculations,the 6-31G*group was used for the C,H,N,O atoms of the organic ligand,and the LANL2DZ group was used for the center Co?II?,and the mixed group was used for the complex.And complete geometry optimization in GAUSSIAN 09 default standard.For all structures,DFT is used for frequency calculations to determine the nature of static points.Under each of the ground state geometries,TDDFT using the B3LYP function is performed for the calculation of the excited state.The solvent effect correction uses the CPCM mode.For the unoxygenated complexes and the oxygenated complexes,the multiplicity was calculated to be equal to 4?corresponding to a high spin state?and equal to 2?corresponding to a low spin state?,respectively.The resulting dioxygenated double-bridged bridges are formed by superoxide-type complexes,and their multiplicity may be singlet.Comparison of the geometrical configuration parameters and electronic properties of the two systems under different spin states reveals that there is a significant electron transfer between the metal Co?II?and the ligand.When the nitrogen heterocyclic ring is combined,the spin density shifts from the main dyz to the dz² track.The theoretical calculation shows that the oxygenation performance of Ala–Co?II?–Py system is higher than that of Ala–Co?II?system,and the axial ligand Py has an obvious influence on the oxygenation of the complex.Finaly,in this paper,With the depletion of fossil energy,the worldwide energy crisis and corresponding environmental problems have aroused extensive and in-depth research on biomass transformation.Lignin is one of the second abundant renewable polymers in the world today.It is a very promising work for its oxidation and degradation of value-added products.Lignin is a complex polymer compound,is a three-dimensional network structure of polymer by phenyl propane monomers with ether bonds and carbon carbon bond connection,by guaiacyl propane?G?,syringyl propane?S?,p-hydroxyphenyl propane?H?three structural unit random bonding.There are a variety of active functional groups and aromatic structural units,including methoxy,phenol hydroxyl group and methyl group.Through the method of catalytic oxidation degradation into highly functionalized monomer and oligomer products as the starting materials,other value-added products of degradation products:4-hydroxybenzaldehyde,vanillin,Ding Xiangquan and so on,these products use widely in the pharmaceutical,perfumery production,agricultural.There are two problems in Xinjiang paper industry,which are the source of pulp and the treatment of paper making black liquor,and it is also urgent to solve the problem of lignin oxidation degradation.The oxygen carrier model complexes of Ala–Co?II?–Im complexes as catalyst under hydrothermal conditions by catalyzed NaOH-H₂O₂oxidation of lignin to prepare aromatic compounds by UV/Vis absorption spectra,fluorescence spectra,thermogravimetric test,XPS and GC-MS.were used to characterize the product.Finally,under mild conditions,Ala–Co?II?-Im catalytic oxidation of lignin can significantly reduce the energy barrier of lignin main chemical bond cleavage,and achieve efficient depolymerization.This research is great significance in promoting the development of paper making industry,environmental governance and industrial catalysis in Xinjiang.The research results provide basic theories,methods and data support for the practical application of the technology and new materials.