Theoretical Investigation On The Charge Transport Properties Of Organic Macromolecular Coordination With Fe\Cu\Al Metal

Extracellular respiration is a novel microbial metabolism, which means Extracellular respiratory bacteria Oxidation of its material in the cell and release electron under the condition of anaerobic environment, At the same time the released electron was passed to the extracellular-electron acceptor through intracellular respiration chain, In the process to produce energy to sustain its extracellular respiratory bacteria growth. The extracellular respiratory theory changed on traditional knowledge of microbes transferred electron and interact with micro interface environment. The more widely existing research for microorganisms extracellular respiratory mainly have two types: Fe breathing and humus breathing. Its core scientific problems are for the extracellular electron transfer process. People widespread concerning right now is how to improve the electron transfer efficiency in the process of extracellular respiratory for microbe, thereby using extracellular respiratory research develop microbial fuel cells effectively and organic pollutants degradation methods. In the process of Fe breathing, Cytochrome(c-Cyts) is the main part of the electron transport chain, In the process of extracellular respiratory constantly accept and release electrons. Generating energy maintain extracellular respiratory bacteria growth. Research found that in the center of the c-Cyts element Fe axial coordination with different strong electron-withdrawing base such as imidazole and 2-methyl imidazole can effectively control the electron transfer efficiency for Fe breath. In the process of humus breathing, humic acid lha, as a kind of organic molecules is a key component of extracellular electron acceptor. Experimental study has found that humic acid molecular ligand with different metal elements(Fe, Cu, Al) have different ability to accept electronic, which decides the extracellular humus respiratory electron transfer efficiency in the process of breathing. Which determine the electron transfer efficiency of extracellular humus respiratory in the process of breathing? It is a pity that the existing test methods and research methods are not able to cognition microorganisms’ extracellular breathing of two main ways for microcosmic mechanism and the mechanism of electron transfer from the angle of the atomic and molecular. This research from the perspective of the theory of computational chemistry, take a study on the relationship between molecular structure and the electron transfer efficiency, for the two kinds of organic molecules Cytochrome c and humic acid coordination with metal elements(Fe, Cu, Al). Study the stability of the two kinds of organic macromolecular ligand complexation with metal and electron transfer mechanism. The Concrete research content is as follows:Fe breathing: The charge transport properties and stability of imidazoles which axial coordinate to protoheme molecules, has been investigated by density functional theory(DFT) using Becke’s three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal correlation functional(B3LYP). The geometries of protoheme molecule and the complex compounds were optimized in gaseous phase at the 6-31+G(d) level. In view of energy of each compound analyzed, We find that all heme Fe3+ and Fe2+ complex compound were axial coordinate with imidazoles by strong field and low spin state. Meanwhile binding energies were calculated, the structure feature and the frontier orbital distribution of complex compounds were analyzed. On the basis of Marcus theory, the reorganization energy, matrix element and the charge transport rate constants were calculated. The results showed that the charge transport rate of the complex compound coordinated imidazole is bigger than that of the complex compound coordinated 2-methyl imidazole, Which indicated that the charge transfer between imidazole and Heme iron is more beneficial than the 2-methyl imidazole coordinate to Heme iron, Our result is in accordance with the experimental result.Humus Breathing: The best complexation sites, The most stable state spin of the complex and the electron transfer ability. Has been investigated by density functional theory(DFT) using Becke’s three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal correlation functional(B3LYP). The stable geometries structure of the complex, the frontier orbital distribution energy gap of the complex compounds, the electronic reorganization energy and charge transfer rate were research in gaseous phase at the 6-31+G(d) level(Fe, Cu, Al with lanl2 dz basis). Discuss three kinds of metal effects on humic acid breath charge transfer. The complex configuration of humic acid molecules ligand with different metal and the same metal ligand with a humic acid molecule in different sites were optimized at the 6-31 G level. Results show that in the d position three metals can have lower coordination complex energy. Through the analysis of the energy, three kinds of metal Fe3+ and Fe2+,Al3+ and Al2+,Cu2+ and Cu+ are in strong field and low spin states were stable. At the same time calculated the binding energy, analysis the characteristics of the complex structure and the frontier orbital distribution. On the basis of Marcus theory, the reorganization energy, matrix element and the charge transport rate constants were calculated. Found that the order of the charge transfer rate is Fe>Cu>Al, Our result is in accordance with the experimental result.