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shinyman兑换贵宾
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那位大虾帮忙翻下摘要
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小弟我刚大三 专业文献还没看几篇，我们老师就让我们翻摘要，好多词不认识啊 金山也查不到，急人，麻烦哪位大虾帮忙，先谢谢了 Density functional theory calculations of the local spin densities of 3-substituted thiophenes and the oligomerization mechanism of 3-methylsulfanyl thiophene Abstract For obtaining a theoretical basis for the one-step formation of regioregular a-conjugated oligo- and polythiophenes, the electronic states of 3-substituted thiophenes and oligo(3-methylsulfanylthiophene)s were elucidated by molecular orbital calculations using density functional theory (DFT) with the Becke-type three parameters functionals (B3LYP) and the 6-31G(d) basis set. The reactivity for coupling reaction of mono- and oligo-thiophenes are inferred from the calculated unpaired electron spin densities of the respective radical cations, and the ionization potentials which correspond to the energies for generating radical cations during oxidative processes were estimated. The major regioselective products of the ligomerization of 3-(methylsulfanyl)thiophene [J. Org. Chem. 61 (1996) 8285] can be well understood in terms of the magnitude of spin densities. Since the steric hindrance between the methylsulfanyl side chains does not interfere with the coupling reaction occurring between 2-positions (C-2) of thiophene rings, the initiating reaction of 3-(methylsulfanyl)thiophene is the generation of a head-to-head (HH) dimer. On the other hand, the head-to-tail (HT) dimer would play an important role in the propagation reactions of 3-(4-butylphenyl)thiophene. This originates from the highest spin density at the 50-position of the HT dimer and the low probability of the HH coupling due to the steric hindrance between thiophene ring and phenyl group. Formation of Regioregular Head-to-Tail Poly[3-(4-butylphenyl)thiophene] by an Oxidative Coupling Polymerization with Vanadium Acetylacetonate ABSTRACT: The mechanism for the formation of head-to-tail (H–T) poly[3-(4-butylphenyl)thiophene] by oxidative coupling polymerization with a catalytic amount of vanadium acetylacetonate was investigated. Polymerization was carried out in the presence of vanadium acetylacetonate, trifluoromethane sulfonic acid, and trifluoroacetic anhydride under an oxygen atmosphere in 1,2-dichloroethane at room temperature. Polymers and oligomers obtained after several polymerization times were characterized by gel permeation chromatography, IR, and NMR spectroscopies. With these findings and the reactivity of monomer and dimers based on ab initio density functional theory, the polymerization was found to proceed mainly through the formation of H–T linkages due to the high spin density at the 2-position of 3-(4-butylphenyl)thiophene and the calculated total energy of dimers. 我刚来 穷的很 只发10个BB吧 |
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