This study employs density functional theory(DFT)calculations to systematically investigate the B‒H bond dissociation enthalpies(BDEs)of Lewis base‒borane complexes.A rigorous benchmark analysis identified theωB97XD/...This study employs density functional theory(DFT)calculations to systematically investigate the B‒H bond dissociation enthalpies(BDEs)of Lewis base‒borane complexes.A rigorous benchmark analysis identified theωB97XD/cc-pVTZ method as a reliable method for accurate prediction of B–H BDEs.An examination of more than 200 structurally diverse complexes across five major classes revealed that the type of Lewis base significantly influences the BDEs,with the order of amine–borane>phosphine–borane>N-heterocyclic carbene–borane>pyridine–borane.Solventstabilized boranes exhibit the broadest range of BDE values due to the diverse coordination modes of solvent molecules with borane.Further analysis revealed that the BDE values are synergistically affected by skeletal and substituent effects.Notably,a strong linear correlation(R^(2) up to 0.97)between the spin density of boryl radicals and BDEs,except for amine–boranes,provides a robust predictive model.This research enhances the fundamental understanding of B‒H bond dissociation properties in Lewis base–boranes and provides valuable insights for the development of new boron-based methodologies in organic synthesis.展开更多
应用正、反相硅胶和葡聚糖凝胶柱色谱等技术对藜(Chenopodium album L.)的黄酮类化学成分进行了分离和纯化.从藜中分离得到2种黄酮类化合物,分别为异鼠李素3-O-芸香糖苷(1)、槲皮素3-O-β-D-呋喃芹糖(1→2)-O-[α-L-鼠李糖(1→6)]-β-D...应用正、反相硅胶和葡聚糖凝胶柱色谱等技术对藜(Chenopodium album L.)的黄酮类化学成分进行了分离和纯化.从藜中分离得到2种黄酮类化合物,分别为异鼠李素3-O-芸香糖苷(1)、槲皮素3-O-β-D-呋喃芹糖(1→2)-O-[α-L-鼠李糖(1→6)]-β-D-葡萄糖苷(2).采用纸片扩散法进行了抑菌试验.结果表明,黎的95%(体积分数)乙醇提取液对大肠埃希菌有明显的抑菌效果,最低抑菌浓度(MIC)为32mg/L.展开更多
On the basis of density functional theory and electronegativity equalization princi-ple, a new scheme has been developed for determination of atomic charges and bond charges in large molecules. In the new scheme, the ...On the basis of density functional theory and electronegativity equalization princi-ple, a new scheme has been developed for determination of atomic charges and bond charges in large molecules. In the new scheme, the molecular electron density ρmol(r) is partitioned as where ρα(r) and ρα-β(r) are the electron densities located on the atom α and bond α-β, respectively. The parameters A, B, C and D are the valence-state electronegativity and valence-state hardness. They are obtained by calibrating through model molecule calculations and are transferable and consistently usable for calculating the charge distributions in large molecules. The new scheme is tested through determination of atomic charges and bond charges in several large molecules. It has been shown that the re-sults of atomic charges and bond charges obtained by the new scheme dovetail those obtained by ab initio method very well. In addition, the new scheme presented here has the advantage of simplicity, rapidness and easy perform as well, so that it provides an efficient and practi-cal method for calculation of the charge distribution for a macromolecular system.展开更多
基金supported by the USTC Research Funds of the Double First-Class Initiative(YD2060006004,YD2060002027)the National Natural Science Foundation of China(22325107,22171253,22293011).
文摘This study employs density functional theory(DFT)calculations to systematically investigate the B‒H bond dissociation enthalpies(BDEs)of Lewis base‒borane complexes.A rigorous benchmark analysis identified theωB97XD/cc-pVTZ method as a reliable method for accurate prediction of B–H BDEs.An examination of more than 200 structurally diverse complexes across five major classes revealed that the type of Lewis base significantly influences the BDEs,with the order of amine–borane>phosphine–borane>N-heterocyclic carbene–borane>pyridine–borane.Solventstabilized boranes exhibit the broadest range of BDE values due to the diverse coordination modes of solvent molecules with borane.Further analysis revealed that the BDE values are synergistically affected by skeletal and substituent effects.Notably,a strong linear correlation(R^(2) up to 0.97)between the spin density of boryl radicals and BDEs,except for amine–boranes,provides a robust predictive model.This research enhances the fundamental understanding of B‒H bond dissociation properties in Lewis base–boranes and provides valuable insights for the development of new boron-based methodologies in organic synthesis.
文摘应用正、反相硅胶和葡聚糖凝胶柱色谱等技术对藜(Chenopodium album L.)的黄酮类化学成分进行了分离和纯化.从藜中分离得到2种黄酮类化合物,分别为异鼠李素3-O-芸香糖苷(1)、槲皮素3-O-β-D-呋喃芹糖(1→2)-O-[α-L-鼠李糖(1→6)]-β-D-葡萄糖苷(2).采用纸片扩散法进行了抑菌试验.结果表明,黎的95%(体积分数)乙醇提取液对大肠埃希菌有明显的抑菌效果,最低抑菌浓度(MIC)为32mg/L.
文摘On the basis of density functional theory and electronegativity equalization princi-ple, a new scheme has been developed for determination of atomic charges and bond charges in large molecules. In the new scheme, the molecular electron density ρmol(r) is partitioned as where ρα(r) and ρα-β(r) are the electron densities located on the atom α and bond α-β, respectively. The parameters A, B, C and D are the valence-state electronegativity and valence-state hardness. They are obtained by calibrating through model molecule calculations and are transferable and consistently usable for calculating the charge distributions in large molecules. The new scheme is tested through determination of atomic charges and bond charges in several large molecules. It has been shown that the re-sults of atomic charges and bond charges obtained by the new scheme dovetail those obtained by ab initio method very well. In addition, the new scheme presented here has the advantage of simplicity, rapidness and easy perform as well, so that it provides an efficient and practi-cal method for calculation of the charge distribution for a macromolecular system.
