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用硼环Bn平面配位金属中心M,两者必须在几何和电子结构上良好匹配.对Al和Ga而言,B8环半径略小,完全平面的D8hAl@B8-(1)和D8hGa@B8-(3)均为具有一个虚频的过渡态;金属中心沿体系八重轴轻微向上移动(0.3~0.5)所形成的C8vAl@B8-(2)和C8vGa@B8-(4)才是体系的稳定几何构型.轻微畸变的C8v阴离子具有准平面结构,与D8h平面结构在能量上非常接近.广泛的结构搜索表明,B9环与Al和Ga中心良好匹配,D9hAl@B9(5)与D9hGa@B9(6)均为直径约4.45的完美轮状中性分子,它们在得到的所有异构体中能量最低.在D9h5和6中,Al和Ga平面九配位中心携带的净原子电荷分别为+1.3|e|和+1.5|e|,其Wiberg总键级为2.5和2.8;而周边相邻B-B原子间的WBIB-B键级接近1.5,具有明显的双键特征.D9hAl@B9中中心原子的电子组态(Al3s0.423px0.343py0.343pz0.34)表明,Al在配合物中主要失去3s2价电子,其sp2杂化轨道和3pz原子轨道部分参与了体系的离域σ键和离域π键.结果表明,D9hAl@B9有三个离域的π轨道(简并的HOMO和HOMO-2)和三个离域的σ轨道(简并的HOMO-1和HOMO-4),分别符合4n+2休克尔芳香性规则,因而具有σ+π双重芳香性.M@B8-和M@B9(M=Al,Ga)体系的核独立化学位移(NICS(1))均为较大的负值(介于-17~-26ppm),进一步确定了体系的芳香性本质.C8vAl@B8-和C8vGa@B8-阴离子的计算单电子剥离能分别为ADE=3.41,3.23eV和VDE=3.52,3.32eV,而D9hAl@B9和D9hGa@B9中性分子的计算第一电离势分别为IP=8.51,8.34eV.这些结果为在光电子能谱实验中表征这些分子提供了依据.
B-plane Bn planar coordination metal center M, both must have a good geometric and electronic structural fit For Al and Ga, B8 ring slightly smaller radius, fully planar D8hAl @ B8- (1) and D8hGa @ B8 - (3) are both transition states with an imaginary frequency; the C8vAl @ B8- (2) and C8vGa @ B8- (4) formed by the metal center moving slightly upwards from the octapetrum of the system (0.3-0.5) Stable geometry The slightly distorted C8v anions have a quasi-planar structure that is energetically very close to the D8h plane structure.The extensive structural search shows that the B9 ring is well matched to the Al and Ga centers and the D9hAl @ B9 (5) and D9hGa @ B9 (6) are the perfect round neutral molecules with a diameter of about 4.45, which have the lowest energies in all the isomers obtained.In D9h5 and 6, the net atomic charges carried by the nine coordination centers of Al and Ga plane are +1.3 | e | and +1.5 | e |, and the Wiberg total bond order is 2.5 and 2.8, while the WBIB-B bond level between neighboring neighboring BB atoms is close to 1.5 and has obvious double bond characteristics. Atomic electronic configuration (Al3s0.423px0.343py0.343pz0.34) shows that Al mainly lost 3s2 valence electrons in the complex, and its sp2 hybrid orbitals and 3pz atomic orbitals partially participate in the delocalization of the system (Delocalized HOMO and HOMO-2) and three delocalized σ orbitals (degenerate HOMO-1 and HOMO-4) Respectively meet the 4n + 2 Shucker aromaticity rule and thus have a double aromaticity of σ + π. The nucleus independent chemical shifts (NICS (1)) of the M @ B8- and M @ B9 (M = Al, Ga) Large negative values (-17 ~ -26ppm), further confirmed the aromatic nature of the system.C8vAl @ B8- and C8vGa @ B8- anions calculated single-electron peel ADE = 3.41,3.23eV and VDE = 3.52 and 3.32eV, respectively, while the calculated first ionization potentials of D9hAl @ B9 and D9hGa @ B9 neutrals were IP = 8.51 and 8.34eV, respectively. These results provide the basis for the characterization of these molecules in photoelectron spectroscopy experiments.