Alexandrova Anastassia N, Boldyrev Alexander I, Zhai Hua-Jin, Wang Lai-Sheng
Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322-0300, USA.
J Chem Phys. 2005 Feb 1;122(5):54313. doi: 10.1063/1.1839575.
A metal-boron mixed cluster LiB(6) (-) was produced and characterized by photoelectron spectroscopy and ab initio calculations. A number of electronic transitions were observed and used to compare with theoretical calculations. An extensive search for the global minimum of LiB(6) (-) was carried out via an ab initio genetic algorithm technique. The pyramidal C(2v) ((1)A(1)) molecule was found to be the most stable at all levels of theory. The nearest low-lying isomer was found to be a triplet C(2) ((3)B) structure, 9.2 kcal/mol higher in energy. Comparison of calculated detachment transitions from LiB(6) (-) and the experimental photoelectron spectra confirmed the C(2v) pyramidal global minimum structure. Natural population calculation revealed that LiB(6) (-) is a charge-transfer complex, Li(+)B(6) (2-), in which Li(+) and B(6) (2-) interact in a primarily ionic manner. Analyses of the molecular orbitals and chemical bonding of B(6) (2-) showed that the planar cluster is twofold (pi- and sigma-) antiaromatic, which can be viewed as the fusion of two aromatic B(3) (-) units.
通过光电子能谱和从头算计算制备并表征了一种金属硼混合簇LiB₆⁻。观察到许多电子跃迁，并用于与理论计算进行比较。通过从头算遗传算法技术对LiB₆⁻的全局最小值进行了广泛搜索。发现金字塔形C₂ᵥ（¹A₁）分子在所有理论水平上都是最稳定的。发现最近的低能异构体是三重态C₂（³B）结构，能量高9.2千卡/摩尔。对LiB₆⁻计算的离解跃迁与实验光电子能谱的比较证实了C₂ᵥ金字塔形全局最小结构。自然布居计算表明LiB₆⁻是一种电荷转移络合物Li⁺B₆²⁻，其中Li⁺和B₆²⁻主要以离子方式相互作用。对B₆²⁻的分子轨道和化学键的分析表明，平面簇是双重（π和σ）反芳香性的，可视为两个芳香性B₃⁻单元的融合。
