Ehara Masahiro, Fukawa Shuhei, Nakatsuji Hiroshi, David Donald E, Pinkhassik Evgueni Z, Levin Michael D, Apostol Marcin, Michl Josef
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Chem Asian J. 2007 Aug 3;2(8):1007-19. doi: 10.1002/asia.200600411.
He(I) photoelectron spectroscopy was used to examine the valence-shell electronic structure of three new and seven previously known bicyclo[1.1.1]pentane derivatives, 1,3-Y2-C5X6 (for X = H, Y = H, Cl, Br, I, CN; for X = F, Y = H, Br, I, CN). A larger series (X = H or F, Y = H, F, Cl, Br, I, At, CN) has been studied computationally with the SAC-CI (symmetry-adapted cluster configuration interaction) method. The outer-valence ionization spectra calculated by the SAC-CI method, including spin-orbit interaction, reproduced the experimental photoelectron spectra well, and quantitative assignments are given. When the extent of effective through-cage interaction between the bridgehead halogen lone-pair orbitals was defined in the usual way by orbital-energy splitting, it was found to be larger than that mediated by other cages such as cubane, and was further enhanced by hexafluorination. The origin of the orbital-energy splitting is analyzed in terms of cage structure, and it is pointed out that its relation to the degree of interaction between the bridgehead substituents is not as simple as is often assumed.
采用He(I)光电子能谱研究了三种新的和七种先前已知的双环[1.1.1]戊烷衍生物1,3 - Y₂ - C₅X₆（其中X = H，Y = H、Cl、Br、I、CN；X = F，Y = H、Br、I、CN）的价层电子结构。利用SAC - CI（对称适配簇组态相互作用）方法对一个更大的系列（X = H或F，Y = H、F、Cl、Br、I、At、CN）进行了计算研究。通过SAC - CI方法计算得到的包括自旋 - 轨道相互作用的外层价电离光谱很好地再现了实验光电子能谱，并给出了定量归属。当以通常的轨道能量分裂方式定义桥头卤素孤对轨道之间的有效穿笼相互作用程度时，发现其比由其他笼状结构（如立方烷）介导的相互作用程度更大，并且通过六氟化作用进一步增强。从笼状结构的角度分析了轨道能量分裂的起源，并指出其与桥头取代基之间相互作用程度的关系并不像通常所认为的那么简单。
