[2]Staffane Rod as a Molecular Rack for Unraveling Conformer Properties: Proposed Singlet Excitation Localization Isomerism in anti,anti,anti-Hexasilanes
[2]Staffane Rod as a Molecular Rack for Unraveling Conformer Properties: Proposed Singlet Excitation Localization Isomerism in anti,anti,anti-Hexasilanes
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[2]Staffane Rod 作为解开构象异构体性质的分子架：提出的抗、抗、抗六硅烷中的单线态激发局域化异构现象
DOI：
10.1021/ja971059h
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发表时间：
1997
影响因子：
15
通讯作者：
J. Michl
中科院分区：
文献类型：
--
作者：
S. Mazières;M. Raymond;G. Raabe;A. Prodi;J. Michl
由于饱和AnX 2n + 2链的构象数多且难以分离，因此对溶液中单个构象的测量是罕见的。链构象可能会影响其电子结构，因为σ键离域对周围价6相互作用敏感3 -5，例如在聚硅烷中。7我们比较了全甲基化六硅烷（1）与自由链构象混合物Si 6-Me 14（2）的温度依赖性几何物理学，全甲基化六硅烷（1）通过在透明[2] staffane“Tinkertoy”8棒9，10上挤压而被限制为全反式。由Cl（SiMe 2）6Cl 13和[2] staffane-3，3′-二硫醇10（方案1，环化产率24%）获得的架状六硅烷111（图1），12具有未应变的完全拉伸的硅链[从Si（1）到Si（6）为9.79 π]。Si-Si键长（2.345-2.355 Ω）、SiSiSi价（110.8-113.9）和SiSiSiSi二面角（162.5，178.0，177.4）符合全反式的预期。5 MM 214计算仅产生了1的这种低能构象，但产生了2的许多构象。
Because of the large number and difficult separation of conformers of saturated AnX2n+ 2 chains longer than n) 4, 1, 2 measurements on an individual conformer in solution are rare. Chain conformation may affect its electronic structure, as σ bond delocalization is sensitive3-5 to perivalent6 interactions, eg, in polysilanes. 7 We compare the temperature-dependent photophysics of a permethylated hexasilane (1) constrained to the all-anti form by racking on a transparent [2] staffane “Tinkertoy” 8 rod9, 10 with that of the free chain conformer mixture, Si6-Me14 (2). Both show dual fluorescence, assigned to excited state bond-stretch isomerism.The racked hexasilane 111 (Figure 1), 12 obtained from Cl (SiMe2) 6Cl13 and [2] staffane-3, 3′-dithiol10 (Scheme 1, cyclization yield 24%), has an unstrained fully stretched silicon chain [9.79 Å from Si (1) to Si (6)]. The Si-Si bond lengths (2.345-2.355 Å), SiSiSi valence (110.8-113.9), and SiSiSiSi dihedral angles (162.5, 178.0, 177.4) meet expectations for the all-anti form. 5 MM214 calculations yielded only this low-energy conformation for 1 but many conformations for 2.