Fogarty Heather A, Imhof Roman, Michl Josef
Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215, USA.
Proc Natl Acad Sci U S A. 2004 Jul 20;101(29):10517-22. doi: 10.1073/pnas.0403209101. Epub 2004 Jul 12.
Magnetic circular dichroism (MCD) of five peralkylated tetrasilanes (1-5) conformationally constrained to angles ranging from nearly 0 degrees to 180 degrees and of the open chain tetrasilane Si(4)Me(10) (6) shows a clear conformational dependence and permits the detection of previously hidden transitions. In the tetrasilane CH(2)Si(4)Me(8) (1), with the smallest dihedral angle, comparison of MCD with absorption spectra reveals four low-energy electronic transitions. In the tetrasilanes 2-4, three distinct transitions are apparent. In tetrasilanes 5 and 6, MCD reveals the very weak transition that has been predicted to be buried under the first intense peak and to which the anomalous thermochromism of 6 and other short-chain oligosilanes has been attributed.
五种构象受限的全烷基化四硅烷（1 - 5），其构象角度范围从近0度到180度，以及开链四硅烷Si(4)Me(10)（6）的磁圆二色性（MCD）显示出明显的构象依赖性，并能够检测到之前隐藏的跃迁。在二面角最小的四硅烷CH(2)Si(4)Me(8)（1）中，将MCD与吸收光谱进行比较，揭示了四个低能量电子跃迁。在四硅烷2 - 4中，有三个明显不同的跃迁。在四硅烷5和6中，MCD揭示了一个非常弱的跃迁，该跃迁预计被埋在第一个强峰之下，并且6和其他短链低聚硅烷的异常热致变色现象归因于此。
