关键词: 苯基二硅烷, 硅硅键, 紫外吸收, σ-π共轭, 电荷转移

The interaction of silicon-silicon-bonds and phenyl-systems in phenyldisilanes and the resulted characteristic UV absorptions have been one of the fundamental issues of organosilicon chemistry. However, the interaction between two phenyl groups and the central silicon-silicon bond in 1,2-diphenyltetramethyldisilanes and its correlation with the characteristic UV absorptions remain uncompletely solved. In this paper, a series of unsymmetric substituted 1,2-diphenyltetramethyldisilanes, namely C₆H₅SiMe₂SiMe₂C₆H₄-p-COMe (3), p-MeOC₆H₄SiMe₂SiMe₂C₆H₄-p-COMe (4), C₆H₅SiMe₂SiMe₂C₆H₄-p-NMe₂ (5) and p-MeOC₆H₄SiMe₂SiMe₂C₆H₄-p-NMe₂ (6), have been synthesized and characterized by ¹H NMR, ¹³C NMR, IR and elemental analyses, and their UV absorption properties were studied. It is found that each of the compounds exhibits two characteristic absorption bands at the long wavelength region of the UV spectra, which corresponds to the absorptions produced when individual substituted phenyl groups are linked to silicon-silicon bonds. No obvious bathochromic shifts due to interaction between two substituted phenyl groups through the silicon-silicon bond have been observed. This indicates that the traditional explanation of characteristic UV absorptions of phenyldisilanes in terms of conjugation between silicon-silicon bonds and phenyl groups should be re-examined.

Key words: phenyldisilanes, silicon-silicon bonds, UV absorption, σ-&pi, conjugation, charge transfer