PI-ELECTRON ABSORPTION AND CIRCULAR DICHROISM SPECTRA OF [6]-HELICENE AND [7]-HELICENE
PI-ELECTRON ABSORPTION AND CIRCULAR DICHROISM SPECTRA OF [6]-HELICENE AND [7]-HELICENE
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DOI：
10.1039/j19710000756
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发表时间：
1971-01-01
期刊：
影响因子：
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通讯作者：
MASON, SF
中科院分区：
文献类型：
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作者：
BRICKELL, WS;BROWN, A;MASON, SF
吸收和C.D.报道了[7]-螺烯的光谱，并对[6]-螺烯的电子光谱进行了重新检验。在π-SCF近似下计算了[6]-和[7]-螺烯的跃迁能、偶极强度和转动强度，并计算了理论吸收和C.D.光谱是在假设吸收带具有高斯形式的基础上得到的。发现在[5]-，[6]-和[7]-螺烯系列中，实验光谱和理论光谱之间的符合程度随着分子尺寸的增加而下降，并讨论了较高螺烯末端环上最近邻的非键碳原子之间的σ-π相互作用和π电子交换的意义。结果表明，[4]-、[5]-、[6]-和[7]-螺烯的(+)-异构体均为右旋螺旋构型。
The absorption and c.d. spectra of [7]-helicene are reported, together with a re-examination of the electronic spectrum of [6]-helicene. The transition energies and dipole and rotational strengths of [6]- and [7]-helicene have been evaluated in the π–SCF approximation, and theoretical absorption and c.d. spectra are derived on the assumption that the absorption bands have Gaussian forms. It is found that the degree of correspondence between the experimental and theoretical spectra declines with increasing molecular size over the series [5]-, [6]-, and [7]-helicene, and the significance of σ–π interaction and of π-electron exchange between the nearest-neighbour non-bonded carbon atoms in the terminal rings of the higher helicenes are discussed. It is concluded that the (+)-isomers of [4]-, [5]-, [6]-, and [7]-helicene have a right-handed helical configuration.