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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >UV, MCD, and LD Spectra of a Conformationally Constrained ortho-tetrasilane: Support for the Avoided Crossing Model of Conformational Effects of Excited States
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UV, MCD, and LD Spectra of a Conformationally Constrained ortho-tetrasilane: Support for the Avoided Crossing Model of Conformational Effects of Excited States

机译：构象受限的邻四硅烷的UV，MCD和LD光谱：支持激发态构象效应避免交叉模型

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摘要

UV absorption, magnetic circular (MCD), and linear (LD) dichroism of an n-tetrasilane configurationally constrained to the ortho conformation (calculated SiSiSiSi dihedral angle #omega# approx= 95 deg) are reported, and the results are compared with the theoretical expectation of four low-energy transitions. Two strong UV absorption maxima with similar intensity and positive MCD B terms are assigned to states of B symmetry. A third calculated transition to an 2~1A state was clearly detected in the LD spectrum, but a calculated weak transition to a 3~1A state at a higher energy was not observed. The results support a previous rationalization of the conformational properties of the n-tetrasilane chromophore, according to which one of two low-energy transitions into B-symmetry states is of #sigma##sigma# and the other of #sigma##pi# type in the planar cis and anti limits, and they undergo a strongly avoided crossing as #omega# changes from 0 deg C to 180 deg C, keeping their energies nearly constant but interchanging their oscillator strengths.
机译：报告了配置为邻位构象的正四硅烷的紫外吸收，磁圆（MCD）和线性（LD）二色性（计算得出的SiSiSiSi二面角＃omega＃大约= 95度），并将结果与​​理论值进行了比较对四个低能转换的期望。将具有相似强度和正MCD B项的两个强UV吸收最大值分配给B对称状态。在LD光谱中清楚地检测到第三个计算到2〜1A状态的跃迁，但是没有观察到在较高能量下计算到3〜1A状态的弱跃迁。结果支持先前对正四硅烷发色团构象性质的合理化，据此，两个低能转变为B对称态的一个是＃sigma ## sigma＃，另一个是＃sigma ## pi＃在＃omega＃从0摄氏度变化到180摄氏度时，强烈避免了交叉，因为它们的能量几乎保持恒定，但交换了振荡器的强度。

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