Circular dichroism of helicenes investigated by time-dependent density functional theory
Circular dichroism of helicenes investigated by time-dependent density functional theory
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DOI：
10.1021/ja991960s
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发表时间：
2000-03-01
影响因子：
15
通讯作者：
Grimme, S
中科院分区：
文献类型：
--
作者：
Furche, F;Ahlrichs, R;Grimme, S
结果表明，用绝热含时密度泛函理论(TDDFT)可以系统地研究分子电子圆二色(CD)。我们简要地总结了这一理论，并概述了它在计算转动强度方面的扩展。在TURBOMOLE程序包中实现了一种新的、高效的算法，使大规模应用成为可能。对螺烯类化合物圆二色性的研究对于理解分子的旋光性起着至关重要的作用。我们首次用从头算方法模拟了[n]螺烯(n=4-7，12)的电子CD谱，考虑了取代基的影响，新记录了这些化合物的实验CD谱。计算正确地再现了最重要的光谱特征，并极大地方便了解释。我们建议根据单个激发态对低能带进行指认。计算了观察到的光谱随环的数目和取代方式的变化，并对其进行了合理化。讨论了TDDFT在化工应用中的优点和局限性。
It is shown that molecular electronic circular dichroism (CD) can systematically be investigated by means of adiabatic time-dependent density functional theory (TDDFT). We briefly summarize the theory and outline its extension for the calculation of rotatory strengths. A new, efficient algorithm has been implemented in the TURBOMOLE program package for the present work, making large-scale applications feasible. The study of circular dichroism in helicenes has played a crucial role in the understanding of molecular optical activity. We present the first ab initio simulation of electronic CD spectra of [n]helicenes, n = 4-7, 12. Substituent effects are considered for the 2,15-dicyano and 2,15-dimethoxy derivates of hexahelicene; experimental CD spectra of these compounds were newly recorded for the present work. The calculations correctly reproduce the most important spectral features and greatly facilitate interpretation. We propose assignments of the low-energy bands in terms of individual excited states. Changes in the observed spectra depending on the number of rings and substitution patterns are worked out and rationalized. Merits and limitations of TDDFT in chemical applications are discussed.