Abstract

We report on time-dependent density functional theory calculations to study the chiroptical properties of small \(\hbox {Nb}_{{9}}\) clusters and their corresponding van der Waals \(\hbox {Nb}_{{9}}\hbox {Ar}_{n}\) complexes. The three most stable 9-atom structures considered in the literature are analyzed, and we obtain their lowest-energy atomic configurations, UV–Vis response, and for the first time, the electronic circular dichroism (ECD) spectra of the systems. Excitation energies, as well as oscillator and rotational strengths are calculated using the M06 exchange-correlation functional together with a mixed basis approach where all electron DGDZVP and Def2SV basis are employed for Nb and Ar atoms, respectively. In all cases, the UV–Vis spectra look very similar and are characterized by the formation of a main absorption maxima located at \(\sim 240\hbox { nm}\); however, the distribution of simulated ECD signals strongly depends on the geometrical structure of the clusters. Our calculated ECD bands show precise features that cover the experimentally accessible 200–300 nm range and extend near the visible part of the spectra, a fact that allows us to distinguish between different niobium cluster geometries. However, weighted averages of calculated ECD spectra for different \(\hbox {Nb}_{{9}}\) clusters reveal that isomerization effects might lead to a notable increase/reduction in the intensity of CD lines since the simulated bands could add or cancel each other.

Graphic abstract

中文翻译：

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小铌团簇的手性

摘要

我们报告了与时间有关的密度泛函理论计算，以研究小型\（\ hbox {Nb} _ {{9}} \）团簇及其相应的范德华\（\ hbox {Nb} _ {{9 }} \ hbox {Ar} _ {n} \）复合体。分析了文献中考虑的三个最稳定的9原子结构，我们获得了它们的最低能量原子构型，UV-Vis响应以及系统的首次电子圆二色性（ECD）光谱。使用M06交换相关函数以及混合基础方法（其中所有电子DGDZVP和Def2SV基础分别用于Nb和Ar原子）来计算激发能以及振荡器和旋转强度。在所有情况下，UV-Vis光谱看起来都很相似，其特征是位于\（\ sim 240 \ hbox {nm} \）处的主吸收最大值形成; 但是，模拟的ECD信号的分布在很大程度上取决于群集的几何结构。我们计算出的ECD波段显示出精确的特征，涵盖了实验上可访问的200-300 nm范围，并延伸到光谱的可见部分附近，这一事实使我们能够区分不同的铌簇几何形状。但是，不同\（\ hbox {Nb} _ {{9}} \）簇的计算出的ECD光谱的加权平均值表明，异构化效应可能导致CD谱线强度的显着增加/减少，因为模拟谱带可能会增加或互相取消。

图形摘要