High Precision Electronic Spectroscopy of Ligand-Protected Gold Nanoclusters: Effects of Composition, Environment, and Ligand Chemistry.,The Journal of Physical Chemistry A

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High Precision Electronic Spectroscopy of Ligand-Protected Gold Nanoclusters: Effects of Composition, Environment, and Ligand Chemistry.
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2020-01-22 , DOI: 10.1021/acs.jpca.9b09164
Anthony Cirri ₁ , Hanna Morales Hernández ₁ , Christopher J Johnson ₁

Affiliation

Atomically precise gold nanoclusters (AuNCs) are a class of nanomaterials valued for their electronic properties and diverse structural features. While the advent of X-ray crystallography of AuNCs has revealed their geometric structures with high precision, detailed electronic structure analysis is challenged by environmental, compositional, and thermal averaging effects present in electronic spectra of typical samples. To circumvent these challenges, we have adapted mass spectrometer-based electronic absorption spectroscopy techniques to acquire high-resolution electronic spectra of atomically precisely defined nanoclusters separated from a synthetic mixture. Here we discuss recent results using this approach to link the surface chemistry of triphenylphosphine-protected AuNCs to their electronic structure and expand on key elements of the experiment and the link between these gas-phase measurements and solution-phase behavior of AuNCs. Chemically derivatized Au8(P(p-X-Ph)3)72+ and Au9(P(p-X-Ph)3)83+ clusters, where X = -H, -CH3, or -OCH3, are used to derive systematic trends in the response of the electronic spectrum to the electron-donating character of the ligand shell. We find a linear relationship between the substituent Hammett parameter σp and the transition energy between both sets of clusters' highest occupied and lowest unoccupied molecular orbitals, a transition that is localized in the metal core within the limits of the superatomic model. The similarity of the mass-selective and solution-phase UV/vis spectra of Au9(PPh3)83+ indicates that the interpretation of these experiments is transferable to the condensed phase. He and N2 environments are introduced to a series of isovalent clusters as a subtle probe of discrete environmental effects over electronic structure. Strikingly, select bands in the UV/vis spectrum respond strongly to the identity of the environment, which we interpret as a state-selective indicator of interfacially relevant electronic transitions. Physically predictable trends such as these will aid in building molecular design principles necessary for the development of novel materials based on nanoclusters.

中文翻译：

配体保护金纳米团簇的高精度电子光谱：组成，环境和配体化学的影响。

原子精确的金纳米团簇（AuNCs）是一类纳米材料，因其电子性能和多样的结构特征而受到重视。尽管AuNCs的X射线晶体学技术的出现揭示了其高精度的几何结构，但详细的电子结构分析仍受到典型样品电子光谱中存在的环境，成分和热平均效应的挑战。为了克服这些挑战，我们采用了基于质谱仪的电子吸收光谱技术，以获取从合成混合物中分离出的原子精确定义的纳米团簇的高分辨率电子光谱。在这里，我们讨论使用该方法将三苯基膦保护的AuNCs的表面化学与其电子结构联系起来的最新结果，并扩展实验的关键要素以及这些气相测量值与AuNCs的溶液相行为之间的联系。化学衍生化的Au8（P（pX-Ph）3）72+和Au9（P（pX-Ph）3）83+簇，其中X = -H，-CH3或-OCH3，用于推导该体系中的系统趋势。电子光谱对配体壳给电子特征的响应我们发现取代基的Hammett参数σp与两组簇的最高占据和最低未占据分子轨道之间的跃迁能量之间存在线性关系，该跃迁位于超原子模型范围内的金属核中。Au9（PPh3）83+的质量选择和溶液相UV / vis光谱的相似性表明，这些实验的解释可转换为缩合相。He和N2环境被引入到一系列等价簇中，作为电子结构上离散环境效应的微妙探测。令人惊讶的是，UV / vis光谱中的特定波段对环境的身份有强烈的反应，我们将其解释为界面相关电子跃迁的状态选择指标。诸如此类的可物理预测的趋势将有助于建立基于纳米团簇的新型材料开发所必需的分子设计原理。He和N2环境被引入到一系列等价簇中，作为电子结构上离散环境效应的微妙探查。令人惊讶的是，UV / vis光谱中的特定波段对环境的身份有强烈的反应，我们将其解释为界面相关电子跃迁的状态选择指标。诸如此类的可物理预测的趋势将有助于建立基于纳米团簇的新型材料开发所必需的分子设计原理。He和N2环境被引入到一系列等价簇中，作为电子结构上离散环境效应的微妙探查。令人惊讶的是，UV / vis光谱中的特定波段对环境的身份有强烈的反应，我们将其解释为界面相关电子跃迁的状态选择指标。诸如此类的可物理预测的趋势将有助于建立基于纳米团簇的新型材料开发所必需的分子设计原理。

更新日期：2020-01-23

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