Atomically precise metal nanoclusters, stabilized and functionalized by organic ligands, are emerging nanomaterials with potential applications in plasmonics, nano-electronics, bio-imaging, nanocatalysis, and as therapeutic agents or drug carriers in nanomedicine. The ligand layer has an important role in modifying the physico-chemical properties of the clusters and in defining the interactions between the clusters and the environment. While this role is well recognized from a great deal of experimental studies, there is very little theoretical information on dynamical processes within the layer itself. Here, we have performed extensive molecular dynamics simulations, with forces calculated from the density functional theory, to investigate thermal stability and dynamics of the ligand layer of the meta-mercaptobenzoic acid (m-MBA) protected Au₆₈ and Au₁₄₄ nanoclusters, which are the first two gold nanoclusters structurally solved to atomic precision by electron microscopy [Azubel et al., Science, 2014, 345, 909 and ACS Nano, 2017, 11, 11866]. We visualize and analyze dynamics of three distinct non-covalent interactions, viz., ligand–ligand hydrogen bonding, metal–ligand OC–OH⋯Au interaction, and metal–ligand Ph(π)⋯Au interaction. We discuss their relevance for defining, at the same time, the dynamic stability and reactivity of the cluster. These interactions promote the possibility of ligand addition reactions for bio-functionalization or allow the protected cluster to act as a catalyst where active sites are dynamically accessible inside the ligand layer.

中文翻译：

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巯基苯甲酸保护的金纳米团簇Au68（m-MBA）32和Au144（m-MBA）40的配体层中弱相互作用的动力学

通过有机配体稳定和功能化的原子精确的金属纳米簇是新兴的纳米材料，在等离子体，纳米电子学，生物成像，纳米催化中具有潜在应用，并在纳米医学中用作治疗剂或药物载体。配体层在改变团簇的物理化学性质以及定义团簇与环境之间的相互作用方面具有重要作用。尽管从大量的实验研究中可以很好地认识到这一作用，但是在层本身内部的动力学过程方面却很少有理论信息。在这里，我们已经进行了广泛的分子动力学模拟，并利用密度泛函理论计算了力，以研究热稳定性和间位配体层的动力学。-巯基苯甲酸（m -MBA）保护金₆₈和金₁₄₄纳米簇，这是通过电子显微镜在结构上已解决原子精度的两个金纳米簇[Azubel等。，科学，2014，345，909和ACS纳米，2017年，11，11866]。我们可视化并分析了三种不同的非共价相互作用的动力学，即配体-配体氢键，金属-配体OC-OH⋯Au相互作用和金属-配体Ph（π）⋯Au相互作用。我们讨论了它们在定义簇的动态稳定性和反应性的同时的相关性。这些相互作用促进了配体加成反应用于生物功能化的可能性，或使受保护的簇充当催化剂，其中活性位点可在配体层内部动态访问。