Ligand Regiochemistry on Gold Nanoclusters

在化学系大分子、超分子和纳米化学项目（MSN）的支持下，科罗拉多州立大学的Christopher Ackerson教授正在将化学合成和先进的化学分析工具相结合，研究不同类型的分子如何竞争金原子簇表面的键合位点。 这些表面可以是低对称性的，这意味着存在许多不同类型的键合位点。不同类型的分子偏好不同类型的键合位点。 有些分子会同时结合到两个位点上。 为了确定哪些分子更喜欢哪些结合位点，Ackerson教授和他的学生制作了定义明确的金簇，例如Au 25，它有18个分子结合位点。 他们将Au 25与其他分子混合，并使用先进的成像方法来观察分子结合的位置。 从长远来看，他们希望写出描述分子与金属簇结合的规则。 他们的发现可能会导致制造目前无法合成的大分子的方法。 这些分子可以用于催化，作为显微镜的标记，以及作为药物。 该奖项支持一个研讨会，汇集了来自不同的化学亚专业的合成专家，以及培训多样化的未来科学劳动力。Ackerson教授旨在改变目前对金属纳米颗粒表面配体区域化学控制的理解。检查的具体系统是，硫醇盐，乙炔化物，和类似的配体上幻数金簇。这些簇具有低对称性（例如，符合C2，i和类似的点群），这意味着存在许多独特的配体结合位点。总体目标是了解单齿配体的区域化学，这样的金纳米团簇，并确定结构上如何双齿硫醇配体绑定到幻数金簇。 所讨论的问题包括：（1）什么反应机制访问网站的长期寿命？ (2)具有独特或苛刻R基团的硫醇盐是否基于其形状定位于特定的区域化学位点？(3)乙炔配体在环境条件下会发生缔合交换吗？(4)二齿巯基配体结合的结构本质是什么？ (5)在单齿配体继续交换的环境条件下，双齿配体是否能达到有用的寿命（几天到几周）？ (6)一个完全由双齿配体保护的幻数簇能被产生和结晶吗？这些问题是解决与方法的方法，包括MALDI-MS来确定配体交换的程度，无论是单晶X射线衍射或多维NMR光谱，以确定regiochemistry的配体交换products.This奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

With support from the Macromolecular, Supramolecular and Nanochemistry Program (MSN) in the Division of Chemistry, Professor Christopher Ackerson of Colorado State University is combining chemical synthesis and advanced chemical analysis tools to study how different types of molecules compete for bonding sites on the surfaces of clusters of gold atoms. These surfaces can be low-symmetry, meaning that many different types of bonding sites are present. Different types of molecules prefer different types of bonding sites. Some molecules will bond to two sites at the same time. To determine which molecules prefer which binding sites, Professor Ackerson and his students make well-defined gold clusters, such as Au25, which has 18 molecule binding sites. They mix Au25 with other molecules and use advanced imaging methods to see where the molecules bind. In the long term, they want to write rules that describe where molecules will bind to metal clusters. Their discoveries could lead to methods for making large molecules that cannot currently be synthesized. Those molecules could find use in catalysis, as labels in microscopy, and as medicines. The award supports a workshop that brings together synthetic experts from different sub-specialties in chemistry, as well as training the diverse future scientific workforce.Professor Ackerson aims to transform current understanding of regiochemical control of ligands on metal nanoparticle surfaces. The specific system examined is that of thiolate, acetylide, and similar ligands on magic number gold clusters. These clusters are of low symmetry (e.g., conforming to C2, i, and similar point groups), meaning that there are many symmetry-unique ligand binding sites. The overall goals are to understand the regiochemistry of monodentate ligands on such gold nanoclusters and to determine structurally how bidentate thiolate ligands bind to magic number gold clusters. Questions addressed include: (1) What reaction mechanisms access sites with long-term lifetimes? (2) Do thiolates with distinctive or demanding R-groups localize to specific regiochemical sites based on their shape? (3) Do acetylide ligands exchange associatively under ambient conditions? (4) What is the structural nature of bidentate thiol ligand binding? (5) Do bidentate ligands achieve useful lifetimes (days to weeks) in ambient conditions where monodentate ligands continue to exchange? (6) Can a magic-number cluster protected exclusively by bidentate ligands be produced and crystallized? These questions are addressed with methodological approaches including MALDI-MS to determine extent of ligand exchange, and either single crystal X-ray diffraction or multidimensional NMR spectroscopy to determine regiochemistry of ligand-exchange products.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.