Interaction of clusters with chiral surfaces

簇与手性表面的相互作用

• 批准号: 262670452
• 负责人: Professor Dr. Ulrich Heiz
• 金额: --
• 依托单位: Department of Chemistry
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/262670452?language=en
• 关键词: Interaction; clusters; chiral; surfaces

In the present research proposal, we aim to induce chirality in catalytically active, size-selected metal clusters through interaction with chiral surfaces and focus on the detection and the fundamental understanding of the origin of this asymmetrization. While the induced cluster chirality may promote enantioselectivity, these systems may also reveal high activity, since the catalyst will be fully accessible for reactant molecules from the gas phase. This approach for designing asymmetric catalyst is fundamentally different from the various attempts, taken in the past to heterogenize efficient, asymmetric homogeneous catalysts by immobilization on a variety of support materials. In detail, the objective of this research proposal is to prepare and characterize a variety of chiral surfaces ranging from chiral molecular monolayers to chiral oxides and to detect possible chirality transfer to metal clusters upon deposition in a size range from a couple of atoms up to about 100 atoms. We will particularly focus on metal clusters and clusters sizes with high reactivity and well positioned optical transitions, i.e. with optical transitions within the spectral range available to us and not interfering with the ones of the chiral support. Up to date, there are no reports on the successful detection of chirality transfer into supported metal clusters. To this end we have overcome the main challenge, i.e. the incapability to detect small chiroptical features by developing a new highly sensitive spectroscope based on nonlinear methods. Although second harmonic generation circular dichroism (SHG-CD) allows for detecting small optical activities, it is limited, according to the corresponding selection rules, to optical transitions with a transition dipole moment non-parallel to the surface. Accordingly, another challenge will not only be to discover combinations of size-selected metal clusters and chiral surfaces with an efficient chirality transfer but also to find a system where the optical response of the catalyst is not destructively influenced by the underlying chiral surface. In this respect chiral oxide surfaces may be particularly promising. Once the chirality transfer has been successfully identified, we will also study the thermal stability and the accessibility of reaction sites.

在本研究建议中，我们旨在通过与手性表面相互作用来诱导催化活性，大小选择的金属簇的手性，并专注于检测和对这种不对称起源的基本理解。虽然诱导的簇手性可以促进对映选择性，但这些系统也可能揭示高活性，因为从气相的反应物分子可以完全访问催化剂。这种设计不对称催化剂的方法与过去的各种尝试从​​根本上有所不同，这些尝试是通过固定在各种支持材料上，以使有效的，不对称的均质催化剂化。详细介绍，这项研究建议的目的是准备和表征各种手性表面，从手性分子单层到手性氧化物，并检测到在沉积中的手性转移到金属簇中的可能性范围从几个原子到大约100个原子。我们将特别关注具有高反应性和良好位置的光学跃迁的金属簇和簇大小，即在我们可用的光谱范围内进行光学跃迁，并且不会干扰手性支撑的光谱。最新的是，没有关于成功发现手性转移到支持的金属簇的报告。为此，我们克服了主要的挑战，即通过开发基于非线性方法的新的高度敏感光谱仪来检测小小的手势特征的能力。尽管第二次谐波产生圆二色性（SHG-CD）允许检测小型光学活动，但根据相应的选择规则，它被限制为具有与表面不平衡的过渡偶极矩的光学跃迁。因此，另一个挑战将不仅是发现具有有效的手性转移的尺寸选择的金属簇和手性表面的组合，而且要找到一个系统，即催化剂的光学响应不会受到潜在手性表面的破坏性影响。在这方面，手性氧化物表面可能特别有前途。一旦成功鉴定出手性转移，我们还将研究反应部位的热稳定性和可访问性。