The importance of electronically excited states and of the electron spin on the reactivity of metal dimers and small clusters: matrix isolation experiments and quantum chemical calculations

电子激发态和电子自旋对金属二聚体和小团簇反应性的重要性：矩阵隔离实验和量子化学计算

基本信息

批准号：
260579771
负责人：
Professor Dr. Hans-Jörg Himmel
金额：
--
依托单位：
Anorganisch-Chemisches Institut
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/260579771?language=en
关键词：
importance electronically excited states electron

项目摘要

Metal and metaloxide cluster models are extremely important to develop mechanistic concepts of heterogenous catalytic reactions. The large number of eneregtically low-lying electronically excited states, that are populated already at room temperature, are responsible for the high reactivity and selectivity of cluster reactions. It allows the cluster to flexibly adjust its electronic structure so that it ideally fits to the reaction with a substrate molecule. Besides gas-phase studies, measurements with the help of the matrix-isolation technique provide significant contributions to this research theme. The matrix-isolation technique is ideally suited to study the reactivity of electronically excited states of these clusters. The low temperatures (4 - 40 K) of the matrix garantee that all clusters are first in their electronic ground state. By light irradiation they can be selectively excited. The Heidelberg matrix apparatus (self-made) is especially designed for such experiments. It allows absorption measurements (IR and vis-NIR) with high resolution in the range 10 - 25000 cm-1, as well as emission measurements (Raman and fluorescence). The clusters can be excited with a laser of narrow bandwidth.While a major part of the work during the first funding period was concerned with the characterization of clusters in their electronic ground state and in energetically low-lying excited states, the work in the second period concentrates almost exclusively on the reactivities of the clusters in dependence of their electronic state. The results from the first funding period and other results from our group provide the basis for these studies. The objects are vanadium- and vanadium oxide molecules (subproject A) and titanium- and titanium oxide molecules (subproject B). The electronic states of these molecules were already studied in detail. The experimental work is accompanied by quantum chemical calculations. Sophisticated and time-consuming studies are planned, but all objectives are achievable.

金属和金属氧化物簇模型对于发展异质催化反应的机械概念非常重要。在室温下已经填充的大量电子激发态的大量EN烯基较低的电子激发态负责簇反应的高反应性和选择性。它允许群集灵活地调整其电子结构，从而理想地与底物分子拟合。除了气相研究外，借助矩阵隔离技术的测量为这一研究主题提供了重要贡献。矩阵 - 隔离技术非常适合研究这些簇的电子激发态的反应性。所有集群首先处于电子基态的基质Garantee的低温（4-40 K）。通过光照射，它们可以选择性地兴奋。 Heidelberg Matrix设备（自制）是专门用于此类实验的。它允许在10-25000 cm-1范围内高分辨率以及发射测量（拉曼和荧光）的吸收测量值（IR和Vis-NIR）。群集可以用狭窄的带宽激光器进行激发。尽管在第一筹期间，工作的主要部分与在其电子基态状态下的群集的表征以及在能量低较低的激发状态下的表征，但第二阶段的工作几乎集中在其电子状态依赖群集的依赖性的依赖性的依赖性。第一个资金期和我们小组的其他结果的结果为这些研究提供了基础。这些物体是氧化钒和氧化钒分子（副氧化物A）以及钛和氧化钛分子（副标理B）。这些分子的电子状态已经进行了详细研究。实验工作伴随着量子化学计算。计划了复杂且耗时的研究，但所有目标都是可以实现的。