500 MHz Solid State NMR Spectrometer

固定在表面上的有机金属和有机催化剂的表征极具挑战性，部分原因是催化剂固定在其上的表面的复杂性，部分原因是测量技术的复杂性，这通常需要比基于溶液的样品更先进的设备。固态NMR是表征固体表面上固定化催化剂的最重要的技术之一，因为它使我们能够确定单个活性位点的化学状态，与模型络合物的溶液相数据相比，还可以获得传统液态NMR无法获得的有关固体表面上物种的结构和构象的更多信息。特别是，固态NMR光谱允许我们利用分子间偶极耦合，这在液态NMR中通过分子翻滚来平均。这种偶极耦合可以通过相关光谱法如HETCOR、自旋扩散和TRAPDOR实验定性测量，也可以通过REDOR、SEDOR和POSTC 7光谱法定量测量（以获得原子间距离）。在斯图加特大学的CRC 1333中，24名主要研究人员正在就19个研究课题进行合作，这些课题涉及将固定化有机金属和有机催化剂限制在介孔载体内的影响。限制在约束的几何形状影响催化反应的活性和选择性，迫使活性位点进入新的和更活跃/选择性的构象外的中孔环境。为了充分理解这些效应，活性位点的高质量固态NMR表征至关重要。有必要使用二维（和一维）相关光谱来了解孔中活性位点的二级结构。具体而言，我们建议使用相关方法来理解a）构象几何形状的变化，B）活性位点与孔壁的关联，以及c）附近活性位点彼此之间的紧密关联。这样的测量是不可能与我们目前的核磁共振能力在斯图加特大学。在这个项目中，我们提出了一个新的四通道500 MHz固态NMR光谱仪的收购优化二维相关光谱。有了这个光谱仪，它将有可能了解二级结构，形成内部的孔隙和影响我们的有限的异质化活性位点的催化活性和选择性。如果没有这样的光谱仪，我们将永远无法完全理解为什么限制会影响CRC 1333中研究的催化反应。

Characterization of organometallic and organocatalysts immobilized on surfaces is extremely challenging, owing in part to the complexity of the surfaces on which the catalysts are immobilized and in part to complications in the measurement techniques, which often require more advanced equipment than for solution-based samples. Solid-state NMR is one of the most important techniques for characterizing immobilized catalysts on solid surfaces, because it allows us to determine the chemical state of individual active sites, compared to the solution phase data of the model complexes, and also obtain more information about the structures and conformations of species on solid surfaces not available by traditional liquid state NMR. In particular, solid state NMR spectroscopy allows us to take advantage of intermolecular dipolar coupling, which in liquid state NMR is averaged out by molecular tumbling. Such dipolar coupling can be measured both qualitatively by correlation spectroscopies such as HETCOR, spin diffusion, and TRAPDOR experiments and quantitatively (to get interatomic distances) via methods such as REDOR, SEDOR, and POSTC7 spectroscopies. In the CRC 1333 at the University of Stuttgart, 24 principal investigators are collaborating on 19 research topics concerning the effects of confining immobilized organometallic and organocatalysts inside mesoporous supports. Confinement in the constrained geometries affects both the activity and selectivity of the catalytic reactions by forcing the active sites into new and more active/selective conformations not accessible outside of the mesopore environment. In order to fully understand these effects, high-quality solid-state NMR characterization of the active sites is essential. It is necessary to use 2D (and 1D) correlation spectroscopies to understand the secondary structures of the active sites in the pores. Specifically, we propose to use correlation methods to understand a) changes in conformational geometry, b) association of active sites with the pore wall, and c) close association of nearby active sites with each other. Such measurements are not possible with our current NMR capabilities at the University of Stuttgart. In this project, we propose the acquisition of a new four channel 500 MHz solid-state NMR spectrometer optimized for 2D correlation spectroscopies. With this spectrometer it will be possible to understand the secondary structures that form inside the pores and affect the catalytic activity and selectivity of our confined heterogenized active sites. Without such a spectrometer, we will never be fully able to understand why confinement affects the catalytic reactions studied in the CRC 1333.