Quantitative characterization of weak interactions

通过这个奖项，由化学系的化学结构，动力学和机制计划资助，教授A。来自托莱多大学的Alan Pinkerton和Elizabeth Zhurova博士将使用先进的高分辨率X射线晶体学技术定量表征固态原子或分子之间的重要弱相互作用。 电子密度分布将由单晶散射的X射线强度确定，并通过将原子中心多极展开的参数拟合到观察到的数据来量化。一系列的内部和分子间的相互作用，以前已确定的结构数据，许多“非键合”的距离显着低于货车范德华半径的总和，将进行研究。目前，已经确定了20种不同分子固体中20种不同原子对之间的潜在相互作用。这项研究的信息将为材料设计/晶体工程和生物配体-受体结合/细胞信号传导等广泛的科学领域提供新的见解。所有材料的性质都与原子和分子之间的电子分布密切相关。 例如，金刚石和石墨完全由碳原子组成，但具有截然不同的性质，金刚石非常坚硬，而石墨是软润滑剂。 这很容易理解，因为金刚石中电子的分布导致三维中的强共价键，而石墨在二维中是强键合的，而在三维中是弱键合的。强化学键的重要性已经被几代化学家所认识，它们的理论和实验表征是教科书的素材。 弱相互作用的重要性，除了氢键，还没有系统地研究使用X射线衍射技术，直到现在，代表了一个新的研究方向在化学。这一追求将使研究生和博士后获得低温学和高分辨率X射线晶体学的专业培训。低温数据收集和分析的新方法，以及随后培训其他人的研讨会，将推动实验可获得的极限。该项目还将被纳入一个推广计划，向高中生介绍结晶学科学。

Through this award, funded by the Chemical Structure, Dynamics, and Mechanisms Program of the Division of Chemistry, Prof. A. Alan Pinkerton and Dr. Elizabeth Zhurova from the University of Toledo, will quantitatively characterize important weak interactions between atoms or molecules in the solid state using advanced, high resolution, X-ray crystallographic techniques. The electron density distribution will be determined from the intensities of the X-rays scattered from single crystals, and quantified by fitting the parameters of an atom-centered multipole expansion to the observed data. A range of intra- and inter-molecular interactions that have been previously identified from structural data, many with "non-bonded" distances significantly below the sum of the Van der Waals radii, will be studied. Currently potential interactions between 20 different atom pairs have been identified for 20 different molecular solids. Information from this study will provide new insight into a wide spectrum of scientific areas such as materials design/crystal engineering and biological ligand-receptor binding/cell signaling. Properties of all materials are intimately related to the distribution of electrons between the atoms and molecules. For example, diamond and graphite are composed entirely of carbon atoms, but have vastly different properties, diamond being very hard, and graphite being a soft lubricant. This is easily understood as the distribution of electrons in diamond leads to strong covalent bonds in three dimensions, whereas graphite is strongly bonded in two dimensions, and weakly bonded in the third. The importance of strong chemical bonds has been recognized by generations of chemists, and their characterization by theory and experiment is the material for text books. The importance of weak interactions, with the exception of hydrogen bonds, has not been systematically studied using X-ray diffraction techniques until now, and represents a new investigative direction in chemistry. This pursuit will allow graduate students and postdoctoral fellows to acquire specialized training in cryogenics, and in high resolution X-ray crystallography. The new methods for cryogenic data collection and analysis, followed by workshops to train others, will push the limits of what is experimentally obtainable. This project will also be integrated into an outreach program to introduce high school students to the science of crystallography.