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Spectroscopic Signature of Noncovalent Bonds

非共价键的光谱特征

基本信息

批准号：
1954310
负责人：
Steve Scheiner
金额：
$ 48万
依托单位：
Utah State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-08-15 至 2024-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1954310&HistoricalAwards=false
关键词：
Spectroscopic Signature Noncovalent Bonds

项目摘要

In this project funded by the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program of the Chemistry Division, Professor Steve Scheiner of Utah State University is using modern quantum chemical calculations to predict the way in which the molecular spectra of molecules are affected when two molecules interact with one another in a weak (noncovalent) manner. Chemists and other scientists use different types of spectroscopy to determine the structure and behaviors of atoms and molecules. Infrared spectroscopy (IR) probes the vibrations of molecules, the frequencies of which are specific to a molecule’s geometry and the types of atoms it contains. Nuclear magnetic resonance spectroscopy (NMR) measures the frequencies at which certain atomic nuclei flip direction when exposed to an external magnetic field. In most chemical samples, the molecules of interest are not isolated, but rather moving in the presence of other nearby molecules (especially in the case of liquid and solid samples). Professor Scheiner’s research seeks to uncover how molecules’ interaction with their neighbors changes their vibrational and magnetic properties, and how these changes would show up in IR and NMR spectroscopic measurements. These interactions are called “non-covalent” because they do not involve actual bonding (in other words, sharing of electrons) between neighboring molecules, and are therefore weaker than actual covalent bonds. Yet non-covalent bonds are very important to the structure adopted by many important systems, including proteins, materials, and crystals, some of which are very useful in modern technologies. Quantum calculations are a means of simulating non-covalent interactions and then explaining them in terms of fundamental forces that cause spectroscopic changes. This project involves two graduate students and one undergraduate researcher. The students engaged in this research project are gaining valuable experience in both cutting-edge quantum chemistry and their application to real-world systems. The project focuses on a particular subset of noncovalent bonds, all of them related to the ubiquitous and well-studied H-bonds that have become a mainstay of chemical and biological structure and reactivity. Replacement of the bridging proton of a H-bond by any of a large group of electronegative elements, lead to what have been called halogen, chalcogen, pnicogen, and tetrel bonds, depending upon what family of the periodic table this bridging atom is drawn from. The novelty of these bonds has led to only initial efforts to link their properties and strength to the spectroscopic features, primarily IR and NMR. Complexes of various sorts are being designed that incorporate these types of bonds in a wide variety of systems, spanning a wide range of strength and atom type. Spectra are calculated and compared to other features of the bonding, so as to draw up a set of rules and underlying principles that relate all of these properties to one another. The goal of this project is to develop concepts that will aid experimentalists as they examine their particular systems to understand what interactions are present and which might be influencing the structures. The broader impacts of this work include potential societal benefits from an increased understanding of the forces that control biological and chemical structures, as well as opportunities for the training of students in the application of a range of quantum chemical methods to understand real systems. In addition to the formal research training for students, Prof. Scheiner has developed a course for graduate students and advanced undergraduate designed to introduce both computational and experimentalist students to modern methods of theoretical chemistry. The graduate students working on this CSDM-A project also take part in the instruction ofthis course.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.

在这个由化学学部化学结构、动力学和机制A （CSDM-A）项目资助的项目中，犹他州立大学的Steve Scheiner教授正在使用现代量子化学计算来预测当两个分子以弱（非共价）方式相互作用时分子的分子光谱受到影响的方式。化学家和其他科学家使用不同类型的光谱学来确定原子和分子的结构和行为。红外光谱（IR）探测分子的振动，其频率与分子的几何形状和所含原子的类型有关。核磁共振波谱（NMR）测量某些原子核在暴露于外部磁场时翻转方向的频率。在大多数化学样品中，感兴趣的分子不是孤立的，而是在附近其他分子的存在下移动的（特别是在液体和固体样品的情况下）。Scheiner教授的研究旨在揭示分子与邻居的相互作用如何改变其振动和磁性，以及这些变化如何在红外和核磁共振光谱测量中显示出来。这些相互作用被称为“非共价键”，因为它们不涉及相邻分子之间的实际键合（换句话说，共享电子），因此比实际的共价键弱。然而，非共价键对于许多重要系统所采用的结构是非常重要的，包括蛋白质、材料和晶体，其中一些在现代技术中非常有用。量子计算是一种模拟非共价相互作用的方法，然后用引起光谱变化的基本力来解释它们。该项目涉及两名研究生和一名本科生研究员。参与该研究项目的学生在前沿量子化学及其在现实世界系统中的应用方面获得了宝贵的经验。该项目侧重于非共价键的一个特定子集，所有这些都与普遍存在且研究充分的氢键有关，氢键已成为化学和生物结构和反应性的支柱。氢键的桥接质子被一大群电负性元素中的任何一种取代，形成所谓的卤素键、硫键、磷键和四烷基键，这取决于这个桥接原子来自周期表的哪个族。由于这些化学键的新奇性，人们只能将它们的性质和强度与光谱特征（主要是红外和核磁共振）联系起来。人们正在设计各种各样的配合物，将这些类型的键结合到各种各样的系统中，跨越各种强度和原子类型。计算光谱，并将其与键合的其他特征进行比较，以便制定一套规则和基本原则，将所有这些属性相互联系起来。这个项目的目标是发展一些概念，帮助实验学家检查他们的特定系统，以了解存在哪些相互作用，哪些可能会影响结构。这项工作的更广泛影响包括对控制生物和化学结构的力量的更多理解所带来的潜在社会效益，以及培训学生应用一系列量子化学方法来理解真实系统的机会。除了对学生进行正式的研究培训外，Scheiner教授还为研究生和高级本科生开发了一门课程，旨在向计算和实验型学生介绍理论化学的现代方法。CSDM-A项目的研究生也参与本课程的指导。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。