Reactive Systems at the Onset of Microsolvation

摘要建议：CHE-0132584 PI：Leopold，Kenneth R.溶剂化对分子结构和反应性的影响是化学中的一个重要问题。微溶剂化物种的研究提供了一个有价值的手段，桥接气相测量与凝聚态物质的研究。这些工作提供了发展一个越来越准确的分子水平的描述溶剂化的可能性。在本计画中，转动光谱将被用来研究微溶剂化对反应性酸碱复合物的影响。分子结构和偶极矩将分别由转动常数和斯塔克效应数据确定。在某些情况下，电荷分布的各个方面也将通过核超精细结构来揭示。两类系统是有针对性的：（i）部分结合的刘易斯酸-碱络合物，其结构和键结在结晶时发生显着变化，和（ii）氢键系统，在溶液中或在结晶相中进行质子转移。选择这些系统是因为在这两种情况下，聚集促进化学变化和微溶剂化的影响，因此，预计将是显着的。在这项工作中要解决的中心问题是，“在聚集驱动化学变化的系统中，第一近邻的影响有多大？".也被认为是几个系统的溶剂化程度较高。这项工作将系统地利用这些反应性的酸碱复合物的超敏反应，他们的近邻相互作用的目的，调查“溶剂化”的影响，在小集群的水平。例如，生物的化学反应、受污染的地下沃茨中的反应，甚至许多重要的工业过程，都只有在分子溶解在溶剂中时才能发生。当这种反应发生时，溶剂本身并不是化学反应的直接参与者，尽管越来越清楚的是，它的存在可以在介导发生的反应中发挥重要作用。因此，在这个项目中，我们有兴趣研究溶剂在介导化学过程中的作用。我们的方法是通过研究接近一对反应分子的单个溶剂分子的影响来获得对问题的基本理解。为了实现这一点，我们分离出两个反应分子，加上一个溶剂分子，并使用微波来研究溶剂如何影响它们。了解单个溶剂分子的影响是重要的一步，因为它是了解真实的溶液中存在的许多溶剂分子的影响的基本构建块。此外，从这项工作中获得的基本知识可能对模拟具有社会重要性的困难问题产生直接影响，例如，地球大气中粒子的形成，其存在对气候、臭氧水平和人类健康有广泛影响。通过这种方式，我们设想了本项目中所涉及的基础科学的潜在实际应用。明尼苏达大学的研究生将参加这项研究，作为他们攻读博士学位培训的一部分，并将学习适用于各种问题的许多技术技能。

AbstractProposal: CHE-0132584PI: Leopold, Kenneth R.The effect of solvation on molecular structure and reactivity is an important problem in chemistry. The investigation of microsolvated species offers a valuable means of bridging gas phase measurements with studies of condensed matter. Such work offers the possibility of developing an increasingly accurate molecular-level description of solvation. In this project, rotational spectroscopy will be used to examine the effects of microsolvation on reactive acid-base complexes. Molecular structures and dipole moments will be determined from rotational constants and Stark effect data, respectively. Aspects of charge distribution will, in certain cases, also be revealed by nuclear hyperfine structure. Two classes of systems are targeted: (i) partially bound Lewis acid-base complexes, whose structure and bonding change dramatically upon crystallization and (ii) hydrogen bonded systems which undergo proton transfer in solution or in the crystalline phase. These systems are chosen because in both cases, aggregation promotes chemical change and the effects of microsolvation are, therefore, expected to be pronounced. The central question to be addressed in this work is , "In systems for which aggregation drives chemical change, how big is the effect of the first near neighbor?". Several systems with higher degrees of solvation are also considered. This work will systematically exploit the hypersensitivity of these reactive acid-base complexes to their near-neighbor interactions for the purpose of investigating "solvation" effects at the small cluster level.Much of the chemistry important to human activity involves substances in solution. For example, the chemistry of living things, reactions in contaminated ground waters, and even a host of important industrial processes occur only when molecules are dissolved in a solvent. When such reactions occur, the solvent itself is not a direct participant in the chemistry, though it has become increasingly clear that its presence can play a significant role in mediating the reactions that take place. Thus, in this project, we are interested in studying the role of solvent in mediating chemical processes. Our approach is to gain a basic understanding of the problem by examining the effect of a single solvent molecule close to a pair of reactive molecules. To accomplish this, we isolate two reacting molecules, plus one solvent molecule, and use microwaves to investigate how the solvent affects them. Understanding the influence of a single solvent molecule is an important step, as it is the fundamental building block for understanding the influence of the many solvent molecules present in a real solution. Moreover, the basic knowledge gained from this work may have direct consequences for modeling difficult problems of societal importance, e.g., the formation of particles in the earth's atmosphere, whose presence has wide ranging effects on climate, ozone levels, and human health. In this way, we envision potential practical applications for the fundamental science addressed in this project. Graduate students at the University of Minnesota will participate in this research as part of their training toward the doctoral degree and will learn numerous technical skills applicable to a wide variety of problems.