EAGER: Three-wave mixing techniques to study and utilize nuclear quadrupole coupling effects in chiral molecules

自然界中的许多分子，特别是生物分子，在它们的几何结构中表现出手性。 这就是说，两个分子可以有相同数量和种类的原子和几何排列，但它们是彼此的镜像，就像一个人的左手和右手一样。 这种化学上的“手性”被称为“手性”。在化学测量中，区分“手”-称为对映异构体-并量化每一种的量可能是一个困难的技术挑战。 这种困难会限制我们合成和分离给定对映体的能力。在该项目中，由化学部的化学结构、动力学和机理（CSDM-A）和化学测量和成像（CMI）计划资助，密苏里州科技大学的Garry Grubbs II教授使用先进的微波光谱技术来确定样品中存在的对映体的类型和浓度。微波光谱学根据微波辐射使分子旋转的速度提供有关分子结构的信息。 Grubbs教授假设，如果一个分子包含一个非常重的原子，如溴或碘，那么这个分子的“手性”就可以被确定。 这些重原子的原子核含有电荷的排列，可以使整个分子的旋转在微波实验中比在其他情况下更多地揭示其结构。 如果Grubbs教授的假设是正确的，可能会有新的途径来更快，更准确地合成和监测手性系统，这对制药研究特别重要。该项目还使用最先进的仪器设计以及新的量子理论发展来培训研究生，目前尚未探索的物理化学领域。该项目的重点是利用最新发现的手性体系中的微波三波混频对核电四极耦合相互作用。这些实验的目的是建立，第一次，实验数据和理论理解的核自旋为基础的方法，用于识别和量化混合物中的对映体物种。微波三波混频涉及利用旋转跃迁，其涉及沿沿着两个分子轴激发，同时沿沿着第三轴检测，从而产生与三能级脉泽系统非常相似的闭环跃迁能量路径。电偶极禁戒，四极促进过渡时发生的非对角核电四极相互作用的分子旋转常数的顺序，并遵循相同的闭环路径。然后使用微波三波混频来利用这些，因为该技术对相位而不是传统微波光谱的能量敏感，从而首次在单一实验中确定非对角符号以及洞察所讨论的对映异构体。同位素替代谱分析验证了实验结果的准确性。 除了技术和教育的影响，这项研究可能会扩大的范围，并提供分子信息，微波spectroscopy.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的知识价值和更广泛的影响审查标准的支持。

Many molecules in nature, particularly biological molecules, exhibit a handedness in their geometric structure. This is to say two molecules can have the same number and kinds of atoms and geometric arrangement, but they are mirror images of each other, as are one's left and right hands. This "handedness" in chemistry is referred to as "chirality." In chemical measurements, distinguishing between the "hands"- known as enantiomers- and quantifying the amounts of each can be a difficult technological challenge. This difficulty can limit our ability to synthesize and separate a given enantiomer. In this project, funded by the Chemical Structure, Dynamics, and Mechanism (CSDM-A) and Chemical Measurement and Imaging (CMI) Programs of the Chemistry Division, Professor Garry Grubbs II of the Missouri University of Science and Technology is using advanced microwave spectroscopy techniques to determine the type and concentration of enantiomers present in a sample. Microwave spectroscopy provides information about molecular structure based on how fast they can be made to rotate by the microwave radiation. Professor Grubbs hypothesizes that "handedness" of a molecule can be determined if that molecule contains a very heavy atom like bromine or iodine. The nuclei of these heavy atoms contain arrangements of electrical charge that can make the rotations of the overall molecule reveal more about its structure in a microwave experiment than it would otherwise. If Professor Grubbs' hypothesis is correct, there may be new paths toward faster and more accurate synthesis and monitoring of chiral systems, which is particularly important to pharmaceutical research. The project is also training graduate students in currently unexplored areas of physical chemistry using state-of-the-art instrument design as well as new quantum theory development.This project focuses on utilizing the recent discovery of microwave three-wave mixing in chiral systems on nuclear electric quadrupole coupling interactions. These experiments are designed to establish, for the first time, experimental data and theoretical understanding for nuclear spin-based methodologies for identifying and quantifying enantiomeric species in mixtures. Microwave three-wave mixing involves utilizing rotational transitions involving excitation along two molecular axes while detecting along the third axis, creating closed-loop transition energy pathways very similar to a three-level maser system. Electric dipole-forbidden, quadrupole-facilitated transitions occur when off-diagonal nuclear electric quadrupole interactions are on the order of the molecular rotation constants and follow the same closed-loop pathway. These are then leveraged using microwave three-wave mixing because of the technique's sensitivity to phase rather than energy of traditional microwave spectroscopy, allowing for the determination of the off-diagonal sign in a singular experiment for the first time as well as insight into the enantiomer in question. Isotopic substitution spectra analysis are then used to validate the veracity of the experimental results. In addition to the technological and educational impacts, this research may expand the reach of, and molecular information offered from, microwave spectroscopy.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.