Protonation and proton transfer studied with cluster-ion infrared spectroscopy

用簇离子红外光谱研究质子化和质子转移

• 批准号: 0956025
• 负责人: Michael Duncan
• 金额: $ 44.23万
• 依托单位: University of Georgia Research Foundation Inc
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-01 至 2013-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0956025&HistoricalAwards=false
• 关键词: Protonation; proton; transfer; studied; cluster

In this award, funded by the Chemical Structure, Dynamics and Mechanisms Program of the Chemistry Division, and the Office of International Science and Engineering, Professor Duncan frm the University of Georgia will study protonated molecular ion clusters produced in the gas phase as model systems for proton binding and proton transport processes. These processes are central in electrochemistry, in photosynthesis and in the operation of hydrogen fuel cells. The structures of protons attached to key molecules and the bridging structures that are intermediates in proton transfer are the focus of this project. Complexes containing a proton bound to one or more small molecules are produced at low temperature in a molecular beam environment with a pulsed-discharge supersonic nozzle source, so that the intrinsic structures of these systems unperturbed by their environment may be studied. Protonated complexes are size-selected with a mass spectrometer and their structures are investigated with infrared laser spectroscopy. This work focuses on small molecular carbonyls, amino acids and carbocation species, investigating the monomer structures resulting from protonation, their symmetric and asymmetric proton-bound dimer units, and their behavior upon stepwise solvation with water. Using the expanded frequency coverage of new infrared lasers, characteristic vibrational patterns are measured for each molecular unit present, including the critical low frequency region of the spectrum where proton vibrations occur. The shift in vibrational bands for protonated versus free molecules provides a diagnostic for charge-induction effects, while the proton stretching and bending vibrations provide direct access to the proton-transfer potential energy surface. These experiments provide specific new chemical insights about selected proton transfer reactions. They also produce benchmark data for comparison to the results of computational quantum chemistry which attempts to calculate proton transfer dynamics. Vibrational signatures measured for protonated organic molecules known as carbocations may be useful for infrared astronomy of interstellar gas clouds. Equally important is the training of undergraduates, graduate students and postdoctoral fellows in the methods, techniques and instrumentation of modern physical chemistry. Ongoing collaborations include a non-Ph.D. granting institution (Kennesaw State University) and two international labs (Chemistry Dept., Nottingham, UK and Fritz Haber Institute, Berlin).

在这个由化学系化学结构、动力学和机制项目和国际科学与工程办公室资助的奖项中，来自格鲁吉亚大学的邓肯教授将研究在气相中产生的质子化分子离子簇，作为质子结合和质子传输过程的模型系统。这些过程在电化学、光合作用和氢燃料电池的操作中是中心的。 本研究的重点是质子在关键分子上的结构和质子转移中间体的桥连结构。 在低温下，在具有脉冲放电超音速喷嘴源的分子束环境中，产生含有与一个或多个小分子结合的质子的络合物，从而可以研究这些系统不受其环境干扰的内在结构。 质子化配合物的大小选择与质谱仪和它们的结构进行了研究与红外激光光谱。 这项工作的重点是小分子羰基化合物，氨基酸和碳正离子物种，调查质子化产生的单体结构，它们的对称和不对称质子结合的二聚体单元，以及它们的行为逐步溶剂化与水。 使用新的红外激光器的扩展的频率覆盖范围，测量存在的每个分子单元的特征振动模式，包括质子振动发生的光谱的临界低频区域。 质子化分子与自由分子的振动带的位移提供了电荷诱导效应的诊断，而质子拉伸和弯曲振动提供了直接进入质子转移势能面的途径。 这些实验提供了特定的质子转移反应的新的化学见解。 他们还产生基准数据，用于与试图计算质子转移动力学的计算量子化学的结果进行比较。 测量质子化的有机分子碳正离子的振动特征可能对星际气体云的红外天文学有用。同样重要的是对本科生、研究生和博士后研究员进行现代物理化学方法、技术和仪器方面的培训。正在进行的合作包括一个非博士。授予机构（肯尼索州立大学）和两个国际实验室（化学系，诺丁汉，英国和弗里茨哈伯研究所，柏林）。