Bond Dissociation Energies and Electronic Structure of Small Transition Metal and Lanthanide Molecules

过渡金属和镧系小分子的键解离能和电子结构

• 批准号: 1952924
• 负责人: Michael Morse
• 金额: $ 52.83万
• 依托单位: University of Utah
• 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: 2020-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1952924&HistoricalAwards=false
• 关键词: Bond; Dissociation; Energies; Electronic; Structure

In this project funded by the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program of the Chemistry Division, Professor Michael Morse of the University of Utah is using sophisticated laser techniques to measure the amount of energy that is required to break chemical bonds. The measured bond dissociation energies are key to determining whether a reaction can proceed spontaneously or not. Although some of these bond dissociation energies have been measured previously, the associated measurement errors are quite large. The PI has developed new methods that reduce the measurement errors by factors of 10 to 100, thereby establishing bond dissociation energies to unprecedented accuracy. The species that are amenable to these studies are small molecules containing transition or lanthanide metals, which are particularly difficult to treat by computational methods. The new data obtained by the PI will provide a useful reality check, allowing computational chemists to determine what methods are suitable for modeling of these difficult but important species. The broader impacts of this work include developing a systematic database of bond dissociation energies, providing the data necessary to benchmark computational methods for the transition and lanthanide metals, and providing opportunities for the training of students in the design and construction of advanced experimental instrumentation and spectroscopic data analysis. Students working on these projects develop strong problem-solving skills, which are transferable to many different arenas of scientific endeavor. In an outreach effort to the local community, Dr. Morse continues to give twice-yearly workshops for high school Advanced Placement (AP) chemistry teachers.The project focuses on diatomic and triatomic molecules that possess a high density of electronic states at the ground separated fragment limit. Specific molecules include MX species, where M is an open d-subshell transition metal or lanthanide, and X is a p-block element or ligand, such as B, C, N, O, Si, P, S, Se, F, Cl, Br, CN, or CH. The molecules are formed by laser ablation of the metal in a carrier gas stream containing a source of the ligand. The molecules are cooled by supersonic expansion into vacuum and probed by resonant two- or three-photon ionization schemes. Due to the exceptionally high density of states in these metallic systems, there is a plethora of intersecting potential energy curves at the energy of the ground separated atom limit. When the molecule is excited below this limit, a dense quasicontinuous vibronic spectrum is recorded. When the molecule is excited above the ground separated atom limit, however, spin-orbit and nonadiabatic interactions enable it to hop from curve to curve and find its way to separated atoms on a subnanosecond to few-nanosecond time scale. The abrupt drop in ion signal is readily identified as the bond dissociation energy. In an extension of the method, a cryocooled ion trap photodissociation instrument will be employed, using similar methods to precisely measure bond dissociation energies of metal-containing cations.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.

在这个由化学部化学结构、动力学和机制A （CSDM-A）项目资助的项目中，犹他大学的Michael Morse教授正在使用复杂的激光技术来测量打破化学键所需的能量。测定的键离解能是决定反应能否自发进行的关键。虽然一些键的离解能以前已经测量过，但相关的测量误差相当大。PI开发了新的方法，将测量误差降低了10到100倍，从而以前所未有的精度建立键解离能。适用于这些研究的物种是含有过渡金属或镧系金属的小分子，它们特别难以用计算方法处理。PI获得的新数据将提供一个有用的现实检验，允许计算化学家决定什么方法适合这些困难但重要的物种的建模。这项工作的广泛影响包括建立一个系统的键离解能数据库，为过渡金属和镧系金属的基准计算方法提供必要的数据，并为学生提供设计和构建先进实验仪器和光谱数据分析的培训机会。从事这些项目的学生培养了很强的解决问题的能力，这些能力可以转移到许多不同的科学领域。为了向当地社区伸出援助之手，莫尔斯博士继续每年两次为高中先修课程（AP）化学教师举办研讨会。该项目侧重于双原子和三原子分子，它们在地面分离碎片极限处具有高密度的电子态。特定分子包括MX种，其中M是开d亚壳过渡金属或镧系元素，X是P嵌段元素或配体，如B、C、N、O、Si、P、S、Se、F、Cl、Br、CN或CH。这些分子是在含有配体源的载气流中通过激光烧蚀金属形成的。分子通过超音速膨胀冷却到真空，并通过共振双光子或三光子电离方案进行探测。由于这些金属体系中异常高密度的态，在分离原子极限的能量处有大量相交的势能曲线。当分子被激发到低于这个极限时，一个密集的准连续振动谱被记录下来。然而，当分子被激发到地面分离原子极限以上时，自旋轨道和非绝热相互作用使它能够从一条曲线跳到另一条曲线，并在亚纳秒到几纳秒的时间尺度上找到分离原子的方法。离子信号的突然下降很容易被识别为键解离能。在该方法的扩展中，将使用冷冻离子阱光解离仪，使用类似的方法精确测量含金属阳离子的键解离能。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。

项目成果

Ionization energies and cationic bond dissociation energies of RuB, RhB, OsB, IrB, and PtB

• DOI: 10.1063/5.0107086
• 发表时间: 2022-08-21
• 期刊: JOURNAL OF CHEMICAL PHYSICS
• 影响因子: 4.4
• 作者: Merriles, Dakota M. M.;Morse, Michael D. D.
• 通讯作者: Morse, Michael D. D.

Bond dissociation energies of lanthanide sulfides and selenides

镧系元素硫化物和硒化物的键解离能

• DOI: 10.1063/5.0042695
• 发表时间: 2021
• 期刊: The Journal of Chemical Physics
• 作者: Sorensen, Jason J.;Tieu, Erick;Morse, Michael D.
• 通讯作者: Morse, Michael D.

Bond dissociation energies of diatomic transition metal nitrides

双原子过渡金属氮化物的键解离能

• DOI: 10.1063/5.0141182
• 发表时间: 2023
• 期刊: The Journal of Chemical Physics
• 作者: Merriles, Dakota M.;Knapp, Annie S.;Barrera-Casas, Yexalen;Sevy, Andrew;Sorensen, Jason J.;Morse, Michael D.
• 通讯作者: Morse, Michael D.