Marks Joshua H, Batchelor Anna G, Blais John R C, Duncan Michael A
Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States.
J Phys Chem A. 2022 Jul 7;126(26):4230-4240. doi: 10.1021/acs.jpca.2c03035. Epub 2022 Jun 24.
Ion-molecule complexes of uranium or thorium singly-charged positive ions bound to cyclooctatetraene (COT), i.e., M(COT), are produced by laser ablation and studied with UV laser photodissociation. The ions are selected by mass and excited at 355 or 532 nm, and the ionized dissociation products are detected using a reflectron time-of-flight mass spectrometer. The abundant fragments M(CH), M(CH), and M(CH) occur for complexes of both metals, whereas the M(CH), M(CH), and M(CH) fragments are prominent for uranium complexes but not for thorium. Additional experiments investigate the dissociation of M(benzene) ions which may be intermediates in the fragmentation of the COT ions. The experiments are complemented by computational quantum chemistry to investigate the structures and energetics of fragment ions. Various cation-π and metallacycle structures are indicated for different fragment ions. The metal ion-ligand bond energies for corresponding complex ions are systematically greater for the thorium species. The computed thermochemistry makes it possible to explain the mechanistic details of the photochemical fragmentation processes and to reveal new actinide organometallic structures.
通过激光烧蚀产生与环辛四烯（COT）结合的铀或钍单电荷正离子的离子 - 分子络合物，即M（COT），并用紫外激光光解离进行研究。离子通过质量筛选，并在355或532nm处激发，使用反射式飞行时间质谱仪检测电离解离产物。两种金属的络合物都会产生丰富的碎片M(CH)、M(CH)和M(CH)，而M(CH)、M(CH)和M(CH)碎片在铀络合物中很突出，但在钍络合物中不突出。额外的实验研究了M(苯)离子的解离，M(苯)离子可能是COT离子碎片化过程中的中间体。通过计算量子化学对实验进行补充，以研究碎片离子的结构和能量学。不同的碎片离子显示出各种阳离子 - π和金属环结构。对于相应的络合离子，钍物种的金属离子 - 配体键能系统地更高。计算出的热化学使得解释光化学碎片化过程的机理细节并揭示新的锕系有机金属结构成为可能。
