Photofragmentation of Gas-Phase Lanthanide Cyclopentadienyl Complexes: Experimental and Time-Dependent Excited-State Molecular Dynamics

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• 作者：Jiangchao Chen ; Andrew M. Hochstatter ; Dmitri Kilin ; P. Stanley May ; Qingguo Meng ; Mary T. Berry
• 刊名：Organometallics
• 出版年：2014
• 出版时间：April 14, 2014
• 年：2014
• 卷：33
• 期：7
• 页码：1574-1586
• 全文大小：773K
• 年卷期：v.33,no.7(April 14, 2014)
• ISSN：1520-6041

文摘

Unimolecular gas-phase laser-photodissociation reaction mechanisms of open-shell lanthanide cyclopentadienyl complexes, Ln(Cp)<sub>3sub> and Ln(TMCp)<sub>3sub>, are analyzed from experimental and computational perspectives. The most probable pathways for the photoreactions are inferred from photoionization time-of-flight mass spectrometry (PI-TOF-MS), which provides the sequence of reaction intermediates and the distribution of final products. Time-dependent excited-state molecular dynamics (TDESMD) calculations provide insight into the electronic mechanisms for the individual steps of the laser-driven photoreactions for Ln(Cp)<sub>3sub>. Computational analysis correctly predicts several key reaction products as well as the observed branching between two reaction pathways: (1) ligand ejection and (2) ligand cracking. Simulations support our previous assertion that both reaction pathways are initiated via a ligand-to-metal charge-transfer (LMCT) process. For the more complex chemistry of the tetramethylcyclopentadienyl complexes Ln(TMCp)<sub>3sub>, TMESMD is less tractable, but computational geometry optimization reveals the structures of intermediates deduced from PI-TOF-MS, including several classic 鈥渢uck-in鈥?structures and products of Cp ring expansion. The results have important implications for metal鈥搊rganic catalysis and laser-assisted metal鈥搊rganic chemical vapor deposition (LCVD) of insulators with high dielectric constants.