Ketkov Sergey Yu, Tzeng Sheng-Yuan, Wu Pei-Ying, Markin Gennady V, Tzeng Wen-Bih
G.A. Razuvaev Institute of Organometallic Chemistry RAS, Tropinin St. 49, GSP-445, Nizhny Novgorod, 603950, Russian Federation.
Institute of Atomic and Molecular Sciences, Academia Sinica, 1 Section 4, Roosevelt Road, Taipei, 6017, Taiwan.
Chemistry. 2017 Oct 4;23(55):13669-13675. doi: 10.1002/chem.201702226. Epub 2017 Aug 9.
High-resolution mass-analyzed threshold ionization (MATI) spectra of (η -Ph ) Cr and (η -Ph )(η -PhMe)Cr demonstrate that the Ph groups work as electron donors, decreasing the ionization energy of the gas-phase bisarene complexes. In contrast to electrochemical data, a close similarity of the Ph and Me group effects on the oxidation of free sandwich molecules has been revealed. However, DFT calculations testify for the opposite shifts of the electron density caused by the Me and Ph substituents in the neutral complexes, the latter behaving as an electron-accepting fragment. On the contrary, in the bisarene cations, the Ph group becomes a stronger donor than methyl. This change provides the similar substituent effects observed with the MATI experiment. On the other hand, the well-documented opposite influence of the Me and Ph fragments on the redox potential of the (η -arene) Cr couple in solution appears to be a result of solvation effects but not intramolecular interactions as shown for the first time in this work.
(η⁶ - Ph)₂Cr和(η⁶ - Ph)(η⁶ - PhMe)Cr的高分辨率质量分析阈值电离（MATI）光谱表明，苯基作为电子供体，降低了气相双芳烃配合物的电离能。与电化学数据相反，已揭示出苯基和甲基对游离夹心分子氧化的影响极为相似。然而，密度泛函理论（DFT）计算表明，在中性配合物中，甲基和苯基取代基导致电子密度发生相反的偏移，后者表现为电子接受片段。相反，在双芳烃阳离子中，苯基成为比甲基更强的供体。这种变化导致了MATI实验中观察到的类似取代基效应。另一方面，甲基和苯基片段对溶液中(η⁶ - 芳烃)₂Cr电对氧化还原电位的相反影响，如本工作首次所示，似乎是溶剂化效应而非分子内相互作用的结果。
