Bis-Ferrocenyl-Pyridinediimine Trinuclear Mixed-Valent Complexes with Metal-Binding Dependent Electronic Coupling: Synthesis, Structures, and Redox-Spectroscopic Characterization,Journal of the American Chemical Society

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Bis-Ferrocenyl-Pyridinediimine Trinuclear Mixed-Valent Complexes with Metal-Binding Dependent Electronic Coupling: Synthesis, Structures, and Redox-Spectroscopic Characterization
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-10-16 , DOI: 10.1021/jacs.0c10015
Cole Carter ₁ , Yosi Kratish ₁ , Titel Jurca ₁ , Yanshan Gao ₁ , Tobin J. Marks ₁

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A family of metal dichloride complexes having a bis-ferrocenyl-substituted pyridinediimine ligand was systematically synthesized ((Fc2PDI)MCl2, M = Mg, Zn, Fe, and Co) and characterized crystallographically, spectroscopically, electrochemically, and computationally. Electronic coupling between the ligand ferrocene units is switched on upon binding to a MCl2 fragment, as evidenced by both sequential oxidation of the ferrocenes in cyclic voltammetry (ΔEox ≈ 200 mV) and by Inter-Valence Charge Transfer electronic excitations in the near IR. Additionally, UV-vis spectra are used to directly observe orbital mixing between the ferrocenyl units and the imine π system since breaking of the orbital symmetry results in allowed transitions (ϵ = 2800 M-1cm-1 vs ϵ ≈ 200 M-1cm-1 in free ferrocene) as well as broadening and red-shifting of the ferrocenyl transitions-indicating organic character in formerly pure metal-centered transitions. DFT analysis reveals that interaction between the ferrocenes and the MCl2 fragment is small and suggests that communication is mediated by better energy matching between the ferrocene and organic π* orbitals upon coordination, allowing superexchange coupling through the LUMO. Furthermore, single crystal diffraction data obtained from oxidation of one and both ferrocenes show distortions, introducing the empty dxy/dx2-y2 orbitals into the secondary coordination sphere of the MCl2 fragment. Such structural rearrangements are infrequent in ferrocenyl mixed-valent compounds, and implications for catalysis as well as electronic communication are discussed.

中文翻译：

具有金属结合依赖性电子耦合的双二茂铁基吡啶二亚胺三核混合价配合物：合成、结构和氧化还原光谱表征

系统合成了一系列具有双二茂铁基取代的吡啶二亚胺配体的金属二氯化物配合物 ((Fc2PDI)MCl2，M = Mg、Zn、Fe 和 Co)，并在晶体学、光谱学、电化学和计算方面进行了表征。配体二茂铁单元之间的电子耦合在与 MCl2 片段结合时开启，这可以通过循环伏安法中二茂铁的顺序氧化 (ΔEox ≈ 200 mV) 和近红外中的价间电荷转移电子激发来证明。此外，UV-vis 光谱用于直接观察二茂铁单元和亚胺 π 系统之间的轨道混合，因为轨道对称性的破坏导致允许的跃迁（ϵ = 2800 M-1cm-1 vs ϵ ≈ 200 M-1cm-1 in free二茂铁）以及二茂铁基跃迁的加宽和红移——表明以前纯金属中心跃迁中的有机特征。DFT 分析表明，二茂铁和 MCl2 片段之间的相互作用很小，表明通讯是由二茂铁和有机 π* 轨道在协调时更好的能量匹配介导的，允许通过 LUMO 进行超交换耦合。此外，从一种和两种二茂铁氧化获得的单晶衍射数据显示失真，将空的 dxy/dx2-y2 轨道引入 MCl2 碎片的二级配位球。这种结构重排在二茂铁基混合价化合物中很少见，并讨论了对催化和电子通讯的影响。

更新日期：2020-10-16

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