Roy Michael D, Trenerry Michael J, Thakuri Biswash, MacMillan Samantha N, Liptak Matthew D, Lancaster Kyle M, Berry John F
Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States.
Department of Chemistry, University of Vermont, Burlington, Vermont 05405, United States.
Inorg Chem. 2022 Feb 28;61(8):3443-3457. doi: 10.1021/acs.inorgchem.1c03346. Epub 2022 Feb 17.
Diruthenium paddlewheel complexes supported by electron-rich anilinopyridinate (Xap) ligands were synthesized in the course of the first in-depth structural and spectroscopic interrogation of monocationic [Ru(Xap)Cl] species in the Ru oxidation state. Despite paramagnetism of the compounds, H NMR spectroscopy proved highly informative for determining the isomerism of the Ru and Ru compounds. While most compounds are found to have the polar (4,0) geometry, with all four Xap ligands in the same orientation, some synthetic procedures resulted in a mixture of (4,0) and (3,1) isomers, most notably in the case of the parent compound Ru(ap)Cl. The isomerism of this compound has been overlooked in previous reports. Electrochemical studies demonstrate that oxidation potentials can be tuned by the installation of electron donating groups to the ligands, increasing accessibility of the Ru oxidation state. The resulting Ru monocations were found to have the expected (π*) ground state, and an in-depth study of the electronic transitions by Vis/NIR absorption and MCD spectroscopies with the aid of TD-DFT allowed for the assignment of the electronic spectra. The empty δ* orbital is the major acceptor orbital for the most prominent electronic transitions. Both Ru and Ru compounds were studied by Ru K-edge X-ray absorption spectroscopy; however, the rising edge energy is insensitive to redox changes in the compounds due to the broad line shape observed for 4d transition metal K-edges. DFT calculations indicate the presence of ligand orbitals at the frontier level, suggesting that further oxidation beyond Ru will be ligand-centered rather than metal-centered.
在对处于钌氧化态的单阳离子[Ru(Xap)Cl]物种进行首次深入的结构和光谱研究过程中，合成了由富电子苯胺基吡啶（Xap）配体支撑的二钌桨轮配合物。尽管这些化合物具有顺磁性，但1H NMR光谱对于确定Ru和Ru化合物的异构现象极具信息价值。虽然发现大多数化合物具有极性（4,0）几何结构，即所有四个Xap配体处于相同取向，但一些合成方法会导致（4,0）和（3,1）异构体的混合物，最显著的是在母体化合物Ru(ap)Cl的情况下。该化合物的异构现象在先前的报告中被忽视了。电化学研究表明，通过在配体上安装供电子基团可以调节氧化电位，从而增加Ru氧化态的可达性。发现所得的Ru单阳离子具有预期的（π*）基态，并且借助TD-DFT通过可见/近红外吸收和MCD光谱对电子跃迁进行的深入研究使得能够对电子光谱进行归属。空的δ*轨道是最显著电子跃迁的主要受体轨道。对Ru和Ru化合物都进行了Ru K边X射线吸收光谱研究；然而，由于在4d过渡金属K边观察到的宽线形状，上升边能量对化合物中的氧化还原变化不敏感。DFT计算表明在前沿能级存在配体轨道，这表明超过Ru的进一步氧化将以配体为中心而非以金属为中心。
