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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Understanding the redox properties of dinuclear ruthenium(ii) complexes by a joint experimental and theoretical analysis
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Understanding the redox properties of dinuclear ruthenium(ii) complexes by a joint experimental and theoretical analysis

机译：通过联合实验和理论分析了解双核钌（ii）配合物的氧化还原性质

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摘要

A combined experimental and theoretical approach has been used to investigate the redox properties of two dinuclear Ru(ii) complexes, 2a and 2b, containing the planar dpt-ph-dpt bridging ligand (dpt-ph-dpt = 1′′,4′′-bis(2,4-dipyrid-2′-yl-1,3,5-triazin-6-yl) benzene). The redox properties of the free bridging ligand and the X-ray structure of 2a have also been reported, together with the X-ray structure of a related mononuclear compound, for comparison purposes. The photophysical processes of 2a and 2b have also been studied by pump-probe transient absorption spectroscopy. Compounds 2a and 2b are able to reversibly collect six and eight electrons, respectively, upon electrochemical reduction at mild potentials (>-2.0 V vs. SCE). A detailed assignment of the various reduction processes to specific subunits of the dinuclear arrays has been made possible by calculation of the HOMOs and LUMOs of native and bireduced species. For example, computation allowed us to clarify the redox behavior of 2b: the first reduction processes of this compound occur at almost coincident potentials, with successive electrons added on the same subunit (namely, the bridging ligand). Charge redistribution towards the other subunits of the molecular framework upon second reduction, revealed by calculation performed on the bireduced species, is the key to interpreting this peculiar behavior. Inter-ligand electron hopping interconverts the MLCT state involving the peripheral ligand to that of the (lower-lying) MLCT state that involves the bridging ligand. This process is faster than 350 fs in 2a, where its driving force is higher than 0.2 eV, whereas it occurs with a time constant of about 6 ps in 2b, having a smaller driving force for the process. Both compounds decay to the ground state, with MLCT emission on the nanosecond time scale, however a faster component of such decay is kinetically evidenced, indicating a process of about 200-250 ps in both cases, which is tentatively assigned to relatively slow diffusive solvent dynamics.
机译：已采用实验和理论相结合的方法研究了两个双核Ru（ii）配合物2a和2b的氧化还原特性，它们包含平面dpt-ph-dpt桥联配体（dpt-ph-dpt = 1''，4' '-双（2,4-二吡啶-2'-基-1,3,5-三嗪-6-基）苯）。为了比较目的，也已经报道了游离桥联配体的氧化还原性质和2a的X射线结构，以及相关的单核化合物的X射线结构。还已经通过泵浦探针瞬态吸收光谱法研究了2a和2b的光物理过程。在温和的电势下（> -2.0 V vs. SCE）进行电化学还原后，化合物2a和2b分别能够可逆地收集六个和八个电子。通过计算天然和双还原物种的HOMO和LUMO，可以将各种还原过程详细分配给双核阵列的特定亚基。例如，计算使我们能够澄清2b的氧化还原行为：该化合物的首次还原过程几乎在同时发生的电势下发生，在同一亚基（即桥联配体）上添加了连续电子。通过对二元还原物种进行的计算揭示，第二还原时电荷向分子框架其他亚基的重新分布是解释这种特殊行为的关键。配体间电子跳跃将涉及外围配体的MLCT状态互变为涉及桥接配体的MLCT状态。此过程比2a中的350 fs更快，在2a中其驱动力高于0.2 eV，而在2b中它的时间常数约为6 ps，因此具有较小的驱动力。两种化合物都衰减至基态，MLCT发射在纳秒的时间尺度上，但是从动力学上证明了这种衰减的更快成分，这表明两种情况下的过程约为200-250 ps，暂时分配给了相对较慢的扩散溶剂动力学。

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