Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University of Mainz, Duesbergweg 10-14, 55128 Mainz, Germany.
Inorg Chem. 2013 Feb 4;52(3):1248-64. doi: 10.1021/ic301632y. Epub 2013 Jan 11.
New cationic metallo ligands L1-L3 based on bis(terpyridine) ruthenium(II) complexes decorated with differently substituted 2,2'-bipyridines attached via amide groups (5-NHCO-bpy, 4-CONH-bpy, 5-CONH-bpy) were prepared. Coordination of Re(I)Cl(CO)(3) fragments to the bpy unit gives the corresponding bimetallic Ru~Re complexes 1-3. Hydrogen bonds of the bridging amide groups to PF(6) counterions or to water molecules are observed both in the solid state and in solution. The impact of the amide orientation, the connecting site, and the coordination of counterions on redox and photophysical properties is explored. Both the metallo ligands L1-L3 and the bimetallic complexes 1-3 are emissive at room temperature in fluid solution. The emission originates from (3)MLCT(Ru) states in all cases. Accordingly, the first oxidation of L1-L3 and 1-3 to L1-L3 and 1-3 is assigned to the Ru(II/III) couple, while the first reduction to L1-L3 and 1-3 occurs at the tpy-CO ligand as shown by UV/vis, IR, and EPR spectroscopy of the chemically generated radicals. Under rapid freezing conditions, radicals 2 and 3 are stabilized as different valence isomers with the odd electron localized at the bpy-CO bridging unit instead of the tpy-CO. Furthermore, in radical 3 this valence equilibrium is shifted from bpy-CO to tpy-CO by coordination of PF(6) counterions to the bridging amide unit and back by replacing the PF(6) counterion with BPh(4). Photoinduced electron transfer (λ(exc) = 500 nm) to L1-L3 and to 1-3 is successful using triethanolamine (TEOA) as a reducing agent. Photocatalytic reduction of CO(2) by TEOA and 1-3 is hampered by the wrong site of electron localization in the one-electron reduced species 1-3.
基于双（三联吡啶）钌（II）配合物的新型阳离子金属配合物 L1-L3 被制备，其通过酰胺基团（5-NHCO-bpy、4-CONH-bpy、5-CONH-bpy）修饰，连接了不同取代的 2,2'-联吡啶。[Re（I）Cl（CO）（3）] 片段与 bpy 单元的配位给出了相应的双金属 Ru~Re 配合物 1-3。在固态和溶液中都观察到桥接酰胺基团的氢键与 PF6抗衡离子或水分子相互作用。研究了酰胺取向、连接位置以及抗衡离子的配位对氧化还原和光物理性质的影响。金属配体 L1-L3 和双金属配合物 1-3 在室温下在流体溶液中均具有发光性。发射源于所有情况下的（3）MLCT（Ru）态。相应地，L1-L3 和 1-3 的第一次氧化为 L1-L3和 1-3被分配到 Ru(II/III)对，而第一次还原为 L1-L3和 1-3发生在 tpy-CO 配体上，如通过 UV/vis、IR 和 EPR 光谱检测化学生成的自由基所示。在快速冷冻条件下，自由基2和3被稳定为不同价态的异构体，奇数电子定位于 bpy-CO桥接单元而不是 tpy-CO。此外，在自由基3中，通过与桥接酰胺单元配位，抗衡离子PF6和通过用BPh4取代PF6，这种价平衡从 bpy-CO转移到tpy-CO。使用三乙醇胺（TEOA）作为还原剂，成功地将电子转移到 L1-L3 和 1-3 上（λ（ex）= 500nm）。光催化还原 CO2 被 TEOA 和 1-3 阻碍，因为在单电子还原物种1-3中电子定位在错误的位置。
