Beeston Ruth F., Aldridge W. Stephen, Treadway Joseph A., Fitzgerald Michael C., DeGraff Benjamin A., Stitzel Shannon E.
Department of Chemistry, Davidson College, Davidson, North Carolina 28036.
Inorg Chem. 1998 Aug 24;37(17):4368-4379. doi: 10.1021/ic971322f.
Three hexadentate, podand-type, polypyridyl ligands, (5-bpy-2C)(3)Bz, (4-bpy-2C-Ph)(3)Et, and (4-phen-2C-Ph)(3)Et, and their Ru(II) and Fe(II) complexes have been prepared. Reaction of these ligands with Fe(II) produces only the monometallic hemicage species, while monometallic, bimetallic, and polymetallic Ru(II) complexes are formed. These species are separable by column chromatography, and NMR and ESI mass spectrometry demonstrate that with each ligand the first band to elute corresponds to the monometallic species, RuL. The ESI mass spectra show peaks for RuL and RuL(+) with expected m/z values and isotope peak spacings. (1)H NMR spectroscopy shows that Ru(5-bpy-2C)(3)Bz is trigonally symmetric and contains a rigid methylene bridge between the capping group and the bipyridines. The excited-state lifetimes and emission quantum yields for the hemicage complexes, Ru(5-bpy-2C)(3)Bz, Ru(4-bpy-2C-Ph)(3)Et, and Ru(4-phen-2C-Ph)(3)Et, are significantly enhanced (tau = 2800, 1470, and 3860 ns, and Phi(em) = 0.271, 0.104, 0.202, respectively) relative to the model compounds and to the polymetallic complexes with the same ligand. An Arrhenius fit of temperature-dependent lifetime data for Ru(5-bpy-2C)(3)Bz indicates a high activation energy for crossover to the dd state (DeltaE = 4960 cm(-)(1)) as well as the existence of an additional pathway for deactivation via a "4th MLCT" state. Only after extensive photolysis of Ru(5-bpy-2C)(3)Bz is any decrease in emission intensity observed; this is accompanied by the formation of a bimetallic photoproduct, Ru(2)L(2), with a quantum yield of 7.4 x 10(-)(6). Quenching studies with a variety of quenchers show that the useful excited-state redox and energy-transfer properties characteristic of Ru(II) polypyridyls are retained, but with improved photoinertness and photophysical properties arising from the rigidity of the hemicage complex.
已制备出三种六齿、开链型、多吡啶配体(5 - bpy - 2C)(3)Bz、(4 - bpy - 2C - Ph)(3)Et和(4 - phen - 2C - Ph)(3)Et及其Ru(II)和Fe(II)配合物。这些配体与Fe(II)反应仅生成单金属半笼状物种，而Ru(II)则形成单金属、双金属和多金属配合物。这些物种可通过柱色谱分离，核磁共振和电喷雾电离质谱表明，每种配体洗脱的第一个谱带对应单金属物种RuL。电喷雾电离质谱显示了RuL和RuL(+)的峰，其质荷比和同位素峰间距符合预期。氢核磁共振光谱表明，Ru(5 - bpy - 2C)(3)Bz呈三角对称，在封端基团和联吡啶之间含有一个刚性亚甲基桥。半笼状配合物Ru(5 - bpy - 2C)(3)Bz、Ru(4 - bpy - 2C - Ph)(3)Et和Ru(4 - phen - 2C - Ph)(3)Et的激发态寿命和发射量子产率相对于模型化合物以及具有相同配体的多金属配合物显著提高（分别为τ = 2800、1470和3860 ns，以及Φ(em)=0.271、0.104、0.202）。对Ru(5 - bpy - 2C)(3)Bz的温度依赖寿命数据进行阿仑尼乌斯拟合表明，跃迁到dd态具有较高的活化能（ΔE = 4960 cm(-1)），并且存在通过“第四重配体到金属的电荷转移”态失活的额外途径。只有在对Ru(5 - bpy - 2C)(3)Bz进行广泛光解后，才观察到发射强度有任何降低；这伴随着双金属光产物Ru(2)L(2)的形成，量子产率为7.4×10(-6)。用各种猝灭剂进行的猝灭研究表明，Ru(II)多吡啶所特有的有用的激发态氧化还原和能量转移性质得以保留，但由于半笼状配合物的刚性，其光惰性和光物理性质得到了改善。
