Strongly Phosphorescent Palladium(II) Complexes of Tetradentate Ligands with Mixed Oxygen, Carbon, and Nitrogen Donor Atoms: Photophysics, Photochemistry, and Applications
Strongly Phosphorescent Palladium(II) Complexes of Tetradentate Ligands with Mixed Oxygen, Carbon, and Nitrogen Donor Atoms: Photophysics, Photochemistry, and Applications
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DOI：
10.1002/anie.201305590
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发表时间：
2013-11-04
影响因子：
16.6
通讯作者：
Che, Chi-Ming
中科院分区：
文献类型：
--
作者：
Chow, Pui Keong;Ma, Chensheng;Che, Chi-Ming
在室温下，在溶液中表现出强磷光的过渡金属配合物通常含有RuII、OsII、IrIII或PtII离子，但发光的AuIII配合物[1]也得到了越来越多的研究。与大量关于发光PtII配合物的文献相比，含有非卟啉配体且具有良好发射量子产率（Fem）的发光PdII配合物的例子很少这种长期存在的情况的关键在于PdII离子明显较低的配体场分裂因此，PdII配合物的金属中心d-d态总是热可及的，这使得反键4dx2Ày2轨道易于占据，从而通过严重的激发态结构畸变导致有效的非辐射衰变。抑制d-d失活的一种策略是使用强场配体，从而将d-d态提高到更高的能量。虽然许多双齿和三齿螯合配体，如C-去质子化的C^ N和C^ N^ N （HC^ N= 2-苯基吡啶；HC^ N^ N= 6-苯基- 2,2 ' -联吡啶）配体可以得到发光PtII配合物，但它们对设计发光PdII配合物并不有效。大多数报道的含有非卟啉配体的发光PdII配合物在低温（77 K）[4]时仅弱发射（Fem< ca. 10À2），在室温下溶液中不发射（Fem< ca. 10À4）。[3]磷光PdII复合物的著名例子包括PdII -卟啉复合物
Transition-metal complexes that show strong phosphorescence in solution at room temperature usually contain a RuII, OsII, IrIII, or PtII ion, but luminescent AuIII complexes [1] have also been studied increasingly. In contrast to the extensive literature on luminescent PtII complexes,[2] examples of luminescent PdII complexes that contain non-porphyrin ligands and show decent emission quantum yields (Fem) are sparse.[3] The crux of this long-standing situation lies in the significantly lower ligand-field splitting of the PdII ion.[4] Accordingly, the metal-centered d–d states of PdII complexes are always thermally accessible, which enables facile population of the antibonding 4dx2Ày2 orbital and hence leads to effective nonradiative decay through severe excited-state structural distortion.A strategy for suppression of the d–d deactivation is to use strong-field ligands so as to raise the d–d states to a higher energy. Although many bidentate and tridentate chelating ligands, such as C-deprotonated C^ N and C^ N^ N (HC^ N= 2-phenylpyridine; HC^ N^ N= 6-phenyl-2, 2’-bipyridine) ligands, give luminescent PtII complexes, they are not effective for the design of luminescent PdII complexes. Most of the reported luminescent PdII complexes containing non-porphyrin ligands are only weakly emissive (Fem< ca. 10À2) at low temperature (77 K)[4] and non-emissive (Fem< ca. 10À4) in solution at room temperature.[3] Notable examples of phosphorescent PdII complexes include PdII–porphyrin complexes