Department of Chemistry IFM, University of Turin, Via P. Giuria 7, 10125, Turin, Italy.
Dalton Trans. 2012 Jan 21;41(3):1065-73. doi: 10.1039/c1dt11279a. Epub 2011 Nov 18.
Three new bis-cyclometalated iridium(III) complexes, of general formula Ir(2-phenylpyridine)(2)(L), are reported. The compounds contain a dipyridine-type ligand (L) derived from di-2-pyridylketone (dipyridin-2-ylmethanol, 2,2'-(hydrazonomethylene)dipyridine and 3-hydroxy-3,3-di(pyridine-2-yl)propanenitrile) and were synthesized through two different reaction pathways. The alternative synthetic pathway herein proposed, namely the direct reactions on the complex Ir(2-phenylpyridine)(2)(2,2'-dipyridylketone), overcame the inconveniences encountered with the standard reaction between the dimeric precursor Ir(2-phenylpyridine)(2)(μ-Cl) and the ancillary ligands (L). The photophysical characterization of the iridium complexes reveals that modifications on the ancillary ligand introduce large changes in the photophysical behaviour of the complexes. High emission quantum yield is associated with the presence of a saturated carbon between the two pyridyl moieties: Ir(2-phenylpyridine)(2)(2,2'-dipyridylketone) and Ir(2-phenylpyridine)(2)(2,2'-(hydrazonomethylene)dipyridine) are extremely low emissive, while Ir(2-phenylpyridine)(2)(dipyridin-2-ylmethanol) and Ir(2-phenylpyridine)(2)(3-hydroxy-3,3-di(pyridine-2-yl)propanenitrile) are good photoemitters. DFT and TD-DFT calculations confirmed the mixed LC/MLCT character of the excited states involved in the absorption and emission processes and highlighted the role of the π-conjugation between the two subunits of the ancillary ligand in determining the nature of the LUMO.
报告了三个新的双环金属铱(III)配合物，通式为[Ir(2-苯基吡啶)(2)(L)]+。这些化合物含有一个二吡啶型配体(L)，它来源于二-2-吡啶酮(dipyridin-2-ylmethanol、2,2'-(hydrazonomethylene)dipyridine 和 3-hydroxy-3,3-di(pyridine-2-yl)propanenitrile)，并通过两种不同的反应途径合成。本文提出的替代合成途径是直接在配合物[Ir(2-苯基吡啶)(2)(2,2'-二吡啶酮)]+上进行反应，克服了标准反应中遇到的麻烦，该反应是二聚体前体[Ir(2-苯基吡啶)(2)(μ-Cl)]2与辅助配体(L)之间的反应。铱配合物的光物理特性表明，辅助配体的修饰会使配合物的光物理行为发生很大变化。高发射量子产率与两个吡啶部分之间存在饱和碳原子有关：[Ir(2-苯基吡啶)(2)(2,2'-二吡啶酮)]+和[Ir(2-苯基吡啶)(2)(2,2'-(hydrazonomethylene)dipyridine)]+的发光效率极低，而[Ir(2-苯基吡啶)(2)(二吡啶-2-基甲醇)]+和[Ir(2-苯基吡啶)(2)(3-hydroxy-3,3-di(pyridine-2-yl)propanenitrile)]+则是良好的光发射器。DFT 和 TD-DFT 计算证实了吸收和发射过程中涉及的激发态的混合 LC/MLCT 特征，并强调了辅助配体两个亚基之间的π共轭在决定 LUMO 性质中的作用。
