Dipyridylketone as a versatile ligand precursor for new cationic heteroleptic cyclometalated iridium complexes
作者:Giorgio Volpi、Claudio Garino、Emanuele Breuza、Roberto Gobetto、Carlo Nervi
DOI:10.1039/c1dt11279a
日期:——
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)]2 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.
报告了通式为[Ir(2-苯基吡啶)2(L)]+的三种新的双环甲基化铱(III)配合物。这些化合物含有从二-2-吡啶基酮(二吡啶-2-基甲醇、2,2′-(肼基亚甲基)二吡啶和 3-羟基-3,3-二(吡啶-2-基)丙腈)衍生的二吡啶型配体(L),并通过两种不同的反应途径合成。本文提出的另一种合成途径,即[Ir(2-苯基吡啶)2(2,2′-二吡啶基酮)]+复合物的直接反应,克服了二聚前体[Ir(2-苯基吡啶)2(μ-Cl)]2和辅助配体(L)之间的标准反应所遇到的不便。铱配合物的光物理特性分析表明,对辅助配体的修饰会使配合物的光物理特性发生巨大变化。高发射量子产率与两个吡啶基之间存在饱和碳有关:[Ir(2-苯基吡啶)2(2,2′-二吡啶基酮)]+ 和 [Ir(2-phenylpyridine)2(2,2′-(hydrazonomethylene)dipyridine)]+ 的发射率极低、而[Ir(2-苯基吡啶)2(二吡啶-2-基甲醇)]+ 和[Ir(2-苯基吡啶)2(3-羟基-3,3-二(吡啶-2-基)丙腈)]+ 则是良好的光引发剂。DFT 和 TD-DFT 计算证实了参与吸收和发射过程的激发态具有 LC/MLCT 混合特性,并强调了辅助配体的两个亚基之间的 π 共轭在决定 LUMO 性质方面的作用。