A new series of para-substituted 2,3-diphenyl-5-hydroxyquinoxaline ligands (LHn) were synthesised and characterised. These ligands were prepared in high yield via a two-step synthetic method. Four novel heteroleptic iridium(III) complexes were correspondingly prepared in high yield giving [Ir(ppy)2(Ln)]. Two X-ray crystallographic studies were undertaken on LH3 and [Ir(ppy)2(L2)] with each confirming the proposed formulations, with the complex showing the O,N-coordination mode of the quinoxalinato ligand. Density functional theoretical calculations were performed, firstly to compare the coordinated quinoxalinato system with the related quinolinato analogue, and secondly to probe the influence of the variation in para-substitution on the ancillary ligand. The calculations suggest that for either the quinoline or quinoxaline systems ligand-centred character appears to dominate the HOMO and LUMOs. Experimental electrochemical and spectroscopic characterisation showed that the subtle variations in absorption and emission wavelengths are probably due to ligand-dominated transitions that are influenced by the electronic nature of the para-substituted phenyl units in coordinated Ln.
我们合成了一系列新的对位取代的 2,3
-二苯基-5-羟基喹喔啉配体(LHn),并对其进行了表征。这些
配体是通过两步合成法以高产率制备的。相应地,还制备出了四种新型杂色
铱(III)配合物,并得到了高产率的[Ir(ppy)2(Ln)]。对 LH3 和[Ir(PY)2(
L2)]进行了两次 X 射线晶体学研究,结果均证实了所提出的配方,其中络合物显示了
喹喔啉配体的 O、N 配位模式。我们进行了密度泛函理论计算,首先是比较配位的
喹喔啉配位体系和相关的
喹啉配位类似物,其次是探究对位取代变化对辅助
配体的影响。计算结果表明,无论是
喹啉还是
喹喔啉系统,
配体中心特性似乎都主导着 HOMO 和 LUMO。实验电
化学和光谱特性分析表明,吸收和发射波长的微妙变化可能是由于
配体主导的转变,而
配体主导的转变受到配位 Ln 中对位取代的苯基单元的电子性质的影响。