Fine tuning of emission color of iridium(iii) complexes from yellow to red via substituent effect on 2-phenylbenzothiazole ligands: synthesis, photophysical, electrochemical and DFT study
作者:Ming Li、Hui Zeng、Yanyan Meng、Huiqin Sun、Song Liu、Zhiyun Lu、Yan Huang、Xuemei Pu
DOI:10.1039/c1dt10305a
日期:——
Four novel iridium(III) complexes bearing biphenyl (7a–7c) or fluorenyl (7d) modified benzothiazole cyclometallate ligands are synthesized. In comparison with the yellow parent complex, bis(2-phenylbenzothiozolato-N,C2′) iridium(III) (acetylacetonate) [(pbt)2Ir(acac)] (λPLmax = 557 nm, φPL = 0.26), 7a–7d show 20–43 nm bathochromic shifted orange or red phosphorescence in solution, with maximum photoluminescence (PL) quantum yield of 0.62, and PL lifetime of 1.8–2.0 μs. Meanwhile, the resulting complexes also exhibit intense orange or red phosphorescence of λPLmax = 588–611 nm in solid films. The complex 7c with two tert-butyl substituents possesses the highest phosphorescent efficiency both in dilute solution and thin solid films, therefore may be a prospective candidate for both doping and host emitting electrophosphorescent material. Furthermore, despite the observation of severe oxygen quenching for 7a–7d in solution, 7a and 7c even show efficient emission intensity quenching by oxygen in their solid state due to the existence of void channels in crystals; consequently, they are promising molecular oxygen sensor reagents. Electrochemical measurement and DFT calculation results suggest that all these chelates own declined LUMOs of 0.1 eV relative to that of (pbt)2Ir(acac) owing to the contribution of the phenyl substituents; whereas only 7d shows a more destabilized HOMO (∼0.1 eV) compared with the parent chelate.
合成了四种新型铱(III)配合物,分别带有改性的联苯(7a-7c)或芴基(7d)苯并噻唑环金属配体。与黄色母体配合物 bis(2-苯基苯并噻唑-N,C2')铱(III)(乙酰丙酮)[(pbt)2Ir(acac)](λPLmax=557 nm, φPL=0.26)相比,7a-7d在溶液中表现出橙色或红色磷光,最大发射波长红移20-43 nm,最大光致发光(PL)量子产率为0.62,PL寿命为1.8-2.0μs。同时,所得配合物在固态薄膜中也显示出强烈的橙色或红色磷光,最大发射波长为588-611 nm。具有两个叔丁基取代基的配合物7c在稀溶液和薄固态薄膜中都具有最高的磷光效率,因此可能是掺杂和主体发光电磷光材料的有前景的候选材料。此外,尽管在溶液中观察到7a-7d的严重氧猝灭,但7a和7c甚至在固态下由于晶体中存在空隙通道而表现出有效的氧猝灭发射强度;因此,它们是有前景的分子氧传感器试剂。电化学测量和DFT计算结果表明,由于苯基取代基的贡献,所有这些螯合物相对于(pbt)2Ir(acac)的LUMOs下降了0.1 eV;而只有7d的HOMO(约0.1 eV)比母体螯合物更不稳定。