Substituent effect on the electroluminescence efficiency of amidinate-ligated bis(pyridylphenyl) iridium(III) complexes
Substituent effect on the electroluminescence efficiency of amidinate-ligated bis(pyridylphenyl) iridium(III) complexes
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DOI：
10.1039/c3tc32553a
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发表时间：
2014-06
影响因子：
6.4
通讯作者：
V. K. Rai;M. Nishiura;M. Takimoto;Z. Hou
中科院分区：
文献类型：
--
作者：
V. K. Rai;M. Nishiura;M. Takimoto;Z. Hou
本文报道了在脒基辅助配体的氮原子上具有不同取代基的杂配脒基/双(吡啶基苯基)铱(III)配合物的合成、结构以及光物理和电致磷光性质。双(吡啶基苯基)氯化铱(III)[(ppy)2Ir(μ-Cl)]2与各种脒基配体Li{(NR)(NR')CPh}的锂盐在80℃下反应，60-80%产生相应的杂配双(吡啶基苯基)/脒基铱(III)络合物，其通式如下[(ppy)2Ir{(NR)(NR′)CPh}]，其中 R = R′ = iPr (1)，R = R′ = t-Bu (2)，R = Et，R′ = t-Bu (3)，且 R = Et，R′ = (CH2)3N(CH3)2 (4)。这些杂配铱(III)配合物在室温下在甲苯溶液中表现出明亮的黄绿色磷光发射，具有中等光致发光(PL)量子产率(ΦPL = 0.16–0.34)和0.98–1.18 μs的短磷光寿命。有机发光二极管 (OLED) 是通过使用这些配合物作为磷光掺杂剂在 4,4'-N,N'-二咔唑联苯 (CBP) 主体中以不同浓度 (x = 5–100 wt%) 制造的。由于脒配体的空间位阻，在这些配合物中没有观察到显着的分子间相互作用，从而导致高电流/亮度下自猝灭和三重态湮灭的减少。观察到脒配体中的取代基对电致发光效率的显着影响。在这些配合物中，配合物（2）在脒基氮原子上含有庞大的叔丁基，表现出最高的电流效率（ηc：高达116 cd A−1）、功率效率（ηp：高达72.2 lm W−1）和外量子效率（ηext；高达16.3%）。
This paper reports the synthesis, structure, and photophysical and electrophosphorescence properties of heteroleptic amidinate/bis(pyridylphenyl) iridium(III) complexes having different substituents on the nitrogen atoms of the amidinate ancillary ligands. The reaction of bis(pyridylphenyl) iridium(III) chloride [(ppy)2Ir(μ-Cl)]2 with the lithium salt of various amidinate ligands Li{(NR)(NR′)CPh} at 80 °C gave in 60–80% yields the corresponding heteroleptic bis(pyridylphenyl)/amidinate iridium(III) complexes having a general formula [(ppy)2Ir{(NR)(NR′)CPh}], where R = R′ = iPr (1), R = R′ = t-Bu (2), R = Et, R′ = t-Bu (3), and R = Et, R′ = (CH2)3N(CH3)2 (4). These heteroleptic iridium(III) complexes exhibited bright yellowish-green phosphorescence emission with moderate photoluminescence (PL) quantum yields (ΦPL = 0.16–0.34) and short phosphorescence lifetimes of 0.98–1.18 μs in toluene solution at room temperature. Organic light-emitting diodes (OLEDs) were fabricated by the use of these complexes as phosphorescent dopants in various concentrations (x = 5–100 wt%) in the 4,4′-N,N′-dicarbazolylbiphenyl (CBP) host. Because of the steric hindrance of the amidinate ligands, no significant intermolecular interaction was observed in these complexes, thus leading to the reduction of self-quenching and triple–triplet annihilation at high currents/luminance. A significant influence of the substituents in the amidinate ligands on the electroluminescence efficiency was observed. Among these complexes, complex (2), which contains the bulky t-butyl group on the amidinate nitrogen atoms, showed the highest current efficiency (ηc: up to 116 cd A−1), power efficiency (ηp: up to 72.2 lm W−1) and external quantum efficiency (ηext; up to 16.3%).