Linear and star-shaped polynuclear Ru(ii) complexes of 2-(2′-pyridyl)benzimidazolyl derivatives: syntheses, photophysical properties and red light-emitting devices
作者:Wen-Li Jia、Yu-Feng Hu、Jun Gao、Suning Wang
DOI:10.1039/b515675k
日期:——
Two new star-shaped ligands with a 1,3,5-triphenylbenzene core, tmpb (1,3,5-tris[p-2-(2â²-pyridyl)benzimidazolylphenyl]benzene), and a 2,4,6-tris(p-biphenyl)-1,3,5-triazine core, tmbt (2,4,6-tris[p-2-(2â²-pyridyl)benzimidazolylbiphenyl]-1,3,5-triazine), have been synthesized. Their corresponding trinuclear Ru(II) complexes [Ru3(tmpb)(bpy)6](PF6)6 (3) and [Ru3(tmpt)(bpy)6](PF6)6 (4) have been obtained. Two dinuclear linear Ru(II) complexes with previously reported ligands bmb (1,4-bis[2-(2â²-pyridyl)benzimidazolyl]benzene) and bmbp (4,4â²-bis[2-(2â²-pyridyl)benzimidazolyl]biphenyl) and formulae [Ru2(bmb)(bpy)4](PF6)4 (1) and [Ru2(bmbp)(bpy)4](PF6)4 (2) have also been synthesized. Photophysical and electrochemical properties of the new compounds have been investigated. All four compounds display a characteristic metal-to-ligand-charge transfer (MLCT) absorption band and emit a red light when excited at the maximum of the MLCT band with emission maximum at 624, 629, 623 and 625 nm, respectively in neat films at ambient temperature. The emission quantum efficiency of the four complexes in neat films was determined to be 0.15, 0.17, 0.04 and 0.05, respectively. Light emitting devices based on these four compounds were fabricated by spin-casting the compound as a neat film to an ITO substrate, followed by the deposition of an aluminium metal layer. All devices emit a deep red light and the device behavior resembles that of a light emitting electrochemical cell. The EL maximum of the devices 1, 2, 3, and 4 is at 637, 657, 678, and 655 nm, respectively. All four devices have a fast response time when a sufficiently high voltage is applied. The device based on 2 is the brightest with a maximum luminance of 133 cd mâ2 at 7 V. The performance of devices based on 1, 2, and 4 is in general much more efficient than the device based on [Ru(bpy)3](PF6)2, which was fabricated and evaluated under the same experimental conditions as for the devices based on 1â4.
两种新的星形配体,一种是以 1,3,5-三苯基苯为核心的 tmpb(1,3,5-三[对-2-(2â²-吡啶基)苯并咪唑基苯基]苯),另一种是以 2、tmbt(2,4,6-三[对-2-(2â²-吡啶基)苯并咪唑基联苯]-1,3,5-三嗪)。得到了相应的三核 Ru(II) 复合物 [Ru3(tmpb)(bpy)6](PF6)6 (3) 和 [Ru3(tmpt)(bpy)6](PF6)6 (4)。以前报告过的配体 bmb(1,4-双[2-(2â²-吡啶基)苯并咪唑基]苯)和 bmbp(4、4â²-双[2-(2â²-吡啶基)苯并咪唑基]联苯)和 [Ru2(bmb)(bpy)4](PF6)4 (1) 和 [Ru2(bmbp)(bpy)4](PF6)4 (2) 的合成。对这些新化合物的光物理和电化学特性进行了研究。所有四种化合物都显示出特征性的金属-配体-电荷转移(MLCT)吸收带,并在 MLCT 带的最大值处激发时发出红光,在环境温度下,纯薄膜的发射最大值分别为 624、629、623 和 625 nm。经测定,这四种复合物在纯薄膜中的发射量子效率分别为 0.15、0.17、0.04 和 0.05。通过在 ITO 基底上旋铸化合物纯薄膜,然后沉积铝金属层,制造出了基于这四种化合物的发光器件。所有器件都能发出深红光,器件行为类似于发光电化学电池。器件 1、2、3 和 4 的 EL 最大值分别为 637、657、678 和 655 纳米。当施加足够高的电压时,这四个装置都具有快速的响应时间。基于 1、2 和 4 的器件的性能总体上比基于 [Ru(镱)3](PF6)2 的器件要高效得多,后者是在与基于 1â4 的器件相同的实验条件下制造和评估的。