Systematic Electronic Control in Ambipolar Compounds Optimizes Their Photoluminescence Properties: Synthesis, Characterization, and Device Fabrication of Four‐Coordinate Boron Compounds Containing an N,O‐Chelating Oxazolylphenolate Ligand
Systematic Electronic Control in Ambipolar Compounds Optimizes Their Photoluminescence Properties: Synthesis, Characterization, and Device Fabrication of Four‐Coordinate Boron Compounds Containing an N,O‐Chelating Oxazolylphenolate Ligand
复制标题
DOI：
10.1002/ejic.200900017
复制
发表时间：
2009-04
影响因子：
2.3
通讯作者：
Ho‐Jin Son;Won‐Sik Han;Kyung‐Ryang Wee;Ji-Yun Chun;K. Choi;S. Han;Soonnam Kwon;J. Ko;Chongmok Lee;S. Kang
中科院分区：
文献类型：
--
作者：
Ho‐Jin Son;Won‐Sik Han;Kyung‐Ryang Wee;Ji-Yun Chun;K. Choi;S. Han;Soonnam Kwon;J. Ko;Chongmok Lee;S. Kang
通过用2-(4,4-二甲基-4,5-二氢恶唑-2-基)-4-X-芳基酚(HOPhOxZArX; 4a-f)或三苯基硼(TPB)处理，制备了一系列N,O-(OPhOxZArX)BPh2或N,O-(OPhOxZNPh2)BPh2 (5a-g)类型的四配位硼化合物。 2-(4,4-二甲基-4,5-二氢恶唑-2-基)-4-(4-二苯基氨基)苯酚(HOPhOxZNPh2；4g)。通过在酚盐的 4 位结合吸电子 (EW) 和供电子 (ED) 基团 [ArX (X = 4-氰基-、2,4-二氟-、4-氯-、苯基、4-甲氧基-和 4-二甲氨基苯基) 或 NPh2]，这些化合物的电子结构发生系统变化。与 EW 组中观察到的相比，ED 组的吸收和发射最大值显示出显着的红移。这种红移表明，一旦硼中心插入相应的配体中，π-共轭就会有效地延伸到芳基酚盐和恶唑啉部分上。发现从 EW 组到 ED 组观察到的带隙逐渐减小与循环伏安 (CV) 实验确定的氧化电位的增加一致。特别是，EW 和 ED 取代基与氧化电位之间的哈米特图证实了基态电子扰动。这种变化主要归因于 HOMO 能级的升高，对每个系统前沿轨道的一系列理论计算进一步证实了这一点。 ED基团(-NPh2)取代的化合物5g由于络合物中的分子内电荷转移而显示出双极性特征，在甲苯中获得最高的光致发光量子产率。这种新型硼络合物被发现可用作电致发光 (EL) 器件中的发射极，在 13 V 电压下的最大亮度为 2905 cd/m2，在 6 mA/cm2 电流下的电流效率为 1.63 cd/A，开启电压为 4.3 V。（© Wiley-VCH Verlag GmbH & Co. KGaA，69451 Weinheim，德国，2009 年）
A series of four-coordinate boron compounds of the type N,O-(OPhOxZArX)BPh2 or N,O-(OPhOxZNPh2)BPh2 (5a–g) has been prepared by treating triphenylboron (TPB) with2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)-4-X-arylphenols(HOPhOxZArX; 4a–f) or 2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)-4-(4-diphenylamino)phenol (HOPhOxZNPh2; 4g). A systematic change in the electronic structures is achieved in these compounds by incorporating electron-withdrawing (EW) and -donating (ED) groups [ArX (X = 4-cyano-, 2,4-difluoro-, 4-chloro-, phenyl, 4-methoxy-, and 4-dimethylaminophenyl) or NPh2] at the 4-position of the phenoxide. The absorption and emission maxima of the ED groups show a significant red-shift compared to those observed in the EW groups. This red-shift suggests that π-conjugation is effectively extended over the arylphenoxides and oxazoline moiety once the boron center has been plugged into the corresponding ligands. The gradual decrease observed in the bandgaps on going from EW to ED groups is found to be in agreement with the increase in oxidation potentials determined by the cyclic voltammetry (CV) experiments. In particular, a Hammet plot between the EW and ED substituents and oxidation potentials confirms the ground state electronic perturbation. Such alterations are attributed mainly to an elevation of the energy levels of the HOMOs), as further confirmed by a series of theoretical calculations on the frontier orbitals of each system. The ED group (-NPh2) substituted compound 5g shows a bipolar character due to intramolecular charge transfer in the complex, with the highest photoluminescence quantum yield being obtained in toluene. This new boron complex was found to function as an emitter in electroluminescence (EL) devices, with a maximum brightness of 2905 cd/m2 at 13 V and a current efficiency of 1.63 cd/A at 6 mA/cm2, with a turn-on voltage of 4.3 V.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)