A series of carbazole-based structural isomers appended with phenanthroimidazole and/or cyano chromophores are designed and synthesized. The structure–property relationship of bifunctionalized dyes is studied and compared with that of monofunctionalized dyes. The position of the chromophoric connectivity to the core carbazole is found to determine the physiochemical and electroluminescence properties of the isomeric dyes. The dyes with phenanthroimidazole incorporated at the C2 position of the carbazole offer a higher π-conjugation as compared to the dye with the C2 cyano-functionalized derivative. The incorporation of a phenylene spacer between the carbazole and phenanthroimidazole led to a red shift in emission, which is attributable to the reorganization of dye in the excited state. The C2 and C7 substituted bipolar dye offers more red-shifted emission because of the increased charge transfer component, which is further confirmed by its polar excited state in solvatochromism studies. The bifunctionalized dyes displayed high thermal/morphological stability with a thermal decomposition and glass transition temperature greater than 411 and 119 °C, respectively. Moreover, electrochemical measurements of the dyes reveal that the addition of a cyano substitution on the carbazole facilitates the stabilization of the LUMO. The materials are employed as dopant emitters in solution-processed multilayer organic light-emitting diode (OLED) devices and display deep-blue electroluminescence with Commission International L’Eclairage (CIE) coordinates of (0.16, 0.06) and external quantum efficiency of 5.7%, indicating the potential application for efficient blue OLEDs.

中文翻译：

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氰基对苯并咪唑取代咔唑衍生物功能特性的影响

设计并合成了一系列附加有菲咪唑和/或氰基发色团的咔唑基结构异构体。研究了双官能化染料的结构-性能关系，并与单官能化染料的结构-性能关系进行了比较。发现与核心咔唑的发色团连接的位置确定异构染料的物理化学和电致发光特性。与具有 C2 氰基官能化衍生物的染料相比，在咔唑的 C2 位置掺入菲咪唑的染料提供更高的 π 共轭。在咔唑和菲咪唑之间加入亚苯基间隔物导致发射红移，这归因于激发态染料的重组。由于增加了电荷转移成分，C2 和 C7 取代的双极性染料提供了更多的红移发射，这在溶剂致变色研究中通过其极性激发态得到进一步证实。双官能化染料显示出高热/形态稳定性，热分解温度和玻璃化转变温度分别大于 411 和 119 °C。此外，染料的电化学测量表明，在咔唑上添加氰基取代有利于 LUMO 的稳定化。该材料在溶液处理的多层有机发光二极管 (OLED) 器件中用作掺杂剂发射体，并显示深蓝色电致发光，国际照明委员会 (CIE) 坐标为 (0.16, 0.06)，外量子效率为 5.7% ,