Kim Namkyun, You Dong Kyun, Kim Soyeon, Kim Dongwook, Cho Kanghee, Lee Kang Mun
Department of Chemistry, Institute for Molecular Science and Fusion Technology, Kangwon National University, Chuncheon, Gangwon 24341, Republic of Korea.
Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Republic of Korea.
Inorg Chem. 2024 Aug 12;63(32):15044-15052. doi: 10.1021/acs.inorgchem.4c01875. Epub 2024 Jul 29.
Two -carboranes with (i) 9,9-dimethyl-9-xanthene and (ii) spiro[fluorene-9,9'-xanthene] moieties ( and , respectively) were prepared and characterized. Single X-ray crystallography analysis revealed the presence of intermolecular hydrogen bonds in crystals. Although both compounds did not exhibit emission in tetrahydrofuran solutions at 298 K, intense bluish emission was observed in the solid states and frozen tetrahydrofuran solutions at 77 K. According to the results of theoretical calculations, this emission originated from an intramolecular charge transfer (ICT) transition with the -carborane moiety. The absolute quantum efficiency (Φ) of the ICT-based emission in the film state equaled 49% for and 20% for but was as high as 90% for the crystals of both compounds. The crystal structures of and revealed that the -carboranyl-appended phenyl plane was orthogonal (85-89°) to the carbon-carbon bonding axis in the -carborane, indicating the existence of a strong -π-interaction, which was identified as the structural basis for the ICT-based transition. These results implied that the intermolecular structural effect of in the randomly aggregated solid state (film) helped maintain the above orthogonality and, hence, the high efficiency from the ICT radiative mechanism. Thus, we concluded that the ICT radiative efficiency of -carboranyl luminophores in the aggregated solid state can be controlled by specific intermolecular interactions and that the molecular geometric design inducing this feature can be important for developing highly efficient carboranyl luminophores.
制备并表征了带有（i）9,9-二甲基-9-占吨基和（ii）螺[芴-9,9'-占吨]部分（分别为 和 ）的双碳硼烷。单晶X射线晶体学分析表明在 晶体中存在分子间氢键。尽管这两种化合物在298K的四氢呋喃溶液中均未表现出发光现象，但在77K的固态和冷冻四氢呋喃溶液中观察到强烈的蓝色发光。根据理论计算结果，这种发光源于与碳硼烷部分的分子内电荷转移（ICT）跃迁。对于 ，基于ICT的发光在薄膜状态下的绝对量子效率（Φ）为49%，对于 为20%，但对于这两种化合物的晶体，该效率高达90%。 和 的晶体结构表明，连接碳硼烷基的苯基平面与碳硼烷中的碳-碳键轴正交（85-89°），这表明存在强 -π相互作用，该相互作用被确定为基于ICT跃迁的结构基础。这些结果表明， 在随机聚集的固态（薄膜）中的分子间结构效应有助于维持上述正交性，从而有助于基于ICT辐射机制的高效率。因此，我们得出结论，聚集固态中碳硼烷基发光体的ICT辐射效率可通过特定的分子间相互作用来控制，并且诱导这种特性的分子几何设计对于开发高效碳硼烷基发光体可能很重要。
