Halogen atom effect of fluorinated tolanes on their luminescence characteristics
Halogen atom effect of fluorinated tolanes on their luminescence characteristics
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DOI：
10.1039/d1nj05539a
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发表时间：
2022-01-20
影响因子：
3.3
通讯作者：
Konno, Tsutomu
中科院分区：
文献类型：
--
作者：
Morita, Masato;Yamada, Shigeyuki;Konno, Tsutomu
卤素是元素周期表中第17族的化学元素，其电子构型为s(2)p(5)。在分子结构中加入卤素原子被认为是控制分子电子密度和分子聚集结构中分子排列的有力手段。因此，在分子结构中剪裁卤素原子是开发具有独特物理特性的功能分子的常用方法。本文研制了含氯（Cl）、溴（Br）和碘(i)等不同卤素原子的氟化甲苯，并对其光物理行为进行了详细评价。它们的光致发光（PL）行为在甲苯溶液中被发现是发射的，其发光效率（phi(PL)）高达0.60，而在室温下，简单的甲苯溶液通常显示出比这更低的发光。这些分子中PL效率的显著增强可能源于芳烃/氟芳烃相互作用，抑制了内部向暗激发态的转化。在结晶状态下，Cl取代的氟化甲苯显示出强烈的荧光，具有较高的phi(PL)，而用Br或I原子取代Cl显著降低了荧光，导致较低的phi(PL)；然而，在室温下，发现i取代氟化甲苯在晶体中表现出双重发射（荧光和磷光）。晶体结构分析表明，双发射可能是由于晶体中主要的分子间相互作用是氢和卤素键的结合。
Halogens are the chemical elements in group 17 of the periodic table, with an electronic configuration of s(2)p(5). Incorporation of the halogen atoms into molecular structures is well recognized as a powerful means to control the electron density of the molecule and molecular arrangement in molecular aggregate structures. Therefore, tailoring the halogen atoms in a molecular structure is a commonly used approach in the development of functional molecules with unique physical characteristics. Herein, fluorinated tolanes with various halogen atoms, for example, chlorine (Cl), bromine (Br), and iodine(i), were developed, and their photophysical behavior was evaluated in detail. Their photoluminescence (PL) behavior in toluene solution was found to be emissive, achieving a PL efficiency (phi(PL)) up to 0.60, while a simple tolane solution is generally reported to show lower emission than this at room temperature. The significant enhancement of PL efficiency in these molecules likely stems from the arene/fluoroarene interaction that suppresses internal conversion to dark excited states. In crystalline states, Cl-substituted fluorinated tolane showed intense fluorescence with high phi(PL), whereas replacing Cl with Br or I atoms notably reduced the fluorescence, resulting in low phi(PL); however, I-substituted fluorinated tolane was found to show dual emission (fluorescence and phosphorescence) in the crystal at room temperature. Crystal structural analyses revealed that the dual emission is likely attributable to the combination of hydrogen and halogen bonding interactions as key intermolecular interactions in the crystal.