Department of Chemistry Education, Kongju National University, 56 Gongjudaehak-ro, Gongju 32588, Republic of Korea.
Int J Mol Sci. 2023 Feb 24;24(5):4504. doi: 10.3390/ijms24054504.
The development of pyrene-based fluorescent assembled systems with desirable emission characteristics by reducing conventional concentration quenching and/or aggregation-induced quenching (ACQ) is highly desirable. In this investigation, we designed a new azobenzene-functionalized pyrene derivative (AzPy) in which sterically bulky azobenzene is linked to pyrene. Absorption and fluorescence spectroscopic results before and after molecular assembly indicate that even in a dilute N,N-dimethylformamide (DMF) solution (~10 μM), AzPy molecules experienced significant concentration quenching, whereas the emission intensities of AzPy DMF-HO turbid suspensions containing self-assembled aggregates were slightly enhanced and showed similar values regardless of the concentration. The shape and size of sheet-like structures, from incomplete flakes less than one micrometer in size to well-completed rectangular microstructures, could be adjusted by changing the concentration. Importantly, such sheet-like structures exhibit concentration dependence of their emission wavelength from blue to yellow-orange. Comparison with the precursor (PyOH) demonstrates that the introduction of a sterically twisted azobenzene moiety plays an important role in converting the spatial molecular arrangements from H- to J-type aggregation mode. Thus, AzPy chromophores grow into anisotropic microstructures through inclined J-type aggregation and high crystallinity, which are responsible for their unexpected emission characteristics. Our findings provide useful insight into the rational design of fluorescent assembled systems.
发展具有理想发射特性的基于芘的荧光组装体系，以降低传统的浓度猝灭和/或聚集诱导猝灭（ACQ），这是非常可取的。在这项研究中，我们设计了一种新的偶氮苯功能化芘衍生物（AzPy），其中空间位阻较大的偶氮苯与芘相连。分子组装前后的吸收和荧光光谱结果表明，即使在稀有的 N,N-二甲基甲酰胺（DMF）溶液（~10 μM）中，AzPy 分子也经历了显著的浓度猝灭，而含有自组装聚集体的 AzPy DMF-HO 浊液的发射强度略有增强，并且无论浓度如何，其值都相似。片状结构的形状和尺寸，从小于一微米的不完整薄片到完整的矩形微结构，可以通过改变浓度来调节。重要的是，这种片状结构表现出其发射波长从蓝色到黄橙色的浓度依赖性。与前体（PyOH）的比较表明，引入空间扭曲的偶氮苯部分在将空间分子排列从 H 型转换为 J 型聚集模式方面起着重要作用。因此，AzPy 生色团通过倾斜的 J 型聚集和高结晶度生长成各向异性的微结构，这是它们产生意外发射特性的原因。我们的发现为荧光组装体系的合理设计提供了有用的见解。
