Wang Hailan, Xiao Yuxin, Xie Zongliang, Sun Haodong, Zhang Xiayu, Wang Juan, Huang Rongjuan
Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE) and Shaanxi Institute of Biomedical Materials and Engineering (SIBME), Northwestern Polytechnical University (NPU), Xi'an, China.
School of Packaging and Materials Engineering, Hunan University of Technology, Zhuzhou, China.
Front Chem. 2021 Oct 19;9:766179. doi: 10.3389/fchem.2021.766179. eCollection 2021.
In this work, a new series of 2-hydroxybenzophenone (BPOH) derivatives, BPOH-TPA, BPOH-PhCz, and BPOH-SF substituting with different electron-donating groups are designed and synthesized. Dual-emission spectra are observed in solutions indicating their excited-state intramolecular proton transfer (ESIPT) character. In solid states, all compounds exhibit a broad emission spectrum when excited at low excitation energy, deriving from the enol-type form stabilized by intramolecular hydrogen bonds. Compound BPOH-TPA shows a clear excitation wavelength dependence. However, such behavior is absent in BPOH-PhCz and BPOH-SF, as the rigid and weaker donor moieties may restrict this process. Furthermore, by increasing the excitation energy, dual emission with a high-energy band ranging from 550 to 582 nm and a low-energy band ranging from 625 to 638 nm is obtained in all three molecules. The photophysical studies and single-crystal analyses are performed to further illustrate the excitation-dependent emission. Higher excitation energies can promote more excitons to keto forms via ESIPT, giving a stronger redshifted emission. BPOH-TPA with a stronger donor strength exhibits an obvious color change gradually from yellow to orange-red with the increasing excitation power from 1 to 15 mW/cm. This study provides a novel example of ESIPT materials with tunable emission colors.
在本工作中，设计并合成了一系列新的2-羟基二苯甲酮（BPOH）衍生物，即BPOH-TPA、BPOH-PhCz和BPOH-SF，它们带有不同的供电子基团。在溶液中观察到双发射光谱，表明其具有激发态分子内质子转移（ESIPT）特性。在固态下，所有化合物在低激发能量下激发时均表现出宽发射光谱，这源于通过分子内氢键稳定的烯醇型结构。化合物BPOH-TPA表现出明显的激发波长依赖性。然而，BPOH-PhCz和BPOH-SF中不存在这种行为，因为刚性且较弱的供体部分可能会限制这一过程。此外，通过增加激发能量，在所有三个分子中均获得了双发射，高能带范围为550至582 nm，低能带范围为625至638 nm。进行了光物理研究和单晶分析以进一步阐明激发依赖发射。更高的激发能量可以通过ESIPT促进更多激子转变为酮式结构，从而产生更强的红移发射。供体强度更强的BPOH-TPA随着激发功率从1 mW/cm增加到15 mW/cm，颜色逐渐从黄色明显变为橙红色。本研究提供了一个具有可调发射颜色的ESIPT材料的新实例。
