Xiao Lu, Wu Yishi, Chen Jianwei, Yu Zhenyi, Liu Yanping, Yao Jiannian, Fu Hongbing
Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of chemistry, Chinese Academy of Sciences , Beijing 100190, People's Republic of China.
University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
J Phys Chem A. 2017 Nov 16;121(45):8652-8658. doi: 10.1021/acs.jpca.7b10160. Epub 2017 Nov 7.
The development of metal-free organic room temperature phosphorescence (RTP) materials has attracted increasing attention because of their applications in sensors, biolabeling (imaging) agents and anticounterfeiting technology, but remains extremely challenging owing to the restricted spin-flip intersystem crossing (ISC) followed by low-yield phosphorescence that cannot compete with nonradiative relaxation processes. Here, we report a facile strategy to realize highly efficient RTP by doping iodo difluoroboron dibenzoylmethane (I-BFdbm-R) derivatives into a rigid crystalline 4-iodobenzonitrile (Iph-C≡N) matrix. We found that halogen bonding between cyano group of Iph-C≡N matrix and iodine atom of I-BFdbm-R dopant is formed in doped crystals, i.e., Iph-C≡N···I-BFdbm-R, which not only suppresses nonradiative relaxation of triplets but also promotes the spin-orbit coupling (SOC). As a result, the doped crystals show intense RTP with an efficiency up to 62.3%. By varying the substituent group R in I-BFdbm-R from electron donating -OCH to electron accepting -F, -CN groups, the ratio between phosphorescence and fluorescence intensities has been systematically increased from 3.8, 15, to 50.
无金属有机室温磷光（RTP）材料的发展因其在传感器、生物标记（成像）剂和防伪技术中的应用而受到越来越多的关注，但由于自旋翻转系间窜越（ISC）受限，随后磷光产率低，无法与非辐射弛豫过程竞争，因此仍然极具挑战性。在此，我们报告了一种简便的策略，通过将碘代二氟硼二苯甲酰甲烷（I-BFdbm-R）衍生物掺杂到刚性晶体4-碘苯腈（Iph-C≡N）基质中来实现高效RTP。我们发现，在掺杂晶体中形成了Iph-C≡N基质的氰基与I-BFdbm-R掺杂剂的碘原子之间的卤键，即Iph-C≡N···I-BFdbm-R，这不仅抑制了三重态的非辐射弛豫，还促进了自旋轨道耦合（SOC）。结果，掺杂晶体显示出强烈的RTP，效率高达62.3%。通过将I-BFdbm-R中的取代基R从供电子的-OCH变为吸电子的-F、-CN基团，磷光与荧光强度之比已从3.8、15系统地增加到50。
