Feng Wan, Liu Ke, Zang Jianyang, Xu Jiale, Peng Haonan, Ding Liping, Liu Taihong, Fang Yu
Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China.
J Phys Chem B. 2021 Oct 21;125(41):11540-11547. doi: 10.1021/acs.jpcb.1c07296. Epub 2021 Oct 12.
Push-pull organic structures characterized by an intramolecular charge transfer (ICT) process and π-electron delocalization are potentially interesting luminescent materials. A series of three-dimensional -carborane-containing perylene bisimide derivatives (PBIs) were synthesized, and their optical properties were systematically investigated to illustrate the stereo effect, especially on the two-photon absorption (2PA) and optical power limiting (OPL) properties. Open-aperture Z-scan curves showed that all four PBIs displayed strong and broad two-photon absorptivities based on the resonance-enhanced phenomenon. The maximum degenerate two-photon absorption cross section (δ) increased with the number of PBI substituents. The derivative CB-PBI possessed a δ value of ∼2400 GM at 650 nm, a significant enhancement in comparison with that of the parent PBI (∼719 GM), ascribed to the present stereo effect. When the aromatic-donating units changed from naphthyl and pyrenyl to PBI, the generated multidimensional intramolecular charge transfer (ICT) from the aromatic units to the -carborane cage contributed to the 2PA processes. All of the fluorophores exhibited excellent optical power limiting (OPL) performances as well as a minimum limiting threshold of ∼4.98 mJ/cm for CB-PBI. These significant results not only allow us to get deep insight into the nature of the fundamental stereo effect and nonlinear optical (NLO) response involved but also guide us toward the design of new multifunctional luminescent materials.
以分子内电荷转移（ICT）过程和π电子离域为特征的推挽有机结构是潜在有趣的发光材料。合成了一系列含三维碳硼烷的苝二酰亚胺衍生物（PBIs），并系统研究了它们的光学性质，以阐明立体效应，特别是对双光子吸收（2PA）和光限幅（OPL）性质的影响。开孔Z扫描曲线表明，基于共振增强现象，所有四种PBIs都表现出强而宽的双光子吸收能力。最大简并双光子吸收截面（δ）随PBI取代基数量的增加而增大。衍生物CB-PBI在650 nm处的δ值约为2400 GM，与母体PBI（约719 GM）相比有显著增强，这归因于当前的立体效应。当芳香供体单元从萘基和芘基变为PBI时，从芳香单元到碳硼烷笼产生的多维分子内电荷转移（ICT）有助于2PA过程。所有荧光团都表现出优异的光限幅（OPL）性能，CB-PBI的最小限幅阈值约为4.98 mJ/cm²。这些重要结果不仅使我们能够深入了解所涉及的基本立体效应和非线性光学（NLO）响应的本质，而且还指导我们设计新型多功能发光材料。
