Wang Li, Liu Yan-Li, Li Quan-Jiang, Chen Sheng-Hui, He Di, Wang Mei-Shan
School of Physics and Optoelectronics Engineering, Ludong University, Yantai 264025, China.
School of Integrated Circuits, Ludong University, Yantai 264025, China.
J Phys Chem A. 2022 Feb 17;126(6):870-878. doi: 10.1021/acs.jpca.1c10236. Epub 2022 Feb 3.
π-conjugated aromatic diimides with chemical stability, heat resistance, and redox activity have attracted more attention due to their excellent fluorescence quantum yield in solution. The planar perylene diimide (PDI) derivatives generally have aggregation-induced emission quenching in the solid state, while the cyclic trimers based on pyromellitic diimides (PMDIs), naphthalene diimides (NDIs), and PDIs can increase the fluorescence quantum yield in the solid state and have large two-photon absorption cross section, which can be used as excellent nonlinear optical (NLO) materials. Therefore, this paper will study the effects of multiple assembly modes of the three monomers on the NLO responses of materials. It was found that the assembly modes of 2PMDI-1NDI and 2NDI-1PDI exhibit larger third-order NLO response (γ) values, which was due to the larger conjugate surface of PDI effectively reducing the energy gap between the HOMO and LUMO. Compared with other assembly methods, 2PMDI-1NDI and 2NDI-1PDI were conducive to causing redshifts (150 nm) in the absorption spectrum. Therefore, the larger conjugate surface of PDI and the assembly mode of the isosceles triangle were more favorable for intramolecular charge transfer, thus improving its NLO properties.
具有化学稳定性、耐热性和氧化还原活性的π共轭芳香二亚胺，因其在溶液中具有优异的荧光量子产率而备受关注。平面苝二亚胺（PDI）衍生物在固态下通常具有聚集诱导发光猝灭现象，而基于均苯四甲酸二亚胺（PMDI）、萘二亚胺（NDI）和PDI的环状三聚体在固态下可提高荧光量子产率，并具有较大的双光子吸收截面，可作为优异的非线性光学（NLO）材料。因此，本文将研究这三种单体的多种组装模式对材料NLO响应的影响。研究发现，2PMDI-1NDI和2NDI-1PDI的组装模式表现出更大的三阶NLO响应（γ）值，这是由于PDI较大的共轭表面有效降低了HOMO和LUMO之间的能隙。与其他组装方法相比，2PMDI-1NDI和2NDI-1PDI有利于使吸收光谱发生红移（150 nm）。因此，PDI较大的共轭表面和等腰三角形的组装模式更有利于分子内电荷转移，从而改善其NLO性能。
