Acta Chimica Sinica ›› 2023, Vol. 81 ›› Issue (12): 1716-1723.DOI: 10.6023/A23070349 Previous Articles     Next Articles



贾彦荣a, 徐凯a, 赵彦英a, 倪华钢a, 吴滢b, 夏敏a,*()   

  1. a 浙江理工大学 化学与化工学院 杭州 310018
    b 宁波市生态环境局 宁波 315000
  • 投稿日期:2023-07-20 发布日期:2023-10-31
  • 基金资助:
    国家自然科学基金(22273086); 金华市重大(重点)科学技术研究计划项目(2021-3-168)

Research on Emission Behavior and Mechanofluorochromic Activity of Benzo[d]imidazoles with Region-isomerized Push-Pull Groups

Yanrong Jiaa, Kai Xua, Yanying Zhaoa, Huagang Nia, Ying Wub, Min Xiaa()   

  1. a School of Chemistry and Chemical Engineering, Zhejiang Sci-Tech University, Hangzhou 310018
    b Ningbo Municipal Bureau of Ecology and Environment, Ningbo 315000
  • Received:2023-07-20 Published:2023-10-31
  • Contact: *E-mail:
  • Supported by:
    National Natural Science Foundation of China(22273086); Major (Key) Scientific and Technological Research Projects of Jinhua(2021-3-168)

Through the oxidation-cyclization of N-(4-cyanophenyl)-o-phenylenediamine and 1-pyrenylaldehyde or N-(1- pyrenyl)-o-phenylenediamine and 4-cyanobenzaldehyde in dimethyl sulfoxide under air, the two isomers BIMNPy and BIMCPy with pyrenyl and 4-cyanophenyl interchanged at N1 and C2 position on benzo[d]imidazole core were prepared while the photophysical properties of the double isomers in both solution and solid state were investigated. In solution, the emission of BIMCPy exhibited a moderate solvatochromic effect but the emission of BIMNPy was inert to the change of solvent polarity. The crystals of the two isomers displayed the blue-shifted mechanofluorochromic (MFC) behavior in response to force stimuli, but BIMNPy crystals possess the larger MFC activity. Moreover, the MFC on BIMNPy was reversible by fuming in solvent vapor or annealing and could be partly self-recovered at room temperature thanks to the less dense intermolecular interactions. However, the MFC on BIMCPy was irreversible under annealing and could only be recovered by fuming due to the indispensability of solvent molecules to form crystal lattices. In aid of differential scanning calorimetry, powder and single crystal X-ray diffraction, emission decay spectra as well as theoretical calculations, the reasons for the different emission behavior of the two isomers in solution and solid state were explored. It was revealed that the S2 excited state with both intramolecular charge transfer (ICT) and local emission (LE) features may account for the sensitive solvatochromism of BIMCPy, while the S2 excited state with only LE emission feature may be responsible for the inert solvatochromism of BIMNPy. Moreover, the different solid-state emission performance and MFC activity should be attributed to the particular molecular packing in crystals of the two isomers. Fundamentally, the varied dipole moments and the distinguishing π-conjugation extents induced by the region-isomerization of pyrenyl and 4-cyanophenyl with the push-pull electronic capability could be considered as the primary cause for the remarkably macroscopic differences of physical properties on the two isomers.

Key words: mechanofluorochromism, region-isomerization, benzo[d]imidazole, pyrenyl, molecular packing