Imaging Science and Photochemistry ›› 2017, Vol. 35 ›› Issue (5): 686-697.DOI: 10.7517/j.issn.1674-0475.2017.04.029

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Photoinduced Decarboxylation Reaction in New Cd-benzothiadiazole Metal-organic Framework

CHENG Qing, YU Feihu, HAN Xiao, MA Ke, DING Jie, HOU Hongwei   

  1. College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, Henan, P. R. China
  • Received:2017-05-03 Revised:2017-05-26 Online:2017-09-15 Published:2017-09-15

Abstract:

Based on the same benzothiadiazole (BTD) ligand (H2L=2,1,3-benzothiadiazole-4,7-dicarboxylic acid), two new 3D BTD-derived Cd(Ⅱ) metal-organic frameworks 1[Cd4(BTDC)4·5H2O] and 2[Cd2(BTDC)2(DMF)·1.5H2O] were obtained by the different solvothermal reactions. Interestingly, in 1, partial BTD units arranged in an anti-parallel mode, and the distance between these BTD units was 3.987 Å, which was less than that valued by theoretical calculation (4 Å). Furthermore, evidencedby UV-Vis solid state absorption spectra of 1, the energy of absorption band at 470 nm was lower than those from typical monomer-BTD unit. Hence, the structural analysis and photophysical study distinctly demonstrated the evidence of BTD anti-dimmerin 1. More importantly, the UV and fluorescence spectra after illumination showed that there were interesting photochromic phenomena in both complexes 1 and 2 triggered by photoinduced electron transfer, where anionic radical was also directly observed by the electron paramagnetic resonance (EPR) spectra before and after the illumination. Herein, FT-IR spectra show that the subsequent decarboxylation of ligand unit results to release CO2 gas (2331 cm-1, 2361 cm-1) in complexes 1 and 2.

Key words: Benzothiadiazole-MOFs, photo-induced decarboxylation, anionic radical