Azobenzene-Bridged Porphyrin Nanorings: Syntheses, Structures, and Photophysical Properties

Weiming Huang, Seung Kyu Lee, Young Mo Sung, Fulei Peng, Bangshao Yin, Ming Ma, Bo Chen, Shubin Liu, Steven Robert Kirk, Dongho Kim, Jianxin Song

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10 Citations (Scopus)

Abstract

Azobenzene-bridged β-to-β and meso-to-meso porphyrin nanorings were successfully synthesized by a palladium-catalyzed Suzuki-Miyaura coupling reaction in a logical synthesis. The dimeric structure was confirmed by XRD analysis. The azo linkages in di- and tetramers are in the all-trans conformation, whereas in the trimers one azo linkage can be interconverted between cis and trans under external stimulation. When trimeric isomers are heated to 333 K or higher, the azo linkages will be in the all-trans configurations: the pure all-trans trimer can be kept in the dark for several months. Fluorescence anisotropy and pump-power-dependent decay results revealed excitation energy transfer for azobenzene-bridged zinc-porphyrin nanorings. The distances between porphyrin units of these azobenzene-bridged porphyrin arrays are almost the same, but the exciton energy hopping (EEH) times for each wheel are markedly different. The dimer and meso-to-meso tetramer possess relatively short excitation energy transfer (EET) times (1.28 and 2.48 ps, respectively) due to their good planarity and rigidity. In contrast, the EET time for the trimeric zinc(II)-porphyrin array (6.9 ps) is relatively long due to its nonradiative decay pathway (i.e., cis/trans isomerization of azobenzene). Both di- and tetramers exhibit relatively high fluorescence quantum yields, whereas the trimers show weak emission because of structural differences. Interconversion versus ring strain: Azobenzene-bridged zinc-porphyrin (ZnP) nanorings were successfully synthesized through Suzuki-Miyaura reactions. Trimers show trans-cis isomerization due to molecular flexibility (see figure), whereas di- and tetramers are locked by the geometries of the cyclic structures.

Original languageEnglish
Pages (from-to)15328-15338
Number of pages11
JournalChemistry - A European Journal
Volume21
Issue number43
DOIs
Publication statusPublished - 2015 Oct 1

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Organic Chemistry

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    Huang, W., Lee, S. K., Sung, Y. M., Peng, F., Yin, B., Ma, M., Chen, B., Liu, S., Kirk, S. R., Kim, D., & Song, J. (2015). Azobenzene-Bridged Porphyrin Nanorings: Syntheses, Structures, and Photophysical Properties. Chemistry - A European Journal, 21(43), 15328-15338. https://doi.org/10.1002/chem.201502296