Azobenzene-Bridged Porphyrin Nanorings: Syntheses, Structures, and Photophysical Properties.
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.
Key Laboratory of Chemical Biology and Traditional Chinese, Medicine Research (Ministry of Education of China), Key Laboratory of Phytochemical R&D of Hunan Province, Key Laboratory of Application and Assembly of Organic, Functional Molecules, Hunan Normal University, Changsha 410081 (P.R. China).
Weiming
W
Huang
Spectroscopy Laboratory for Functional π-Electronic Systems, and Department of Chemistry, Yonsei University, Seoul 120-749 (Republic of Korea).
Seung-Kyu
SK
Lee
Spectroscopy Laboratory for Functional π-Electronic Systems, and Department of Chemistry, Yonsei University, Seoul 120-749 (Republic of Korea).
Young Mo
YM
Sung
Key Laboratory of Chemical Biology and Traditional Chinese, Medicine Research (Ministry of Education of China), Key Laboratory of Phytochemical R&D of Hunan Province, Key Laboratory of Application and Assembly of Organic, Functional Molecules, Hunan Normal University, Changsha 410081 (P.R. China).
Fulei
F
Peng
Key Laboratory of Chemical Biology and Traditional Chinese, Medicine Research (Ministry of Education of China), Key Laboratory of Phytochemical R&D of Hunan Province, Key Laboratory of Application and Assembly of Organic, Functional Molecules, Hunan Normal University, Changsha 410081 (P.R. China).
Bangshao
B
Yin
Key Laboratory of Chemical Biology and Traditional Chinese, Medicine Research (Ministry of Education of China), Key Laboratory of Phytochemical R&D of Hunan Province, Key Laboratory of Application and Assembly of Organic, Functional Molecules, Hunan Normal University, Changsha 410081 (P.R. China).
Ming
M
Ma
Key Laboratory of Chemical Biology and Traditional Chinese, Medicine Research (Ministry of Education of China), Key Laboratory of Phytochemical R&D of Hunan Province, Key Laboratory of Application and Assembly of Organic, Functional Molecules, Hunan Normal University, Changsha 410081 (P.R. China).
Bo
B
Chen
Key Laboratory of Chemical Biology and Traditional Chinese, Medicine Research (Ministry of Education of China), Key Laboratory of Phytochemical R&D of Hunan Province, Key Laboratory of Application and Assembly of Organic, Functional Molecules, Hunan Normal University, Changsha 410081 (P.R. China).|Research Computing Center, University of North Carolina, Chapel Hill, NC 27599-3420 (USA).
Shubin
S
Liu
Key Laboratory of Chemical Biology and Traditional Chinese, Medicine Research (Ministry of Education of China), Key Laboratory of Phytochemical R&D of Hunan Province, Key Laboratory of Application and Assembly of Organic, Functional Molecules, Hunan Normal University, Changsha 410081 (P.R. China).
Steven Robert
SR
Kirk
Spectroscopy Laboratory for Functional π-Electronic Systems, and Department of Chemistry, Yonsei University, Seoul 120-749 (Republic of Korea). dongho@yonsei.ac.kr.
Dongho
D
Kim
Key Laboratory of Chemical Biology and Traditional Chinese, Medicine Research (Ministry of Education of China), Key Laboratory of Phytochemical R&D of Hunan Province, Key Laboratory of Application and Assembly of Organic, Functional Molecules, Hunan Normal University, Changsha 410081 (P.R. China). jxsong@hunnu.edu.cn.
Jianxin
J
Song
azo compounds; cross-coupling; energy transfer; isomers; porphyrinoids