Large Porphyrin Squares from the Self-Assembly of meso-Triazole-Appended L-Shaped meso-meso-Linked Zn super(II)-Triporphyrins: Synthesis and Efficient Energy Transfer

• Published in: Chemistry : a European journal Vol. 16; no. 17; pp. 5052 - 5061
• Main Authors: Maeda, Chihiro, Kim, Pyosang, Cho, Sung, Park, Jong Kang, Lim, Jong Min, Kim, Dongho, Vura-Weis, Josh, Wasielewski, MichaelR, Shinokubo, Hiroshi, Osuka, Atsuhiro
• Format: Journal Article
• Language: English
• Published: 01.05.2010
• Subjects: Arrays; Assembly; Cycloaddition; Excitation spectra; Porphyrins; Self assembly; Solvents; Spontaneous
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200903195

meso-Triazolyl-appended Zn super(II)-porphyrins were readily prepared by Cu super(I)-catalyzed 1,3-dipolar cycloaddition of benzyl azide to meso-ethynylated Zn super(II)-porphyrin (click chemistry). In noncoordinating CHCl sub(3) solvent, spontaneous assembly occurred to form tetrameric array (3) sub(2) from meso-meso-linked diporphyrins 3, and dodecameric porphyrin squares (4) sub(4) and (5) sub(4) from the L-shaped meso-meso-linked triporphyrins 4 and 5. The structures of these assemblies were examined by super(1)HNMR spectra, absorption spectra, and their gel permeation chromatography (GPC) retention time. Furthermore, the structures of the dodecameric porphyrin squares (4) sub(4) and (5) sub(4) were probed by small- and wide-angle X-ray scattering (SAXS/WAXS) measurements in solution using a synchrotron source. Excitation-energy migration processes in these assemblies were also investigated in detail by using both steady-state and time-resolved spectroscopic methods, which revealed efficient excited-energy transfer (EET) between the meso-meso-linked Zn super(II)-porphyrin units that occurred with time constants of 1.5ps super(-1) for (3) sub(2) and 8.8ps super(-1) for (5) sub(4). Getting it together: In a noncoordinating solvent, spontaneous assembly occurs to form a tetrameric array from meso-meso-linked diporphyrins, and a dodecameric porphyrin square from L-shaped meso-meso-linked triporphyrins (see graphic). Efficient excited-energy transfer (EET) between the meso-meso-linked Zn super(II)-porphyrin units was revealed.