Large porphyrin squares from the self-assembly of meso-Triazole-Appended L-Shaped meso-meso-Linked Zn~(II)-Triporphyrins: synthesis and efficient energy transfer

摘要

meso-Triazolyl-appended Zn~(II)porphyrins were readily prepared by Cu~I-catalyzed 1, 3-dipolar cycloaddi-tion of benzyl azide to meso-ethynylat-ed Zn~(II)-porphyrin (click chemistry). In noncoordinating CHCl_3 solvent, spon-taneous assembly occurred to form tet-rameric array (3)_2: from meso-meso-linked diporphyrins 3 _1 and dodecameric porphyrin squares (4)_4 and (5) _4 from the L-shaped meso-meso-linked tripor-phyrins 4 and 5. The structures of these assemblies were examined by ~1H NMR spectra, absorption spectra, and their gel permeation chromatography (GPC) retention time. Furthermore, the struc-tures of the dodecameric porphyrin squares (4) _4 and (5)_4 were probed by small- and wide-angle X-ray scattering (SAXS/WAXS) measurements in solu-tion using a synchrotron source. Excita-tion-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~(II)-porphyrin units that occurred with time constants of 1.5 ps~(-1) for(3)_2 and 8.8ps~(-1) for (5)_4.