We have prepared supramolecular assemblies of hexaaryl-anchored polyester zinc(II) porphyrin dendrimers (6PWZn, 12PZnW, and 24P ZnW) with various bipyridyl guests (CnPy2; n = 1, 2, 4, 6, and 8) through self-assembled coordination to control the structures and photophysical properties. We comparatively investigated the photophysical properties of porphyrin dendrimers with and without guest binding by using ensemble and single-molecule spectroscopy. The spectrophotometric titration data of dendrimers with guest molecules provide a strong indication of the selective intercalation of bipyridyl guests into porphyrin dendrimers. The representative dendrimer assembly 12PZnW⊃C6Py2 exhibits increased fluorescence quantum yield and lifetime in ensemble measurements, as well as higher initial photon count rates with stepwise photobleaching behavior in the single-molecule fluorescence intensity trajectories (FITs) compared to 12PZnW. At the single-molecule level, the higher photostability of 12PZnW⊃C6Py2 can be deduced from the long durations of the first emissive levels in the FITs. We attribute the change in photophysical properties of the dendrimer assemblies to their structural changes upon intercalation of guest molecules between porphyrin units. These results provide new insight into the control of porphyrin dendritic structures using appropriate bidentate guests in poor environmental conditions.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry