Guest‐Induced Photophysical Property Switching of Artificial Light‐Harvesting Dendrimers

An artificial light‐harvesting multiporphyrin dendrimer ( 8P Zn P FB ) composed of a focal freebase porphyrin ( P FB ) with eight zinc(II) porphyrin ( P Zn ) wings exhibited unique photophysical property switching in response to specific guest molecule binding. UV/Vis titration studies indicated stable 1:2 host–guest complex formation between 8P Zn P FB and meso ‐tetrakis(4‐pyridyl)‐porphyrin ( TPyP ) for which the first and second association constants were estimated to be >10 8 M −1 and 3.0×10 7 M −1 , respectively. 8P Zn P FB originally shows 94 % energy transfer efficiency from P Zn to the focal P FB . By the formation of the host–guest complex ( 8P Zn P FB ⋅ 2 TPyP ) the emission intensity of 8P Zn P FB is significantly decreased, and an ultrafast charge separation state is generated. The energy transfer process from P Zn wings to the P FB core in 8P Zn P FB is almost entirely switched to an electron transfer process by the formation of 8P Zn P FB ⋅ 2 TPyP .