Substituent-Dependent Photoexcitation Processes of π-Stacked Ion Pairs.

Porphyrin ion pairs, the charge of which is delocalized in core units, form tightly associated structures through i π- i π interactions. 5,10,15-Triphenyl-substituted porphyrin-Au III complex, which is favorable for forming stacked structures in the form of a stable ion, has been synthesized. Ion-pair metathesis based on the hard and soft acids and bases theory enabled combination with porphyrin anions possessing electronic states controlled by electron-donating and electron-withdrawing groups. Transient absorption spectroscopy suggested that the lifetimes of the radical pairs generated by photoinduced electron transfer of the ion pairs could be controlled by a judicious combination of the anions and cations.