Design and synthesis of Bipyridine Platinum(II) Bisalkynyl Fullerene Donor-Chromophore-Acceptor triads with ultrafast charge separation

摘要

Donor chromophore acceptor triads, (PTZ)(2)-Pt(bpy)C-60 and ((1)BuPTZ)(2)-Pt(bpy)-C-60, along with their model compound, (Ph)(2)-Pt(bpy)-C-60, have been synthesized and characterized; their photophysical and electrochemical properties have been studied, and the origin of the absorption and emission properties has been supported by computational studies. The photoinduced electron transfer reactions have been investigated using the femtosecond and nanosecond transient absorption spectroscopy. In dichloromethane, (Ph)(2)-Pt(bpy)-C-60 shows ultrafast triplet triplet energy transfer from the 3MLCT/LLCT excited state within 4 ps to give the 3C60* state, while in (PTZ)(2)Pt(bpy)-C-60 and ((1)BuPTZ)(2)-Pt(bpy)-C-60, charge-separated state forms within 400 fs from the 3MLCT/LLCT excited state with efficiency of over 0.90, and the total efficiency with the contribution of C-3(60)* is estimated to be 0.99. Although the forward electron transfer reactions are very rapid, the charge-separated state recombines to the singlet ground state at a time of hundreds of nanoseconds because of the difference in spin multiplicity between the charge-separated state and the ground state.