Synthesis and properties of porphyrin-expanded porphyrin click dyads

Six covalently linked 1,2,3-triazole bridged porphyrin-expanded porphyrin dyads containing Zn(II) porphyrin as energy donor and thiarubyrin, oxasmaragdyrin and BF2–oxasmaragdyrin as energy acceptors were synthesized under click reaction conditions. The click dyads were synthesized by coupling of azido Zn(II) porphyrin with ethynyl functionalized expanded porphyrins under Cu(I) catalyzed mild reaction conditions. Both rigid and flexible triazole bridges were used to understand the interaction between the Zn(II) porphyrin and expanded porphyrin units in dyads. The dyads were characterized by mass, NMR, absorption, fluorescence and electrochemical studies. The NMR, absorption and electrochemical studies indicated that the Zn(II) porphyrin and expanded porphyrin units in dyads interact weakly and maintain their independent characteristic features. The fluorescence studies indicated a possibility of energy transfer from donor Zn(II) porphyrin unit to expanded porphyrin unit such as oxasmaragdyrin and BF2–oxasmaragdyrin units in both flexible and rigid porphyrin-expanded porphyrin dyads.