Synthesis of Triazole‐Bridged Unsymmetrical Porphyrin Dyads and Porphyrin–Ferrocene Conjugates

A simple method has been used to synthesize four porphyrin azides with cores such as N 4 , N 3 S, N 2 SO and N 2 S 2 in 60–90 % yields by treating the corresponding aminoporphyrins with tert ‐butyl nitrite ( t BuONO) and azidotrimethylsilane (TMSN 3 ) in THF/CH 3 CN under mild reaction conditions. The hitherto unknown aminoporphyrins with heteroatom cores were synthesized from their corresponding nitroporphyrins by standard SnCl 2 /HCl reduction. The azidoporphyrins were used to synthesize six triazole‐bridged unsymmetrical porphyrin dyads containing two different types of porphyrin sub‐units as well as five triazole‐bridged porphyrin–ferrocene conjugates under Cu I ‐catalyzed “click” reaction conditions. Various Cu I ‐catalyzed reaction conditions were studied and the best yields of triazole‐bridged dyads and conjugates were obtained with CuI/DIPEA in THF/CH 3 CN at room temperature for overnight. The unsymmetrical porphyrin dyads and porphyrin–ferrocene conjugates were characterized by various spectroscopic and electrochemical techniques. In unsymmetrical porphyrin dyads, the NMR, absorption and electrochemical studies indicate a weak interaction between the two porphyrin sub‐units. However, preliminary photophysical studies support an efficient singlet‐singlet energy transfer from one porphyrin unit to another in five unsymmetrical dyads reported here. In porphyrin–ferrocene conjugates, the fluorescence of porphyrin was quenched significantly due to photo‐induced electron transfer from ferrocene to porphyrin.