One Pot Synthesis of Covalently Linked 14π Triphyrin–18π Porphyrin‐14π Triphyrin Triads

The first example of a covalently linked 14π triphyrin‐18π porphyrin‐14π triphyrin triad 4 , containing contracted triphyrin(2.1.1) and porphyrin/metalloporphyrin(1.1.1.1) subunits, was synthesized by condensation of β ‐dipyrromethanyl triphyrin(2.1.1) 2 with pentafluorobenzaldehyde in dry CH 2 Cl 2 using BF 3 ·OEt 2 as a Lewis acid catalyst under a nitrogen atmosphere for 45 min, followed by DDQ oxidation under open‐air conditions for an additional 30 min. Metallation of the porphyrin sub‐unit of free‐base triad 4 with Cu(CH 3 COO) 2 and Zn(CH 3 COO) 2 in a CHCl 3 /CH 3 OH afforded the corresponding triphyrin(2.1.1) 2 –metalloporphyrin triads 4‐Cu(II) and 4‐Zn(II) , respectively. The free‐base triad 4 and its metallated analogs 4‐Cu(II) and 4‐Zn(II) were thoroughly characterized by HR‐MS, 1D and 2D NMR spectroscopy, absorption spectroscopy, and DFT/TD‐DFT studies. These triads represent unique hybrid π‐conjugated macrocyclic systems comprising two distinct aromatic frameworks such as contracted 14π triphyrin(2.1.1) and regular 18π porphyrin(1.1.1.1), each exhibiting different electronic and structural characteristics. Electronic absorption and electrochemical studies revealed weak intramolecular interactions between the triphyrin and porphyrin subunits in triads 4 , 4‐Cu(II) , and 4‐Zn(II) . Furthermore, the DFT and TD‐DFT calculations were found to be consistent with the experimental observations.