Synthesis of Covalently Linked β‐ <i>Meso</i> ‐Phenyl Ethyne Bridged 14 <i>π</i> Triphyrin(2.1.1)–18 <i>π</i> Porphyrin(1.1.1.1) Dyads

The first examples of covalently linked, β-meso-phenyl ethyne bridged dyads 1-6 containing 14π triphyrin(2.1.1)/metallotriphyrin, and 18π porphyrin/metalloporphyrin subunits were synthesized in decent yields. The free base 14π triphyrin(2.1.1)-18π porphyrin(1.1.1.1) dyad 1 was prepared by Sonogashira cross coupling of β-monobromo triphyrin(2.1.1) 7 and 5-[4-ethynylphenyl]-10,15,20-tri(p-tolyl) porphyrin 8 in toluene/TEA at 40°C for 12 h. The triphyrin(2.1.1)-metalloporphyrin dyads 2, 3, and 4 were obtained by treating free base dyad 1 with NiCl₂, CuCl₂, and Zn(CH₃COO)₂ salts, respectively, in CHCl₃/CH₃OH at reflux, whereas metallotriphyrin-metalloporphyrin dyads 5 and 6 were synthesized by reacting dyads 2 and 4, respectively, with Re(CO)₅Cl in toluene/TEA under refluxing conditions. Dyads 1-6 are very unique and contain two different types of aromatic conjugated macrocycles, such as contracted 14π triphyrin(2.1.1) and regular 18π porphyrin(1.1.1.1), having different properties. The absorption and the electrochemical studies supported weak interactions between the subunits in dyads 1-6. The density functional theory (DFT) studies revealed that in dyads 1-6, the triphyrin(2.1.1)/metallotriphyrin and porphyrin/metalloporphyrin units were oriented with a dihedral angle in the range of 24°-65° with respect to each other.