Two- and three-dimensional β,β′-N-heterocycle fused porphyrins: concise construction, singlet oxygen production and electro-catalytic hydrogen evolution reaction

A powerful and concise synthesis of two- and three-dimensional β,β′-N-heterocycle fused porphyrins by palladium-catalyzed C–N coupling reaction of bromoporphyrins with arylamines has been demonstrated. Single crystal X-ray crystallographic analysis revealed that the quadruply N-heterocycle-fused porphyrins 7Ni and 8Ni possess a saddle-shaped structure and the porphyrin trimer 12Zn exhibits a three-bladed propeller conformation with a central triptycene uint. The maximal absorption of these porphyrins extends close to 900 nm. Electrochemical measurements and density functional theory (DFT) calculations were performed to gain insights into the electronic structure, spectral properties, and aromaticity of these heterocycle-fused porphyrins. The singlet oxygen (1O2) production and electrocatalytic hydrogen evolution reaction (HER) behaviours of these heterocycle-fused porphyrins were also investigated in this study.