Highly Regioselective Cyclodehydrogenation of Diphenylporphyrin on Metal Surfaces.

Zhang, Yong; Lu, Jianchen; Zhou, Hangjing; Zhang, Guang; Ruan, Zilin; Zhang, Yi; Zhang, Hui; Sun, Shijie et al. · ACS Nano · 2023

basic_science · Level V

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Abstract

Exploring the effect of porphin tautomerism on the regioselectivity of its derivatives is a big challenge, which is significant for the development and application of porphyrin drugs. In this work, we demonstrate the regioselectivity of 2<i>H</i>-diphenylporphyrin (H<sub>2</sub>-DPP) in the planarization reaction on Au(111) and Ag(111) substrates. H<sub>2</sub>-DPP monomer forms two configurations (<i>anti-</i> and <i>syn-</i>) via a dehydrogenation coupling, between which the yield of the <i>anti</i>-configuration exceeds 90%. Using high-resolution scanning tunneling microscopy, we visualize the reaction processes from the H<sub>2</sub>-DPP monomer to the final two planar products. Combined with DFT calculations of the potential reaction pathway and comparative experiments on Au(111) and Ag(111) substrates. Using M-DPP (M = Cu and Fe), we confirm that the regioselectivity of H<sub>2</sub>-DPP is derived from the reaction energy barrier during the cyclodehydrogenation reaction of different tautomers. This work reveals the regioselectivity mechanism of H<sub>2</sub>-DPP on the atomic scale, which holds great significance for understanding the chemical conversion process of organic macrocyclic molecules.