On-surface synthesis of doubly-linked porphyrin polymers via cycloaromatization of isopropyl substituents on Au(111)
Abstract
We report the surface-mediated synthesis of doubly-linked porphyrin polymers (DPPs) on Au(111) via thermally induced polymerization of 5,10,15,20-tetrakis[4-(1-methylethyl)phenyl]-21H,23H-porphine. The transformation proceeds through a hierarchical process involving (i) [3 + 3] cycloaromatization of isopropyl substituents, (ii) intramolecular cyclodehydrogenation, and (iii) in situ metalation with Au atoms on Au(111). Combining scanning tunneling microscopy, scanning tunneling spectroscopy, and density functional theory calculations, we systematically elucidate the hierarchical transformation and electronic modulation of DPPs on Au(111). Charge density difference analysis reveals a significant electron transfer (∼1.04 e− per Au) from the Au atoms to the porphyrin π-system, accounting for the n-type doping effect and the transition from semiconducting to semimetallic behavior in the Au-metalated DPPs.

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