First transition row metalloporphenes: metallic conductors or not?

Zinc porphene, a two-dimensional material made of fully fused zinc porphyrins and transferable to various substrates, has recently been synthesized on water surface and shown to be a semiconductor (10.26434/chemrxiv-2022-t84kd). This is in contrast with all previous calculations of its electronic structure, which predicted metallic conductivity. In this paper, we show how the Peierls distortion causes a gap-opening in zinc porphene and polymers with a square unit cell in general, thus giving an explanation of its electronic structure in agreement with experiment. Then, we explore the properties of first-row transition metalloporphenes, including some that carry a fifth or even a sixth ligand on the metal. Such highly tunable materials can be obtained by reversibly inserting different metal ions into the porphene macrocycles without removing any π centers from conjugation. We find that varying the metal produces both metallic conductors and semiconductors, with their electronic structure governed by the number of delocalized electrons and the extent of the Peierls distortion. The results suggest that it may be possible to advance flexible organic electronics by using lithography to pattern electronic circuitry in a monolayer or multilayer of metalloporphene, using it as a canvas for painting with a variety of metals and their ligands.