Infinite Stacking of Antiaromatic Ni(II) Norcorroles Formed in a Porous Hydrogen-Bonded Organic Framework

Antiaromatic molecules are known for their intriguing physical properties and high reactivity, which arise from their unique electronic structures. While the properties of individual antiaromatic molecules have been extensively studied, research on their assembled structures is still in the early stages. In this work, we synthesized a hydrogen-bonded organic framework, named Nor-HOF, using a stable antiaromatic molecule, Ni(II) norcorrole, as a building block. Single-crystal X-ray structure analysis revealed that Nor-HOF possesses a one-dimensional columnar structure of infinitely stacked Ni(II) norcorroles with permanent porosity. Theoretical calculations indicated that the norcorroles in Nor-HOF interact through their molecular orbitals while retaining their antiaromaticity. Furthermore, we demonstrated that the oxidation of the norcorrole columns by adsorption of I₂ into the pores enhances the electrical conductivity of Nor-HOF by approximately 1000-fold. This work opens a new perspective on exploiting the periodic structure of antiaromatic molecules for the development of advanced functional materials.