A Hydrogen-Bonded Organic Framework Based on Pyrazinopyrazine

Hydrogen-bonded organic frameworks (HOFs) composed of high-nitrogen-content π-conjugated molecules are expected to show multifunctionality. In this study, we studied on a HOF based on pyrazinopyrazine (PP), which is one of the simplest and the most essential structural motifs of high-nitrogen-content polycyclic aromatic hydrocarbons. We describe synthesis of a PP-based building block molecule with four carboxyphenyl groups (CP-PP), spectroscopic and electronic properties of CP-PP and its ester precursor, structures of CP-PP-based HOFs, and thermal behaviors of the HOFs. Interestingly, the initial framework with hydrogen-bonded rhombic two-dimesnional (2D) network rapidly undergoes a guest release-induced three-step structural transformation into other frameworks, including a semiopening framework with small void, through rearrangement of hydrogen bonds. These results provide insight into design new functional Nπ-HOFs and contribute to solid-state chemistry on porous molecular crystalline materials.