A Hydrogen-Bonded Organic Framework Based on Pyrazinopyrazine
Qin Ji, Kiyonori Takahashi, Shin-ichiro Noro, Yusuke Ishigaki, Kenta Kokado, Takayoshi Nakamura,* Ichiro Hisaki*
ABSTRACT. Hydrogen-bonded organic frameworks (HOFs) composed of highly N-content π-conjugated molecules are expected to show multi-functionality. In this study, we studied on a HOF based on pyrazinopyrazine (PP), which is one of the most simple and essential structural motifs of highly N-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 H-bonded rhombic 2D network rapidly undergoes a guest release-induced three step structural transformation into other frameworks, including a semi-opening framework with small void, through rearrangement of H-bonds. These results provide insight to design new functional Nπ-HOFs and contribute to solid-state chemistry on porous molecular crystalline materials.