Sterically crowded hydrogen-bonded hexagonal network frameworks

Abstract

A hydrogen-bonded hexagonal network (H-HexNet) composed of C₃-symmetric π-conjugated molecules with six carboxyphenyl groups is one of the candidate platforms for porous organic materials. For formation of H-HexNets, a triangular cyclic structure, a so-called phenylene triangle (PhT) motif, composed of hydrogen bonded carboxyphenyl groups is a key structure. In this paper, we synthesized two derivatives of hexakis(carboxyphenyl)triphenylene TpMe and TpF, in which substituents (Me or F) were introduced in the ortho-positions of the carboxy groups, to investigate whether the PhT motif forms and how the structure and property of H-HexNets are affected by steric bulkiness around the hydrogen bonding moieties. Crystal structures, thermal stability, evaluation of permanent porosity by gas sorption experiments, and photochemical properties are revealed, which can contribute to establishment and fine-tuning of porous organic materials based on H-HexNets.