Structural Extension from an Isonicotinic Acid Dimer to 4-(4-Pyridyl)benzoic Acid (pybenH) Dimer: X-ray Crystal Structure Analysis and Inclusion Properties of a Hydrogen-Bonded Coordination Polymer [Ni(SCN)2(pybenH)2]∞

This study reports the X-ray crystal structure analysis and inclusion properties of a hydrogen-bonded coordination polymer [Ni(SCN)2(pybenH)2]∞. The crystal structures of inclusion compounds (1–18) are best described as compounds consisting of layers. The inclusion compounds are classified into two categories: compounds with channels (channel types A (1–15) and B (16 and 17)) and compounds with isolated cavities (type I (18)). Except 18, the crystal structures are similar to each other despite different molecular structures of the guests. X-ray diffraction analysis has elucidated that the interlayer separation, the position of the cavity, and the cavity volume are adjusted to the guests. In addition, the large cavity enables the guests to adjust their positions and orientations in the channels. These backgrounds cancel out the different steric requirements of the guests to a certain extent, and, as a result, the crystal structures are similar to each other. The exceptional case of 18 is due to the molecular structure and volume of pyrene being suitable to occupy the isolated cavities formed in type I.