Generally, solvent incorporated-organic crystals easily undergo a structural collapse on removal of the solvent molecules. Very few examples retain their crystallinity during the process to exhibit permanent porosity1) or even show drastic structure change.2) They are expected to be a new type of crystalline host system.
Recently we reported high potential of 4-pyridyl-1,3-indanedione dimer (4PID) as a functional crystalline host material to give two specific packing structures, tightly packed "CLOSE" and solvent-included "OPEN" forms, selectively (Figure). The structural selectivity from "CLOSE" to "OPEN" crystal is easily switched by simple addition of a drop of various kinds of less-polar solvent in the crystallization condition. Interestingly, thermal removal of the solvent molecules from "OPEN" crystal affords a densely-packed "CLOSE" crystal via dynamic structure transformation without any crystallinity loss. Whereas, dipping "CLOSE" crystal in a specific solvent afforded again "OPEN" crystal without getting dissolved. Indanediones are known to show hemolysis/rejoin of the central C-C bond by outer stimuli. Further investigation applying such dynamic C-C bond together with the host-guest property of 4PID is highly attractive.
1) R. Cao et al., Angew. Chem., Int. Ed. 2016, 55, 9474.
2) H. Yamagishi et al., Science 2018, 361, 1242.
3) Y. Yakiyama et al., Chem.Commun. 2020, 56, 9687.
Yumi Yakiyama, Division of Applied Chemistry, Graduate School of Engineering, Osaka Universty