Nanotechnologies / Materials
Functional organic materials, Porous materials

Development of co-crystalline organic materials
with arbitrary composition ratio
Department of Materials Engineering Science, Graduate School of Engineering Science
Professor Ichiro Hisaki						https://researchmap.jp/Ichiro_Hisaki?lang=en

Assistant Professor Ryusei Oketani		

https://researchmap.jp/ryuseioketani?lang=en

Nanotechnologies / Materials

Abstract
Porous crystalline materials constructed by mixing multiple components in indefinite ratios are attracting attention. Stepwise adjustment of functions by sweeping the mixing ratio is possible, andfurthermore, the emergence of new functions is expected. However, it is not easy to obtain the precise crystal structure informationnecessary to establish design guidance. In this study, crystalline
porous crystals with non-stoichiometric compositions were constructed by co-crystallization of two types of constituent molecules
in arbitrary proportions. The molecular arrangement in the crystals
was elucidated by single crystal X-ray structure analysis, and thecomposition ratio of both components was also determined. Furthermore, the distribution of each component in a single crystal
was clarified by micro-Raman spectroscopy using a single crystal.

▍ Background & Results
The advent of non-stoichiometric co-crystals, in which multiple
components are mixed in various proportions, has been recognized as an attractive system in materials science because of thepossibility of tuning functions by component ratios and, in somecases, the possibility of developing completely new functions.
Many non-stoichiometric co-crystals have been constructed byco-crystallization of compounds using charge-transfer interactions, halogen bonding, hydrogen bonding, and so on. However,
it is difficult to construct non-stoichiometric co-crystals of arbitrarycomposition using only organic molecules, as evidenced by thefact that the recrystallization operation eliminates a small amountof impurities and increases the purity of the compounds. We areparticularly interested in porous framework crystals. In the present
study, we have demonstrated proof-of-concept of an non-stoichiometric co-crystalline HOF with a well-defined crystalline structure
despite the mixture of components in various composition ratios,using tetracarboxylic acid derivatives with hexahydropyrene andpyrene skeletons, respectively. The molecular arrangement in thecrystals was elucidated by single crystal X-ray structural analysis,
and the composition ratio was determined. Furthermore, micro-Raman spectroscopy using single crystals has revealed the distribution of each component in a single crystal grain.

▍ Significance of the research and Future perspective
Crystalline structures created by mixing multiple components are
an important target for development in materials science because
they allow for fine tuning of functions depending on the mixing ratio
and have the potential to create functions that are not possible withstructures formed from single components. However, in general,
even when organic molecules are mixed, each component often
gives separate crystals. In this regard, we have obtained a guideline for constructing arbitrarily mixed single-crystalline organic materials by making good use of intermolecular interactions such ashydrogen bonding.
P a t e n t
Hashimoto, Taito; Oketani, Ryusei; Hisaki, Ichiro et al. Single crystalline, non-stoichiometric cocrystals of hydrogen-bonded organic frameworks. Angew.
Chem. Int. Ed. 2023, 62(1), e202215836. doi: 10.1002/anie.202215836
UR
L http://www.chem.es.osaka-u.ac.jp/mac/en/
K e y w o r d non-stoichiometric cocrystals, mixed crystal, porous materials
Tr e a t i s e