Cocrystals with three π-components, which were a π-cation, a π-anion acting as a hydrogen-bond acceptor, and a π-molecule acting as a hydrogen-bond donor, were prepared by the solution-growth methods. The first and second components were ion pairs of 1-methylpyridinium or 1-methylquinolinium p-toluenesulfonate derivatives, and the third components were dihydric phenol derivatives, like hydroquinone, 1,4-naphthalenediol, 4,4’-biphenol, and 1,1’-bi-2-naphthol, or benzoic acid derivatives with hydroxy or amino group at the para position. Among 23 cocrystals found from 35 possible combinations of five ion-pairs and seven hydrogen-bond donors, 20 cocrystals were investigated by the X-ray crystallographic analyses. Some of them also contained solvent molecules. In these cocrystals, hydrogen-bond sequences composed of p-toluenesulfonate and the hydrogen-bond donors were observed, and ionic bonds between the first and second components and hydrogen bonds between the second and third components were found to be responsible for three-π-component cocrystals. When the cations were 4-cyanopyridinium or quinolinium derivatives, the cocrystals showed charge-transfer absorption bands due to electronic interaction between the cations and the hydrogen-bond donors. To the mixture of quinolinium p-toluenesulfonate and 1,1’-bi-2-naphthol forming the three-π-component cocrystals, tetrathiafulvalene were added to form four-π-component cocrystals with ethanol or water molecules.
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