Assembled Structures and Cation-Anion Interactions in Crystals of Alkylimidazolium and Alkyltriazolium Iodides with Ferrocenyl Substituents

To investigate cation-anion interactions in imidazolium salts with ferrocenyl substituents, 1-ferrocenyl-3-alkyl-imidazolium iodides and their 1-ferrocenylphenyl derivatives were prepared and crystallographically characterized. In addition, triazole and pyrazole derivatives were also prepared. The triazole derivatives exhibited higher melting points than the corresponding imidazole derivatives. The iodide anions in the crystals are generally in contact with the azolium rings and are surrounded by azolium hydrogens of the neighboring cations via short CH center dot center dot center dot I contacts. These interactions between ionic moieties form two-dimensional networks leading to layer-like assembled structures. The imidazolium salts with ferrocenylphenyl substituents exhibited pi-pi interactions between the cations, whereas no such interactions were seen in other salts whose molecules are arranged orthogonal to each other. The crystal structures of ferrocenylimidazole and ferrocenylphenylimidazole were also determined and compared with those of other ferrocenylazoles.