1,3-Dibenzylimidazolium salts: A paradigm of water and anion effect on the supramolecular H-bonds network

Two crystals of 1.3-dibenzylimidazolium salts with chloride (crystal I) and hexafluorophosphate (crystal III) have been obtained by slow evaporation or a saturated aqueous solution for I and saturated chloroform solution for Ill. The two structures are described and compared to the corresponding bromide salt (crystal II). The X-ray diffraction studies on single crystals revealed that the three crystalline materials are monoclinic with P2(1)/n or P2(1)/c space group. The structures of I and III are completely different compared to that of the analogous bromide salt (II): no C-H center dot center dot center dot pi or pi-pi interactions were observed and only very weak H-bonds occur between the acidic protons of the imidazolium ring and the halogenated atoms of the anion for Compound Ill. For I and II, water molecules are included in the crystal lattice. Water molecules link the chloride anions in the case of I, but there are no direct interactions between the protons of the imidazolium ring and water molecules, as in the case of compound II. The hydrogen bond network in the case of compound II is formed via water molecules between the cations and the anions. In the case of the hexafluorophosphate salt, classical organization in ail extended network of cations and anions connected together by hydrogen bond was observed. (C) 2008 Elsevier B.V. All rights reserved.