The Role of Host Molecules in the Crystalline Inclusion Compounds: Hexamethylenebis(trimethylammonium) dications as guest species

Abstract

Two new inclusion compounds, namely (CH3)3N+(CH2)6N+(CH3)3·2Br–·2(NH2)2CS (1), and (CH3)3N+(CH2)6N+(CH3)3·2(p-HOC6H4COO–)·2(NH2)2CS (2), have been prepared and characterized by X-ray crystallography. In the crystal structure of 1, tetramers comprising pairs of thiourea molecules and bromide anions by N—H⋅⋅⋅S and N—H⋅⋅⋅Br hydrogen bonds are joined with the methyl groups of hexamethylenebis(trimethylammonium) dications to generate a layered 3D structure. Compound 2 exhibits a channel-type host lattice with channels of rectangular cross-section running parallel to the a axis, which are generated by N—H⋅⋅⋅O and N—H⋅⋅⋅S hydrogen bonds between p-hydroxybenzoic anions and thiourea molecules, and the hexamethylenebis(trimethylammonium) dications are arranged separately in each channel. By comparing these two inclusion compounds, the structural difference of the two inclusion compounds is due to the addition of p-hydroxybenzoic acid as the host molecule in the 2. The weak hydrogen bonds have an important role in lattice construction.