Crystalline Inclusion Compounds: Thiourea and Bis-quaternary Ammonium Salts

Abstract

Two new inclusion compounds, namely 3(CH₃)₃N⁺(CH₂)₃N⁺(CH₃)₃·6Br^–·8(NH₂)₂CS·H₂O (1) and (CH₃)₃N⁺(CH₂)₄N⁺(CH₃)₃·2Br^–·2(NH₂)₂CS (2), have been prepared and characterized by X-ray crystallography. In the crystal structure of 1, uni-directional double channels with peanut-shaped cross-section running paralleling to the a axis are generated by N–H···S and N–H···Br hydrogen bonds between thiourea molecules and bromide anions, and trimethylenebis(trimethylammonium) dications are arranged separately in each hemisphere of the double channel. In 2, 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 tetramethylenebis(trimethylammonium) dications to generate similar quasi-rectangle channels. The present study shows that new anionic host lattices can be constructed from thiourea molecules and bromide anions as building blocks, which readily adopt different topologies for the accommodation of bis-quaternary ammonium dications of various sizes. Hydrogen bonding constitutes a principal driving force that dominates the crystal packing of the two compounds, in which weak hydrogen bonds are of particular significance in the construction.

Graphical Abstract

In the crystal structure of 1, uni-directional double channels with peanut-shaped cross-section running paralleling to the a axis are generated by N–H···S and N–H···Br hydrogen bonds between thiourea molecules and bromide anions, and trimethylenebis(trimethylammonium) dications are arranged separately in each hemisphere of the double channel. In 2, 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 tetramethylenebis(trimethylammonium) dications to generate similar quasi-rectangle channels.