Secondary Bonding Interactions in Some Dichloroanilinium Chlorides

Of the six structures presented here, five involve clearly defined hydrophilic layers built up from classical hydrogen bonding systems. Of three solvent-free structures, 2,4- and 3,5-dichloroanilinium chlorides both form ribbon structures involving annelated R²₄ (8) rings with NH₂ donors (two hydrogen atoms from the positively charged NH₃ groups) and chloride acceptors. The ribbons are linked by weaker interactions to form layers. 2,5-Dichloroanilinium chloride forms a layer structure directly, with rings R³₆ (12) exactly analogous to those previously observed in 2-chloroanilinium chloride. 2,6-Dichloroanilinium chloride methanol solvate forms a different type of ribbon structure, with alternating R²₄ (8) and R⁴₆ 12) rings; the latter involve two chlorides, two NH₂ groups and two methanols. These ribbons too are linked to form layers. 2,3-Dichloroanilinium chloride hydrate forms layers with two types of ring R³₅ (10); one involves two NH₂, two chlorides and the OH part of a water, whereas in the other, an NH₂ is replaced by OH₂. In all these structures the aromatic groups project approximately perpendicular to the layers to form hydrophobic regions; for all except 3,5-dichloroanilinium chloride, neighbouring layers are linked by weaker interactions such as C-H···Cl hydrogen bonds or Cl···Cl contacts. The final structure, 3,5-dichloroanilinium chloride 1/4-hydrate, is completely different; it involves two types of columns, one built up from quadrilaterals of Cl···Cl contacts between cations and the other consisting of “nanotubes ’ of NH₃ groups and chloride anions linked by two- and three-centre hydrogen bonds. The columns are in turn linked by cation-anion Cl···Cl interactions.