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, 2,4and 3,5-dichloroanilinium chlorides both form ribbon structures involving annelated R4(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 R6(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 R4(8) and R6(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 R5(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-HþþþCl hydrogen bonds or ClþþþCl contacts. The final structure, 3,5-dichloroanilinium chloride /4-hydrate, is completely different; it involves two types of columns, one built up from quadrilaterals of ClþþþCl contacts between cations and the other consisting of “nanotubes’ of NH3 groups and chloride anions linked by twoand three-centre hydrogen bonds. The columns are in turn linked by cation-anion ClþþþCl interactions.