The crystal packing modes of butane-1,4-diamine salts with acetic, di- and trichloroacetic acids at 100Â K

The crystal structures of three salts of butane-1,4-diamine: acetate ((C4H14N22+ · 2(C2H3O2)−), dichloroacetate ((C4H14N22+ · 2(C2HCl2O2)−) and trichloroacetate ((C4H14N22+ · 2(C2Cl3O2)−) were determined by X-ray diffraction at 100 K. In all these cases the dication is either symmetrical and situated at the inversion center or disordered about the inversion center, in the P21/c space group. The conformation of dication is ttt (t-trans) for acetate and trichloroacetate, or tg−t and tg+t (g-gauche) - for dichloroacetate, and this last salt undergoes the phase transition in higher temperature. The role of covalently bonded chlorine atoms in the determination of the crystal packing, at least in this case, is only the secondary one. The potential halogen bonds or NH⋯Cl hydrogen bonds do not compete successfully with the NH⋯O hydrogen bonds of different strength which - along with the coulombic interactions between the charged species - are certainly the main driving force of the crystal packing along this series of compounds. The different packing modes are pronounced in relative cation-dication arrangement in the layer structure.