N-{3-[(2-Ammonioethyl)amino]propyl}ethane-1,2-diaminium tris(trifluoromethanesulfonate): a salt of a folded triply protonated tetramine.

The structure of a trifluoromethanesulfonate salt of a nontypical triply protonated linear tetramine, C(7)H(23)N(4)(3+).3CF(3)SO(3)(-), with a layered crystal structure is presented. One N atom remains unprotonated. The conformation of the cation is enforced by intra- and intermolecular hydrogen bonds. The crystal structure is built of ca 10 A deep layers, within which cations and anions are hydrogen bonded. Each layer is only weakly bound to its neighbours. This study shows a rare example of an unsymmetrically protonated polyamine and the relation between the lack of protonation, intramolecular hydrogen bonding and the conformation of the cation.