Sulfates of organic diamines: hydrogen-bonded structures and properties

Abstract

In order to investigate the supramolecular hydrogen-bonded networks and other structural features exhibited by compounds containing an organic cation and an inorganic anion, sulfates of the organic diamines, ethylenediamine (I), 1,3-diaminopropane (II), piperazine (III), and 1,4-diazabicyclo[2.2.2]octane (DABCO) (IV) have been prepared investigated by X-ray crystallography. While II, III, and IV crystallize in the centrosymmetric space group, Pbca, P2₁/n, Pbcn, respectively, I crystallizes in the non-centrosymmetric space group, P4₁ exhibiting chirality and weak NLO properties. I-IV exhibit different types of supramolecular H-bonded networks involving the organic cation and the SO²⁻₄ anion. The nature and strength of the H-bonding network vary from one compound to another, with the strongest network found in piperazinium sulfate, III, and the weakest in II. While in III, water molecules form part of the H-bonded network, they are present as guest molecules in the channels of IV. Thermal stability of the compounds as well as the infrared spectra reflect the stabilities of these H-bonded solids.