Hydrogen-bonded assemblies in the molecular crystals of 2,2'-thiodiacetic acid with ethylenediamine and o-phenylenediamine.

Abstract

Carboxylate molecular crystals have been of interest due to the presence of hydrogen bonding, which plays a significant role in chemical and crystal engineering, as well as in supramolecular chemistry. Acid-base adducts possess hydrogen bonds which increase the thermal and mechanical stability of the crystal. 2,2'-Thiodiacetic acid (Tda) is a versatile ligand that has been widely explored, employing its multidendate and chelating coordination abilities with many metals; however, charge-transfer complexes of thiodiacetic acid have not been reported. Two salts, namely ethylenediaminium 2,2'-thiodiacetate, C2H10N22+·C4H4O4S22-, denoted Tdaen, and 2-aminoanilinium 2-(carboxymethylsulfanyl)acetate, C6H9N2+·C4H5O4S-, denoted Tdaophen, were synthesized and characterized by IR, 1H and 13C NMR spectroscopies, and single-crystal X-ray diffraction. In these salts, Tda reacts with the aliphatic (ethylenediamine) and aromatic (o-phenylenediamine) diamines, and deprotonates them to form anions with different valencies and different supramolecular networks. In Tdaen, the divalent Tda2- anions form one-dimensional linear supramolecular chains and these are extended into a three-dimensional sandwich-type supramolecular network by interaction with the ethylenediaminium cations. However, in Tdaophen, the monovalent Tda- anions form one-dimensional zigzag supramolecular chains, which are extended into a three-dimensional supramolecular network by interaction with the 2-aminoanilinium cations. Thus, both three-dimensional structures display different ring motifs. The structures of these diamines, which are influenced by hydrogen-bonded assemblies in the molecular crystals, are discussed in detail.