Graphene-like nets of hydrogen-bonded water molecules in the dihydrate of 2-[(2-ammonioethyl)amino]acetate and the structure of its anhydrous hydroiodide salt

Abstract

2-[(2-Ammonioethyl)amino]acetate dihydrate, better known as N-(2-aminoethyl)glycine dihydrate, C(4)H(10)N(2)O(2) x 2 H(2)O, (I), crystallizes as a three-dimensional hydrogen-bonded network. Amino acid molecules form layers in the ac plane separated by layers of water molecules, which form a hydrogen-bonded two-dimensional net composed of fused six-membered rings having boat conformations. The crystal structure of the corresponding hydroiodide salt, namely 2-[(2-ammonioethyl)ammonio]acetate iodide, C(4)H(11)N(2)O(2)(+) x I(-), (II), has also been determined. The structure of (II) does not accommodate any solvent water molecules, and displays stacks of amino acid molecules parallel to the a axis, with iodide ions located in channels, resulting in an overall three-dimensional hydrogen-bonded network structure. N-(2-Aminoethyl)glycine is a molecule of considerable biological interest, since its polyamide derivative forms the backbone in the DNA mimic peptide nucleic acid (PNA).

From polygons to polyhedra through intermediate structures. A shape measures study of six-atom inorganic rings and clusters

“…18b). Another example is provided by the crystal structure of the zwitterionic 2-[(2-ammonioethyl)amino]acetate dihydrate, 101 in which the hydration molecules form layers of fused boats, hydrogen-bonded above and below to the carboxylate groups (Fig. 18c).…”

“…18 Hexawater groups with boat conformation: (a) independent and connected to an organic molecule by further hydrogen bonding, and fused together forming (b) chains 100 and (c) layers. 101 All connecting lines indicate hydrogen bonds; hydrogen atoms are omitted for clarity and non-water oxygen atoms are depicted in brown.…”