Crystal structure of polymeric sodium 4-carboxyphenoxyacetate dihydrate

Abstract

The crystal structure of a hydrated sodium salt of 4-carboxyphenoxyacetic acid (PCPAH), also known by its IUPAC name of 4-carboxymethoxybenzoic acid, has been determined by X-ray diffraction and refined toR=0.040 for 2013 observed MoKα reflections. The title polymeric complex, [Na(PCPA)(H₂O)₂]_n, is triclinic, space groupP¯1, witha=5.309(1),b=5.886(1),c=17.280(1) Å,α=83.72(1),β=88.86(1),γ=84.57(1)°, andZ=2. The coordination geometry about the Na atom is a distorted octahedron [Na-O, 2.310(2) to 2.523(1) Å], with three oxygens from two oxyacetate groups and three oxygens of aqua ligands at its corners. The bridging oxyacetate moieties and aqua ligands connect the sodium centers into one-dimensional chains, and hydrogen bonds formed between pairs of centrosymmetrically-related carboxyl groups join the chains into two-dimensional thick layers, which approximately correspond to the (¯204) family of planes. Finally, hydrogen bonds formed between oxygen atoms of the PCPA and aqua ligands link the thick layers into a three-dimensional network.