Hydrogen bis[2-(4-ammoniophenoxy)acetate] triiodide

In the title compound, C16H19N2O6 +·I3 −, the carboxylate groups of a pair of (4-aminophenoxy) acetate ligands are bridged by an H atom in a rather classical configuration. The H atom is located on an inversion center and the pair of carboxylate groups are centrosymmetrically related with an O⋯O distance of 2.494 (5) Å. The I3 − anion is also located on an inversion center. In the crystal, N—H⋯O and N—H⋯I hydrogen-bond interactions build up a three-dimensionnal network.

In the title compound, C 16 H 19 N 2 O 6 + ÁI 3 À , the carboxylate groups of a pair of (4-aminophenoxy) acetate ligands are bridged by an H atom in a rather classical configuration. The H atom is located on an inversion center and the pair of carboxylate groups are centrosymmetrically related with an OÁ Á ÁO distance of 2.494 (5) Å . The I 3 À anion is also located on an inversion center. In the crystal, N-HÁ Á ÁO and N-HÁ Á ÁI hydrogen-bond interactions build up a three-dimensionnal network.

Comment
We are interested in the dielectric-ferroelectric materials, including organic ligands (Li et al.,2008), metal-organic coordination compounds (Hang et al., 2009) and organic-inorganic hybrids. Recent studies have revealed that in amino acid-inorganic acid complexes, when the number of H atoms liberated from the inorganic acid is less than the number of amino acids, the H atom is shared by two amino acids, resulting in short symmetric O-H···O hydrogen bonds, as evidenced in triglycine sulfate (Kay et al., 1977), leading to phase transitions. Thus, we want to find aromatic compounds containing amidogens having dielectric-ferroelectric properties. As part of our ongoing studies, we report here the crystal structure of the title compound.
The anion I 3 is also located around inversion center. The occurence of N-H···O and N-H···I hydrogen interactions build up a three dimensionnal network (Fig. 2).
Experimental ethyl 2-(4-aminophenoxy)acetate (1.95 g) and methanol(30 ml) were added to a round-bottomed flask with a magnetic stirrer bar, then hydrofluoric acid(52%) 2.4 g was added into the mixture. Yellow plate-like crystals of (I) were grown from an ethanol solution of the title compound by slow evaporation at room temperature.

Refinement
All H atoms attached to C atoms and N atom were fixed geometrically and treated as riding with C-H = 0.93 Å (aromatic) or 0.97 Å (methylene) and N-H = 0.89 Å with U iso (H) = 1.2U eq (C,N,O). Fig. 1

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.