Glycinium hydrogen fumarate glycine solvate monohydrate

In the title compound, C2H6NO2 +·C4H3O4 −·C2H5NO2·H2O, the asymmetric unit contains two glycine residues, one protonated and one in the zwitterionic form, a hydrogen fumarate anion and a water molecule. Through N—H⋯O and O—H⋯O hydrogen bonds, molecules assemble in layers parallel to the (10) plane, one layer of hydrogen fumarate anions alternating with two layers of glycine molecules. In each glycine layer, hydrogen bonds generate an R 4 4(19) graph-set motif. Further hydrogen bonds involving the water molecule and the hydrogen fumarate anions result in the formation of a three-dimensional network.

In the title compound, C 2 H 6 NO 2 + ÁC 4 H 3 O 4 À ÁC 2 H 5 NO 2 ÁH 2 O, the asymmetric unit contains two glycine residues, one protonated and one in the zwitterionic form, a hydrogen fumarate anion and a water molecule. Through N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds, molecules assemble in layers parallel to the (101) plane, one layer of hydrogen fumarate anions alternating with two layers of glycine molecules. In each glycine layer, hydrogen bonds generate an R 4 4 (19) graphset motif. Further hydrogen bonds involving the water molecule and the hydrogen fumarate anions result in the formation of a three-dimensional network.

Experimental
The asymmetric unit is built up from two glycine residues, a ionized fumaric acid and a water molecule linked by hydrogen bonds (Fig. 1). One of the glycine residue has been protonated, and the other one is in the zwitterionic form. The fumaric acid molecule is in the ionized state, as expected from the strength of the acid and the required charge neutrality of the salt.
Through N-H···O and O-H···O hydrogen bondings, the molecules assemble in layers parallel to the (1 0 -1) plane, one layer of fumaric acid alternates with two layers of glycine (Fig. 2). In each layer of glycine, the hydrogen bonds generate a graph set motif R 4 4 (19) (Etter, 1990;Bernstein et al., 1994) (Fig.3, Table 1). Further H bonds involving the water and the fumaric acid result in the formation of a three dimensional network (Fig. 2, Table 1). Unlike the other amino acid fumaric acid complexes (Alagar et al., 2003a,b ) there are hydrogen bonds found between the fumaric acid molecules.

Experimental
Colourless single crystals of the complex were grown, as transparent needles by slow evaporation method from a saturated aqueous solution containing glycine and fumaric acid in 1: 1 stoichiometric ratio.

Refinement
H atoms attached to C and N atoms were found in difference Fourier but introduced in calculated position and treated as riding on their parent atoms with C-H= 0.97Å (CH 2 ) or 0.93Å (aromatic) and N-H= 0.89\%A with U iso = 1.2U eq (C) for CH and U iso = 1.5U eq (N). H atoms of water molecule were located in difference Fourier maps and included in the subsequent refinement using restraints (O-H= 0.85 (1)Å and H···H= 1.39 (2)Å) with U iso (H) = 1.5U eq (O).

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
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