Aminoguanidinium hydrogen succinate

The title compound, CH7N4 +·C4H5O4 −, is a molecular salt containing discrete aminoguanidinium and succinate ions. The aminoguanidinium cation is nearly planar, with a maximum deviation of 0.035 (1) Å. The dihedral angle between the aminoguanidinium cation and the succinate anion is 3.35 (6)°. The crystal packing exhibits intermolecular N—H⋯O and O—H⋯·O hydrogen bonds.

The title compound, CH 7 N 4 + ÁC 4 H 5 O 4 À , is a molecular salt containing discrete aminoguanidinium and succinate ions. The aminoguanidinium cation is nearly planar, with a maximum deviation of 0.035 (1) Å . The dihedral angle between the aminoguanidinium cation and the succinate anion is 3.35 (6) . The crystal packing exhibits intermolecular N-HÁ Á ÁO and O-HÁ Á ÁÁO hydrogen bonds.

Comment
Aminoguanadine is an early inhibitor of Advanced Glycosylation End products (AGEs) (Makita et al., 1995). It helps prevent proteins cross-linking and is being used in diabetes, atherosclerosis, renal and aging disorders (Brownlee et al., 1986).
Aminoguanadine is a highly reactive nucleophilic reagent that reacts with many biological molecules (Pyridoxal phosphate, Pyruvate, glucose, malondialdehyde, and others). The crystal structures of several guanidinium salts have previously been reported over the last three decades (Adams, 1977;Mullen & Hellner, 1978). Here We report the crystal structure of the title compound, aminoguanidinium hydrogensuccinate (I) (Fig. 1).
The aminoguanidinium is nearly planar, with atom N11 shows the maximum deviation from planarity 0.035 (1) Å. The bond lengths in (I) are normal and comparable with the corresponding values observed in the related structure (Akella & Keszler, 1994). The dihedral angle between the aminoguanidinium cation and succinate anion is 3.35 (6)°. Two main motifs dominate the hydrogen bond in (I). Firstly, a nearly symmetrical simple R 2 2 (8) ring (Bernstein et al., 1995) forms from hydrogen bond between the two molecules involving the two guanidinium amino groups and the two succinate O atoms, viz. N10-H10B···O9 and N11-H11···O8 (Table 1 and Fig. 2). Secondly, atom N12 and N10 in the molecule at (x, y, z) donate one proton each to atom O6 and O7 in the molecule at (-1/2 + x, 1/2 -y, -1/2 + z), generating R 2 2 (8) ring motif (Table   1 and Fig. 2). Also, the O-H···O interaction is observed (Table 1). Thus, the symmetry-related molecules are cross linked by these hydrogen bonds to generate a three-dimensional network.

Experimental
Aminoguanidine bicarbonate (0.136 g; 0.001 mol) was added in small portions with stirring to an aqueous solution (30 ml) of succinic acid (0.118 g; 0.001 mol). The resulting clear solution of pH<2 was concentrated over water-bath to half of its volume. The transparent single crystals suitable for X-ray diffraction obtained by slow evaporation at room temperature were separated, washed with ethanol and air dried.

Refinement
All N bound H atoms were located in a difference map and refined freely. All other H atoms were fixed geometrically and

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 > 2sigma(F 2 ) is used only for calculating R-factors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq H12A 0.1707 (