Aminoguanidinium hydrogen fumarate

The title compound, CH7N4 +·C4H3O4 −, is a molecular salt in which the aminoguanidinium cations and fumarate monoanions are close to planar, with maximum deviations of 0.011 (1) and 0.177 (1) Å, respectively. The crystal packing is stabilized by intermolecular N—H⋯O and O—H⋯O hydrogen bonds.

The title compound, CH 7 N 4 + ÁC 4 H 3 O 4 À , is a molecular salt in which the aminoguanidinium cations and fumarate monoanions are close to planar, with maximum deviations of 0.011 (1) and 0.177 (1) Å , respectively. The crystal packing is stabilized by intermolecular N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds.

Comment
Aminoguanadine is an early inhibitor of advanced glycosylation end products (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 nucleophillic 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 hydrogenfumarate, (I), (Fig. 1). In the molecular salt (I), the aminoguanidinium cation and fumarate anion each are nearly planar, with maximum deviations of -0.011 (1) Å and -0.177 (1) Å for atom N12 and O7, respectively ( Fig. 1). The bond lengths in (I) are comparable with the corresponding values observed in related structures (Akella & Keszler , 1994). The angle between the best planes of the aminoguanidinium cation and the fumarate anion is 12.78 (6)°. Atom N10 and N11 in the molecule at (x, y, z) donate one proton each to the atoms O7 and O6 in the molecule at (-1+x, 3/2-y, -1/2+z), generating a R 2 2 (8) ring motif (Table 1 and Fig. 2). Also, an 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
Needle-shaped single crystals of aminoguanidium hydrogenfumarate were prepared by slow evaporation of the aqueous solution obtained by dissolving of aminoguanidinium hydrogencarbonate (0.136g; 0.001mol) in fumaric acid (0.116 g; 1 mmol) solution (30 mL) at ambient condition. Colourless single crystals suitable for X-ray diffraction obtained after four days were collected, 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 allowed to ride on their parent atoms, with distances of O-H = 0.82Å and C-H = 0.93Å with U iso (H)= 1.2U eq . Fig. 1. The molecular structure of the ions present in compound (I) showing 50% probability displacement ellipsoids.

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.  (5) 0.0599 (7) 0.0021 (4) 0.0260 (5) 0.0052 (4)  N13 0.0345 (6) 0.0348 (6) 0.0638 (9) 0.0076 (5) 0.0244 (6) 0.0025 (6) Geometric parameters (Å, °)