Creatinium perchlorate

The title compound, C4H8N3O+·ClO4 −, is built up from creatininium cations and perchlorate anions. Crystal cohesion and perchlorate stability are ensured by N—H⋯O hydrogen bonds that together with weak C—H⋯O interactions build up a three-dimensional network.

The title compound, C 4 H 8 N 3 O + ÁClO 4 À , is built up from creatininium cations and perchlorate anions. Crystal cohesion and perchlorate stability are ensured by N-HÁ Á ÁO hydrogen bonds that together with weak C-HÁ Á ÁO interactions build up a three-dimensional network.

Comment
Studies of organic-inorganic hybrid materials, including amino acids and various inorganic acids (Benali-Cherif et al., 2004), have received a great deal of attention in recent years, because of their electrical, magnetic and optical properties (Kagan et al., 1999;Hill, 1998).
Creatinine is formed by the metabolism of phosphocreatine, a high-energy molecule which provides a rapid supply of ATP to muscles. Phosphocreatine is converted spontaneously to creatinine on a regular basis. Consequently, creatinine is released into the blood and excreted by the kidneys as a metabolic waste product.
The present structure analysis of creatininium perchlorate, (I), was undertaken as part of a more general investigation into the nature of hydrogen bonding between organic bases or amino acids and inorganic acids in their crystalline forms (Cherouana et al., 2003).
In the present study, only the imino group of the imidazolyl moiety (atom N1) in creatinine is protonated, which confirms the possibility of the existence of creatininium cations in various tautomeric forms in aqueous solution. This is discussed and quantified in the light of the interpretation of the solution acidity effect on 1H, 13 C and 14 N NMR chemical shifts (Kotsyubynskyy et al., 2004).
The asymmetric unit of (I) contains a monoprotonated creatininium cation and two perchlorate anions (Fig.1).
The bond distances in the imidazolyl ring of (I) are, in general, not significantly different from those found in similar hybrid compounds containing protonated imidazolyl moieties like creatininium nitrate (Berrah et al., 2005). The creatininium ring is planar, as expected, with a mean deviation from planarity of 0.0017 Å.
The average Cl-O bond distances and O-Cl-O bond angles are 1.40625 (4) Å and 109.50 (3)°, respectively, confirming a tetrahedral configuration, similar to other perchlorates studied at low temperature. Perchlorate anions (ClO 4 -), surrounded by two creatininium residues via hydrogen bonds play an important role in stabilizing the crystal structure.
The cation-anion N-H-O interactions form sheet parallel to the (0 1 0) plane (Table 1, Fig.2). Weak C-H···O interactions further link the sheets to form a three dimensionnal network (Table 1).

Experimental
The title compound (I) was cristallized by slow evaporation at room temperature of an aqueous solution of creatinine and perchloric acid in a 1:1 stochiometric ratio.

Refinement
The title compound crystallizes in the centrosymmetric space group P2 1 /n. All non-H atoms were refined with anisotropic atomic displacement parameters. All H-atoms of the cation entities were located in difference Fourier syntheses and refined as riding model with C-H and N-H bond lengths constrained to 0.96-0.97 Å and 0.834 Å, respectively.  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.