Received 23 May 2006
In the title compound, C6H9N3·C7H6O3, the 2-amino-4,6-dimethylpyrimidine and 4-hydroxybenzoic acid molecules link together via N-HO and O-HN hydrogen bonds to form an eight-membered R22(8) ring. Further hydrogen bonds and C-HO interactions result in the formation of a three-dimensional network.
The crystal structures of various aminopyrimidine carboxylates (Hu et al., 2002) and cocrystals (Chinnakali et al., 1999) have been described. From our laboratory, the crystal structures of 2-amino-4,6-dimethylpyrimidinium bromide 2-amino-4,6-dimethylpyrimidine monohydrate (Panneerselvam et al., 2004) and 2-amino-4,6-dimethylpyrimidine cinnamic acid (1/2) (Balasubramani et al., 2005) have been reported. In this paper, the hydrogen-bonding patterns in the title compound, (I), are described.
The asymmetric unit of (I) contains a 2-amino-4,6-dimethylpyrimidine (AMPY) molecule and a 4-hydroxybenzoic (4-HBZ) acid molecule (Fig. 1). Both species are neutral, thus (I) is an adduct rather than a molecular salt. Atoms O2 and the -N2H2 group act as hydrogen-bond donors to atoms N1 and O3, respectively, to form an eight-membered ring, which has the graph-set notation R22(8) (Etter, 1990; Bernstein et al., 1995). This type of interaction has been observed in the crystal structures of other 2-aminopyrimidine-carboxylic acid adducts (Lynch & Jones, 2004).
The second H atom of the 2-amino group links to an O2 atom in an adjacent molecule via an N-HO bond, and one of the C atoms (C11) of 4-HBZ is hydrogen bonded to O3 via a C-HO interaction to form a ring having graph-set notation R23(8), leading to the supramolecular chain shown in Fig. 2. Hence, O3 acts as a bifurcated acceptor. The 4-HBZ hydroxy (O1) group is hydrogen bonded to pyrimidine atom N3 via an O-HN interaction, to form a chain as shown in Fig. 3.
Aromatic - interactions between the pyrimidine ring of AMPY and the benzene ring of 4-HBZ are also observed in (I). The perpendicular separation is 3.552 Å, and the centroid-to-centroid distance is 3.660 (9) Å. The slip angle (the angle between the centroid-to-centroid vector and the normal to the plane) is 19.86°. These values are typical for aromatic - stacking interactions (Hunter, 1994).
| || Figure 1 |
ORTEPII (Johnson, 1976) view of the asymmetric unit of (I), showing 50% probability displacement ellipsoids. Dashed lines indicate hydrogen bonds.
| || Figure 2 |
A view of the supramolecular chain in (I). Dashed lines indicate hydrogen bonds and H atoms not involved in hydrogen bonding have been omitted. [Symmetry codes: (ii) x, -y, + z; (iii) x, -y, z - .]
| || Figure 3 |
A view of the hydrogen-bonding patterns in (I). Dashed lines indicate hydrogen bonds and H atoms not involved in hydrogen bonding have been omitted. [Symmetry code: (i) 1 + x, -y, z - .]
Hot methanol solutions (20 ml) of 2-amino-4,6-dimethylpyrimidine (30 mg, Aldrich) and 4-hydroxybenzoic acid (32 mg, LOBA Chemie, India) were mixed and warmed over a water bath for a few minutes. The resulting solution was allowed to cool slowly at room temperature. Crystals of (I) appeared from the mother liquor after a few days.
In the absence of significant anomalous scattering effects, Friedel pairs were averaged. All the H atoms were positioned geometrically (C-H = 0.93-0.96 Å, N-H = 0.86 Å and O-H = 0.82 Å) and refined as riding, with Uiso(H) = 1.2Ueq(carrier).
Data collection: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998); cell refinement: DENZO and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003) and ORTEPII (Johnson, 1976); software used to prepare material for publication: PLATON.
DL thanks the EPSRC National Crystallography Service (Southampton, England) for the X-ray data collection.
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