1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-aminium 2-hydroxybenzoate

In the title salt, C11H14N3O+·C7H5O3 −, the phenyl ring of the cation is oriented at an angle of 67.0 (1)° with respect to the five-membered pyrazolone ring. The carboxylate plane of the anion is twisted out from the plane of the aromatic ring at an angle of 13.7 (3)°. In the crystal, the cations form hydrogen-bonded dimers with an R 2 2(10) ring motif. The salicylate anion has an intramolecular O—H⋯O hydrogen bond.

In the title salt, C 11 H 14 N 3 O + ÁC 7 H 5 O 3 À , the phenyl ring of the cation is oriented at an angle of 67.0 (1) with respect to the five-membered pyrazolone ring. The carboxylate plane of the anion is twisted out from the plane of the aromatic ring at an angle of 13.7 (3) . In the crystal, the cations form hydrogenbonded dimers with an R 2 2 (10) ring motif. The salicylate anion has an intramolecular O-HÁ Á ÁO hydrogen bond.

D-HÁ
Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL/PC (Sheldrick, 2008); program(s) used to refine structure: SHELXTL/PC; molecular graphics: Mercury (Macrae et al., 2006 ) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXTL/PC. SAB sincerely thanks the Vice-Chancellor and Management of Kalasalingam University, Anand Nagar, Krishnan Koil, for their support and encouragement. SA thanks the Vice-Chancellor of Anna University Tirunelveli for his support and encouragement. logical activity, especially in the class of nonsteroidal antiinflammatory agents used in the treatment of arthritis and other musculo skeletal and joint disorders. Pyrazolone derivatives, as lactam structure related compounds, are also widely used in preparing dyes and pigments. 4-aminoantipyrene and its derivatives have potential biological activities (Jain et al., 2003).
Analgesic and antiinflammatory activities of the 4-aminoantipyrene complexes were extensively studied and reported (Filho et al., 1998;Sondhi et al., 1999). Apart from that, antimicrobial and anticancer activity of the 4-aminoantipyrine derivatives and their metal complexes caught the attention of many researchers during last decade (Mishra, 1999;Sondhi et al., 2001). Intermolecular forces also play very essential role in the formation of supramolecular organic systems. The phenomenon of hydrogen bonding enlightens the area of molecular recognition, crystal-engineering research and organic synthons for supramolecular research (Desiraju, 1989). Carboxylic acids and amines are two commonly used functional groups in crystal engineering because they generally form robust architectures via O-H···O and N-H···O hydrogen-bonded interactions (Etter et al., 1990). 4-aminoantipyrene is one of the such important ligands since it has potential sites for hydrogen bonding interactions, viz., the amine N atom (as donor) and carbonyl O atom (as acceptor). Consideration of these above specifics and to study the supramolecular geometry through hydrogen bonding extensions, the present investigation was undertaken. 4-aminoantipyrene was treated with salicylic acid and the title compound is crystallized.
The asymmetric unit of (I) consists of one single charged protonated 4-aminoantipyrene cation and a deprotonated salicylate anion (Fig 1). Interatomic distances and angles are normal and in good agreement with the similar structures (Allen, 2002). The expected proton transfer from salicylic acid to 4-aminoantipyrene is established at N5 atom. The protonation on the N site of the cation is evidenced from the elongated C-N bond distance and the deprotonation on anion is confirmed from the COOsymmetric bond distances (Table 1). The phenyl ring of the cation is oriented with an angle of 67.0 (1)° to the five membered pyrazolone ring. Also, in the asymmeric unit, the phenyl ring of the cation is making a dihedral angle of 87.5 (1)° with the phenyl ring of the anion. The carboxylate plane of the salicylate anion is twisted from the plane of the aromatic ring with an angle of 13.7 (3)°. The twisting of carboxylate plane can be associated with the hydrogen bonding interactions of amino group of the cation. Due to the packing specificity of the crystal, one of the methyl atoms (C22) of the cation is slightly out of plane of the five-membered pyrzalone ring with the distance of 0.542 (3) Å.
supplementary materials sup-2 The most elegant aspect of the present work is found not only in the molecular structure but also in the crystal packing via N-H···O and O-H···O hydrogen bonds. Fig. 2 shows the aggregation of the molecules around the inversion centres of the unit cell through ring motifs. As a characterestic H-bond, salicylate anion consists a self associated intramolecular S(6) motif through O-H···O hydrogen bond. The amino group of the cation is involved in two two-centered and one three-centered hydrogen bonds. The amino and carbonyl O atom of the cation is involving in N-H···O hydrogen bond which leads to a classical molecular dimerization through the ring R 2 2 (10) motif around the inversion center of the unit cell (Fig. 3). Other two H atoms of amino group are involved in N-H···O hydrogen bonds with the adjascent salicylate anions. This leads to another ring R 4 2 (8) motif formed through two cations and two anions (Fig. 4). This ring motif is further accompanied with another adajascent ring R 1 2 (4) motif through the bifuracted (two-centered) hydrogen bond. These three intermolecular ring motifs are intersected and extending along the a axis of the unit cell. This leads to hydrophilic region at the plane y=1/2 which are sanwitched between the hydrophobic regions at y=1/4 and 3/4.

Experimental
The title compound was crystallized from the aqueous mixtures of 4-aminoantipyrene with salicylic acid, in the stochiometric ratio of 1:1 at room temperature by the technique of slow evaporation.