Crystal structure and Hirshfeld surface analysis of 2,4-diamino-6-methyl-1,3,5-triazin-1-ium trichloroacetate monohydrate

In the crystal structure, the cations form hydrogen-bonded zigzag chains through centrosymmetric cyclic (8) N—H⋯N associations while the water molecule acts as a double acceptor, linking the cations of the chain peripherally through amine N—H⋯O hydrogen bonds, closing cyclic (8) motifs, and as a double O—H⋯O donor, linking the anions, giving an overall three-dimensional structure.

The asymmetric unit of the title molecular salt, C 4 H 8 N 5 + ÁC 2 Cl 3 O 2 À ÁH 2 O, coomprises a 2,4-diamino-6-methyl-1,3,5-triazin-1-ium cation, a trichloroacetate anion and a water molecule of solvation. The protonated N atom of the cation forms a hydrogen bond with a carboxyl O atom of the anion, which also acts as a hydrogen-atom acceptor with the water molecule. The cations form centrosymmetric dimeric units through R 2 2 (8) N-HÁ Á ÁN bond pairs and are extended into zigzag chains along the c-axis direction, also through similar cyclic R 2 2 (8) dual N-HÁ Á ÁN hydrogen-bonding interactions. The water molecule acts as a dual acceptor forming N-HÁ Á ÁO hydrogen bonds between the amine groups of the cations, forming cyclic R 2

Chemical context
Triazine heterocyclic -conjugated structures are attractive owing to the chemical flexiblity of their systems and have many applications in medicinal chemistry, materials science and organic synthesis (Boesveld & Lappert, 1997;Boesveld et al., 1999;Reid et al., 2011). 1,3,5-Triazine derivatives represent an important class of compounds because of their potential to be biologically active. They are known to be anti-protozoal agents (Baliani et al., 2005), anticancer agents (Menicagli et al., 2004), estrogen receptor modulators (Henke et al., 2002), antimalarials (Agarwal et al., 2005), cyclin-dependent kinase modulators (Kuo et al., 2005) and anti-microbial agents (Koc et al., 2010). These compounds still continue to be the object of considerable interest mainly because of their applications in various fields, including the production of herbicides and polymer photostabilizers. Triazine derivatives have been used as building blocks for subtle chemical architectures comprising organic-inorganic hybrid frameworks (Mathias et al., 1994;MacDonald & Whitesides, 1994;Guru Row, 1999;Krische & Lehn, 2000;Sherrington & Taskinen, 2001). In these approaches, interplay between molecules is achieved by using diverse styles of non-covalent interactions, which include hydrogen bonds or ionic, hydro-phobic, van der Waals or dispersive forces. Herein, the crystal structure of the title compound salt, 2,4-diamino-6-methyl-1,3,5-triazine-5-ium trichloroacetate monohydrate is reported. Hirshfeld surface analysis and 2D fingerprint plots were employed in order to quantify the contributions of the various intermolecular interactions present in the structure.

Figure 2
A packing view showing the centrosymmetric N-HÁ Á ÁN hydrogenbonded cation pairs with TCA anions, extending into chains along the caxis direction. Water molecules are omitted.  Two-dimensional fingerprint plots for the title compound An overall view of the three-dimensional hydrogen-bonded supramolecular structure.

Synthesis and crystallization
The title compound was prepared by mixing a hot methanolic solution (20 ml) of 2,4-diamino-6-methyl-1,3,5-triazine (1.25 mg) and an aqueous solution (10 ml) of trichloroacetic acid (1.63 mg) in a 1:1 molar ratio. The reaction mixture was warmed over a water bath for a few minutes. The resultant solution was then allowed to cool slowly at room temperature. After a few days, colourless block-shaped crystals of the title compound were separated out.

2,4-Diamino-6-methyl-1,3,5-triazin-1-ium trichloroacetate monohydrate
Crystal data Hydrogen site location: inferred from neighbouring sites H atoms treated by a mixture of independent and constrained refinement w = 1/[σ 2 (F o 2 ) + (0.0984P) 2 + 1.9287P] where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.68 e Å −3 Δρ min = −0.59 e Å −3 Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > 2sigma(F 2 ) is used only for calculating -R-factor-obs 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.