Acetoguanamine N,N-dimethylformamide solvate

The structure of acetoguanamine (or 2,4-diamino-6-methyl-1,3,5-triazine) has been determined as the N,N-dimethylformamide solvate, C4H7N5·C3H7NO. The molecular components are associated in the crystal structure to form ribbons stabilized by three N—H⋯N and one N—H⋯O hydrogen bonds which involve NH groups as donors and the N atoms of the heterocyclic ring and the carbonyl O atom of the solvent as acceptors.

The structure of acetoguanamine (or 2,4-diamino-6-methyl-1,3,5-triazine) has been determined as the N,N-dimethylformamide solvate, C 4 H 7 N 5 ÁC 3 H 7 NO. The molecular components are associated in the crystal structure to form ribbons stabilized by three N-HÁ Á ÁN and one N-HÁ Á ÁO hydrogen bonds which involve NH groups as donors and the N atoms of the heterocyclic ring and the carbonyl O atom of the solvent as acceptors.

Comment
As a part of a more general study of multiple-hydrogen-bonding DNA/RNA nucleobases as potential supramolecular reagents (Portalone et al., 1999;Portalone & Colapietro, 2007a, b), this work is a continuation of our studies on crystal adducts of DNA/RNA pyrimidine bases coupled with amino-derivatives of aromatic N-heterocycles via multiple hydrogen bonds to mimic the base-pairing of nucleic acids.
The asymmetric unit of (I) comprises a planar independent molecule of acetoguanamine hydrogen-bonded to N,N-dimethylformamide (DMF) (Fig. 1). A comparison of the molecular geometry of acetoguanamine with that reported for the corresponding molecule in the 1:1 monohydrated molecular adduct formed between acetoguanaminium chloride and acetoguanamine (Portalone & Colapietro, 2007a) shows that the corresponding bond lengths and angles are equal within experimental error. An analysis of the crystal packing of (I) shows ( Table 1) that adjacent molecules of acetoguanamine are linked into ribbons (Fig. 2) by three independent intermolecular N-H···N hydrogen bonds between NH moieties and N atoms of the heterocyclic ring to form hydrogen-bonded rings (one centrosymmetric) of descriptor R 2 2 (8) (Etter et al., 1990;Bernstein et al., 1995;Motherwell et al., 1999). These hydrogen bonds that lead to two-dimensional arrays in the ab plane are bridged by DMF molecules via N-H ···O interactions forming C 1 1 (3) chains.
Experimental Acetoguanamine (0.1 mmol, Sigma Aldrich at 98% purity) was dissolved in N,N-dimethylformamide (9 ml) and heated under reflux for 3 h. After cooling the solution to an ambient temperature, crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation of the solvent after a few days.

Refinement
All H atoms were found in a difference map, positioned with idealized geometry, and refined isotropically using a riding model (N-H = 0.82-0.89 Å, C-H = 0.93-0.97 Å). Their U iso values were kept equal to 1.2U eq (N), 1.5U eq (C), 2.0U eq (C) of the solvent molecule. In the absence of significant anomalous scattering, Friedel pairs were merged. Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacements ellipsoids are at the 50% probability level.

Special details
Geometry. All e.s. 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.