Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. H atoms attached to carbon atoms were positioned geometrically and constrained to ride on their parent atoms. C—H bond distances were constrained to 0.95 Å for aromatic and alkene C—H moieties, and to 0.98 Å for CH3 moieties, respectively. The N—H proton hydrogen bonding between atoms N1 and N3 was found to be disordered and was refined as split between two positions. The H atoms were assigned as bonded to a planar (sp2 hybridized) N atom, respectively with fixed bond angles and torsion angles, but the N—H bond distances were allowed to refine to account for asymmetry induced by charge and hydrogen bonding (AFIX 44 command). N—H distances refined to 0.83 (5) for N1—H1 and to 0.89 (2) for N3—H3, occupancies refined to 0.33 (2) for H1 and 0.67 (2) for H3. Methyl CH3 were allowed to rotate but not to tip to best fit the experimental electron density. Uiso(H) values were set to a multiple of Ueq(C/N) with 1.5 for CH3 and 1.2 for C—H and NH+, respectively.