(4-Hydroxy-3-nitrobenzyl)methylammonium chloride

The title compound, C8H11N2O3 +·Cl−, was synthesized as an intermediate in the development of a new sugar sensor. The structure displays N—H⋯Cl and O—H⋯O hydrogen bonding, as well as weak O—H⋯Cl interactions and π–π stacking (3.298 Å). There are two formula units in the asymmetric unit.


S1. Comment
The title compound, (I), was synthesized as an intermediate in the development of a new sugar sensor (James et al., 1995). The compound itself is also novel and is being reported for the first time.
The structure consists of two molecules in the asymmetric unit ( Figure 1). The cation consists of a planar nitro phenol ring with a methylaminomethyl group in the para position with respect to the hydroxy group (O1) on the ring. The methylammonium groups attached to the methylene carbon (C7) deviate from the plane of the ring with a torsion angle of -121.52 (13)° for C3A-C4A-C7A-N2A and -46.81 (16)° for C3B-C4B-C7B-N2B.
The structure exhibits both intermolecular (N1-H1···Cl) and intramolecular (O1-H1···O2) hydrogen bonding interactions (Table 1, Figure 2). The chloride ions act as hydrogen bond acceptors between adjacent molecules. Weak interactions are also observed between O1-H1···Cl1. These interactions, with a bond length of 2.87Å (O1A-H1A···Cl1B i ), are more likely weak Van der Waals interactions rather than true hydrogen bonds. See Table 1 for a full list of all hydrogen bond interactions. An interdigitated, layered structure is observed with the aromatic groups π-π stacking above each other and the methylaminomethyl group interacting with the chloride ions in hydrogen bonded layers ( Figure   3).

S3. Refinement
Hydrogen atoms were located in the difference map then positioned geometrically, and allowed to ride on their respective parent atoms, with bond lengths of 0.99Å (CH 2 ), 0.98Å (CH 3 ), 0.95Å (CH), 0.98Å (NH 2 ) or 0.84Å (OH). Isotropic displacement parameters for these atoms were set equal to 1.2 (CH 2 , CH and NH 2 ), or 1.5 (CH 3 and OH) times U eq of the parent atom.  The asymmetric unit showing ellipsoids at the 50% probability level and the numbering scheme employed.

Figure 2
Diagram of the inter-and intramolecular hydrogen bonding. Hydrogen atoms have been omitted for clarity.  Depiction of the packing. Hydrogen atoms have been omitted for clarity.

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