Dopaminium nitrate

The asymmetric unit of the title salt [systematic name: 2-(3,4-dihydroxyphenyl)ethanaminium nitrate], C8H12NO2 +·NO3 −, contains two independent cations and two independent nitrate anions. The crystal structure consists of discrete nitrate ions stacked in layers parallel to (010). These layers are linked via the dopaminium cations by O—H⋯O, N—H⋯O and weak C—H⋯O hydrogen bonds, forming a three-dimensional supramolecular network.

Supporting information for this paper is available from the IUCr electronic archives (Reference: BG2526).

Introduction
Dopamine is an important regulator of many physiological functions, including control of locomotion, cognition, affect, and neuroendocrine hormone secretion. The dopamine transporter (DAT) plays an important role in calibrating the duration and intensity of dopamine neurotransmission in the central nervous system (Jones et al., 1999). In addition, dopamine is an important signal transmitter between the neurons and muscles (Salamone & Correa, 2002).

Synthesis and crystallization
An aqueous solution containing 1 mmol of HNO 3 in 10 ml of water was added to 1 mmol of dopamine hydrochloride in 10 ml of water. The obtained solution was stirred for 15 min and then left to stand at room temperature. Colorless single crystals of the title compound were obtained after some days.

Refinement
The hydrogen atoms bonded to oxygen and nitrogen atoms were located from a difference map and were allowed to refine. The rest of the H atoms were treated as riding, with C-H = 0.97 Å (methylene), or 0.93 Å (methine), with U iso (H) = 1.2U eq (C).

Results and discussion
In this work, we report the preparation and the structural investigation of the dopaminium nitrate, C 8 H 12 NO 2 ·NO 3 (I).
The asymmetric unit of (I) is composed of two independent dopaminium cations and two independent nitrate anions ( Figure 1). The structure of the compound consists of discrete nitrate ions stacked in layers parallel to the (010) plane separated by organic cations (Figure 2). The structural cohesion is established by a three-dimensional network of N-H···O, O-H···O and weak C-H···O hydrogen bonds (Brown, 1976;Blessing, 1986).
Interatomic bond lengths and angles of the nitrate anions spread respectively within the ranges [1.2448 (16)-1.2596 (15) Å] and [119.50 (12)-120.87 (12)°]. These geometrical features have also been noticed in other crystal structures (Marouani et al., 2012;Kefi et al., 2013;Gatfaoui et al., 2013Gatfaoui et al., , 2014aGatfaoui et al., , 2014b. In this atomic arrangement two independent dopaminium cations are present. Examination of the organic cations shows that the bond distances and angles show no significant difference from those obtained in other salt involving the same organic groups (Boghaei et al., 2008). The aromatic rings are planar with an average deviation of 0.0014 Å and form a dihedral angle of 7.81°. The interplanar distance between nearby phenyl rings is in the vicinity of 4.16 Å, a bit longer than required for a medium strength π-π interaction (Janiak, 2000).
The established H-bonds of types O-H···O, N-H···O and C-H···O (Table 1)   An ellipsoid plot of (I) with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.  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. 0.0259 (7) 0.0199 (7) 0.0138 (7) −0.0030 (6) 0.0021 (6) −0.0033 (6)  C16 0.0242 (7) 0.0164 (7) 0.0203 (8) −0.0033 (6) 0.0029 (6) 0.0005 (6) Geometric parameters (Å, º)