organic compounds
5-Amino-1H-1,2,4-triazol-4-ium-3-carboxylate hemihydrate
aDepartment of Chemistry, University of Aveiro, CICECO, 3810-193 Aveiro, Portugal, bREQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto, Portugal, and cDepartment of Chemistry, University of Aveiro, QOPNA, 3810-193 Aveiro, Portugal
*Correspondence e-mail: filipe.paz@ua.pt
The 3H4N4O2·0.5H2O, comprises two whole molecules of 5-amino-1H-1,2,4-triazole-3-carboxylic acid in its zwitterionic form (proton transfer occurs from the carboxylic acid group to the N heteroatom at position 1), plus one water molecule of crystallization. The organic moieties are disposed into supramolecular layers linked by N—H⋯O and N—H⋯N hydrogen bonds parallel to the bc plane. Additional O—H⋯O and N—H⋯O hydrogen bonds involving the water molecules and the organic molecules lead to the formation of double-deck supramolecular arrangements which are interconnected along the a axis via π–π stacking [centroid–centroid distance = 3.507 (3) Å].
of the title compound, CRelated literature
For related compounds with 5-amino-1H-1,2,4-triazole-3-carboxylic acid residues, see: Masiukiewicz et al. (2007); Ouakkaf et al. (2011); Sun et al. (2011); Wawrzycka-Gorczyca et al. (2003). For previous work in crystal engineering, see: Amarante, Gonçalves et al. (2009); Amarante, Figueiredo et al. (2009); Shi et al. (2008); Paz & Klinowski (2004, 2007); Paz et al. (2005). For graph-set notation, see: Grell et al. (1999). For a description of the Cambridge Structural Database, see: Allen (2002).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2006); cell SAINT-Plus (Bruker, 2005); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: SHELXTL.
Supporting information
10.1107/S160053681102811X/tk2764sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S160053681102811X/tk2764Isup2.hkl
Supporting information file. DOI: 10.1107/S160053681102811X/tk2764Isup3.cml
5-Amino-1H-1,2,4-triazole-3-carboxylic acid (H2Atrc) and MnSO4 were purchased from Sigma-Aldrich and they were used as received without purification.
H2Atrc (0.1 mmol, 12.8 mg) was dissolved in ca 15 ml of hot water (ca 358 K). The solution was then cooled to ambient temperature. A second aqueous solution of MnSO4 (0.1 mmol, 11.7 mg in ca 2 ml) was added drop wise to that containing the dissolved H2Atrc ligand. The resulting mixture solution was allowed to stand still over a period of one week and small colourless blocks were formed as a secondary product.
All hydrogen atoms bound to nitrogen (organic molecules) and to oxygen (water molecule of crystallization) were directly located from difference Fourier maps and included in the structural model with the O—H and N—H distances restrained to 0.95 (1) Å. The H···H distances in the water molecule and in the —NH2 groups were further restrained to 1.55 (1) Å in order to ensure a chemically reasonable geometry for these moieties. The Uiso of these hydrogen atoms were fixed at 1.5×Ueq of the parent nitrogen or oxygen atoms.
Data collection: APEX2 (Bruker, 2006); cell
SAINT-Plus (Bruker, 2005); data reduction: SAINT-Plus (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).Fig. 1. Molecular structures of the units composing the asymmetric unit of the title compound, showing the atomic labelling for all atoms. Non-hydrogen atoms are represented as displacement ellipsoids drawn at the 70% probability level. Hydrogen atoms are depicted as small spheres with arbitrary radii. | |
Fig. 2. N—H···N and N—H···O interactions (dashed green lines) forming the supramolecular layer placed in the bc plane of the unit cell. The two distinct H2Atrc residues are depicted as molecules A and B. Supramolecular arrangements are described by their graph set notation following Grell et al. (1999). For geometric details on the represented supramolecular contacts see Table 1. Symmetry transformations used to generate equivalent atoms have been omitted for clarity. | |
Fig. 3. Crystal packing of the title compound viewed in perspective along the [010] direction of the unit cell. Hydrogen bonding interactions between H2Atrc moieties are depicted as dashed green lines, while those involving the water molecules of crystallization are represented as dashed pink lines. π-π stacking interactions are represented as dashed orange lines. |
C3H4N4O2·0.5H2O | Z = 4 |
Mr = 137.11 | F(000) = 284 |
Triclinic, P1 | Dx = 1.755 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 6.5440 (11) Å | Cell parameters from 2284 reflections |
b = 6.9490 (8) Å | θ = 3.0–26.5° |
c = 12.0723 (17) Å | µ = 0.15 mm−1 |
α = 93.976 (7)° | T = 150 K |
β = 105.012 (9)° | Block, colourless |
γ = 99.703 (8)° | 0.10 × 0.07 × 0.04 mm |
V = 518.96 (13) Å3 |
Bruker X8 KappaCCD APEXII diffractometer | 1797 independent reflections |
Radiation source: fine-focus sealed tube | 1433 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.032 |
ω and ϕ scans | θmax = 25.3°, θmin = 3.7° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1997) | h = −7→7 |
Tmin = 0.985, Tmax = 0.994 | k = −8→8 |
4474 measured reflections | l = −14→14 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.066 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.202 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.24 | w = 1/[σ2(Fo2) + (0.053P)2 + 2.637P] where P = (Fo2 + 2Fc2)/3 |
1797 reflections | (Δ/σ)max < 0.001 |
202 parameters | Δρmax = 0.42 e Å−3 |
13 restraints | Δρmin = −0.46 e Å−3 |
C3H4N4O2·0.5H2O | γ = 99.703 (8)° |
Mr = 137.11 | V = 518.96 (13) Å3 |
Triclinic, P1 | Z = 4 |
a = 6.5440 (11) Å | Mo Kα radiation |
b = 6.9490 (8) Å | µ = 0.15 mm−1 |
c = 12.0723 (17) Å | T = 150 K |
α = 93.976 (7)° | 0.10 × 0.07 × 0.04 mm |
β = 105.012 (9)° |
Bruker X8 KappaCCD APEXII diffractometer | 1797 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1997) | 1433 reflections with I > 2σ(I) |
Tmin = 0.985, Tmax = 0.994 | Rint = 0.032 |
4474 measured reflections |
R[F2 > 2σ(F2)] = 0.066 | 13 restraints |
wR(F2) = 0.202 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.24 | Δρmax = 0.42 e Å−3 |
1797 reflections | Δρmin = −0.46 e Å−3 |
202 parameters |
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 F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.2627 (6) | 0.4287 (5) | 1.1942 (3) | 0.0210 (8) | |
O2 | 0.2494 (6) | 0.6539 (5) | 1.0686 (3) | 0.0204 (8) | |
C1 | 0.2566 (8) | 0.4869 (7) | 1.0970 (4) | 0.0181 (11) | |
C2 | 0.2597 (8) | 0.3319 (7) | 1.0033 (4) | 0.0145 (10) | |
C3 | 0.2551 (8) | 0.2009 (7) | 0.8332 (4) | 0.0151 (10) | |
N1 | 0.2483 (7) | 0.3692 (6) | 0.8926 (3) | 0.0156 (9) | |
H1 | 0.230 (9) | 0.492 (4) | 0.867 (5) | 0.023* | |
N2 | 0.2760 (7) | 0.1506 (6) | 1.0170 (3) | 0.0190 (10) | |
N3 | 0.2736 (7) | 0.0699 (6) | 0.9090 (3) | 0.0180 (9) | |
H3 | 0.262 (9) | −0.066 (2) | 0.887 (5) | 0.027* | |
N4 | 0.2452 (7) | 0.1709 (6) | 0.7223 (3) | 0.0185 (10) | |
H4A | 0.234 (9) | 0.266 (5) | 0.670 (3) | 0.028* | |
H4B | 0.251 (9) | 0.049 (3) | 0.685 (3) | 0.028* | |
O3 | 0.2553 (6) | 0.3765 (5) | 0.4390 (3) | 0.0227 (9) | |
O4 | 0.2348 (6) | 0.5057 (5) | 0.6096 (3) | 0.0219 (9) | |
C4 | 0.2476 (8) | 0.5132 (7) | 0.5087 (4) | 0.0151 (10) | |
C5 | 0.2534 (8) | 0.7084 (7) | 0.4618 (4) | 0.0146 (10) | |
C6 | 0.2720 (8) | 0.9152 (7) | 0.3368 (4) | 0.0146 (10) | |
N5 | 0.2730 (7) | 0.7267 (6) | 0.3525 (3) | 0.0149 (9) | |
H5 | 0.272 (9) | 0.622 (5) | 0.298 (4) | 0.022* | |
N6 | 0.2409 (7) | 0.8740 (6) | 0.5147 (3) | 0.0167 (9) | |
N7 | 0.2527 (7) | 1.0044 (6) | 0.4344 (3) | 0.0157 (9) | |
H7 | 0.248 (9) | 1.139 (3) | 0.452 (5) | 0.024* | |
N8 | 0.2862 (8) | 0.9965 (6) | 0.2414 (4) | 0.0232 (10) | |
H8A | 0.274 (10) | 0.918 (6) | 0.172 (2) | 0.035* | |
H8B | 0.276 (10) | 1.127 (3) | 0.228 (4) | 0.035* | |
O1W | 0.1593 (6) | 0.7013 (5) | 0.7849 (3) | 0.0225 (9) | |
H1X | 0.009 (2) | 0.672 (8) | 0.775 (4) | 0.034* | |
H1Y | 0.194 (7) | 0.645 (8) | 0.720 (3) | 0.034* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.036 (2) | 0.0223 (19) | 0.0072 (17) | 0.0083 (16) | 0.0077 (15) | 0.0024 (14) |
O2 | 0.030 (2) | 0.0150 (18) | 0.0164 (18) | 0.0058 (15) | 0.0074 (16) | 0.0005 (14) |
C1 | 0.016 (3) | 0.018 (3) | 0.020 (3) | 0.004 (2) | 0.005 (2) | −0.002 (2) |
C2 | 0.018 (3) | 0.016 (2) | 0.010 (2) | 0.004 (2) | 0.0032 (19) | 0.0037 (19) |
C3 | 0.016 (3) | 0.014 (2) | 0.014 (2) | 0.004 (2) | 0.002 (2) | 0.0019 (19) |
N1 | 0.023 (2) | 0.0101 (19) | 0.015 (2) | 0.0050 (17) | 0.0064 (17) | 0.0020 (16) |
N2 | 0.029 (2) | 0.019 (2) | 0.009 (2) | 0.0048 (19) | 0.0049 (18) | 0.0018 (17) |
N3 | 0.030 (2) | 0.013 (2) | 0.012 (2) | 0.0046 (18) | 0.0065 (18) | 0.0002 (17) |
N4 | 0.035 (3) | 0.015 (2) | 0.009 (2) | 0.0097 (19) | 0.0079 (19) | 0.0047 (17) |
O3 | 0.040 (2) | 0.0126 (17) | 0.0193 (19) | 0.0071 (16) | 0.0121 (17) | 0.0045 (15) |
O4 | 0.037 (2) | 0.0174 (18) | 0.0149 (19) | 0.0090 (16) | 0.0099 (16) | 0.0077 (14) |
C4 | 0.022 (3) | 0.013 (2) | 0.011 (3) | 0.005 (2) | 0.005 (2) | 0.0067 (19) |
C5 | 0.018 (3) | 0.014 (2) | 0.012 (2) | 0.004 (2) | 0.006 (2) | 0.0017 (19) |
C6 | 0.018 (2) | 0.013 (2) | 0.014 (2) | 0.005 (2) | 0.004 (2) | 0.0044 (19) |
N5 | 0.025 (2) | 0.011 (2) | 0.011 (2) | 0.0052 (17) | 0.0065 (17) | 0.0043 (16) |
N6 | 0.023 (2) | 0.015 (2) | 0.013 (2) | 0.0035 (17) | 0.0045 (18) | 0.0066 (17) |
N7 | 0.024 (2) | 0.0088 (19) | 0.015 (2) | 0.0058 (17) | 0.0059 (18) | 0.0024 (16) |
N8 | 0.038 (3) | 0.018 (2) | 0.017 (2) | 0.009 (2) | 0.011 (2) | 0.0064 (18) |
O1W | 0.033 (2) | 0.0174 (18) | 0.0194 (19) | 0.0064 (16) | 0.0098 (16) | −0.0001 (15) |
O1—C1 | 1.260 (6) | O4—C4 | 1.246 (6) |
O2—C1 | 1.238 (6) | C4—C5 | 1.504 (6) |
C1—C2 | 1.513 (7) | C5—N6 | 1.302 (6) |
C2—N2 | 1.300 (6) | C5—N5 | 1.370 (6) |
C2—N1 | 1.364 (6) | C6—N8 | 1.335 (6) |
C3—N4 | 1.324 (6) | C6—N5 | 1.337 (6) |
C3—N3 | 1.332 (6) | C6—N7 | 1.339 (6) |
C3—N1 | 1.343 (6) | N5—H5 | 0.947 (10) |
N1—H1 | 0.946 (11) | N6—N7 | 1.380 (5) |
N2—N3 | 1.378 (6) | N7—H7 | 0.948 (10) |
N3—H3 | 0.947 (11) | N8—H8A | 0.944 (10) |
N4—H4A | 0.943 (10) | N8—H8B | 0.944 (10) |
N4—H4B | 0.944 (10) | O1W—H1X | 0.946 (10) |
O3—C4 | 1.241 (6) | O1W—H1Y | 0.945 (10) |
O2—C1—O1 | 128.4 (4) | O3—C4—C5 | 114.0 (4) |
O2—C1—C2 | 116.0 (4) | O4—C4—C5 | 118.2 (4) |
O1—C1—C2 | 115.5 (4) | N6—C5—N5 | 112.4 (4) |
N2—C2—N1 | 111.7 (4) | N6—C5—C4 | 126.8 (4) |
N2—C2—C1 | 125.4 (4) | N5—C5—C4 | 120.8 (4) |
N1—C2—C1 | 122.9 (4) | N8—C6—N5 | 126.1 (4) |
N4—C3—N3 | 127.0 (5) | N8—C6—N7 | 127.1 (4) |
N4—C3—N1 | 127.2 (4) | N5—C6—N7 | 106.7 (4) |
N3—C3—N1 | 105.8 (4) | C6—N5—C5 | 106.3 (4) |
C3—N1—C2 | 107.2 (4) | C6—N5—H5 | 128 (3) |
C3—N1—H1 | 130 (3) | C5—N5—H5 | 126 (3) |
C2—N1—H1 | 123 (3) | C5—N6—N7 | 103.5 (4) |
C2—N2—N3 | 103.7 (4) | C6—N7—N6 | 111.1 (4) |
C3—N3—N2 | 111.6 (4) | C6—N7—H7 | 128 (3) |
C3—N3—H3 | 123 (3) | N6—N7—H7 | 121 (3) |
N2—N3—H3 | 125 (3) | C6—N8—H8A | 121 (3) |
C3—N4—H4A | 126 (3) | C6—N8—H8B | 127 (3) |
C3—N4—H4B | 123 (3) | H8A—N8—H8B | 111 (4) |
H4A—N4—H4B | 110.9 (16) | H1X—O1W—H1Y | 111 (4) |
O3—C4—O4 | 127.8 (4) | ||
O2—C1—C2—N2 | 177.0 (5) | O3—C4—C5—N6 | 177.7 (5) |
O1—C1—C2—N2 | −2.7 (7) | O4—C4—C5—N6 | −1.9 (8) |
O2—C1—C2—N1 | −2.0 (7) | O3—C4—C5—N5 | −2.0 (7) |
O1—C1—C2—N1 | 178.2 (5) | O4—C4—C5—N5 | 178.3 (5) |
N4—C3—N1—C2 | 179.0 (5) | N8—C6—N5—C5 | −179.5 (5) |
N3—C3—N1—C2 | −1.0 (5) | N7—C6—N5—C5 | 0.1 (5) |
N2—C2—N1—C3 | 0.8 (6) | N6—C5—N5—C6 | −0.1 (6) |
C1—C2—N1—C3 | 180.0 (4) | C4—C5—N5—C6 | 179.7 (4) |
N1—C2—N2—N3 | −0.3 (6) | N5—C5—N6—N7 | 0.1 (5) |
C1—C2—N2—N3 | −179.5 (5) | C4—C5—N6—N7 | −179.7 (5) |
N4—C3—N3—N2 | −179.1 (5) | N8—C6—N7—N6 | 179.6 (5) |
N1—C3—N3—N2 | 0.8 (6) | N5—C6—N7—N6 | 0.0 (5) |
C2—N2—N3—C3 | −0.3 (6) | C5—N6—N7—C6 | −0.1 (5) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1W | 0.95 (1) | 1.87 (2) | 2.799 (5) | 167 (5) |
N3—H3···O1Wi | 0.95 (1) | 1.87 (3) | 2.758 (5) | 154 (5) |
N4—H4A···O4 | 0.94 (1) | 1.86 (2) | 2.777 (5) | 163 (4) |
N4—H4B···N6i | 0.94 (1) | 2.29 (3) | 3.125 (6) | 146 (4) |
N5—H5···O1ii | 0.95 (1) | 1.75 (1) | 2.699 (5) | 178 (5) |
N7—H7···O3iii | 0.95 (1) | 1.66 (2) | 2.579 (5) | 161 (5) |
N8—H8A···O2ii | 0.94 (1) | 2.10 (2) | 2.989 (5) | 155 (4) |
N8—H8B···O1iv | 0.94 (1) | 2.17 (1) | 3.117 (5) | 178 (5) |
O1W—H1X···O1v | 0.95 (1) | 1.94 (2) | 2.839 (5) | 159 (5) |
O1W—H1Y···O4 | 0.95 (1) | 1.70 (2) | 2.634 (5) | 170 (5) |
Symmetry codes: (i) x, y−1, z; (ii) x, y, z−1; (iii) x, y+1, z; (iv) x, y+1, z−1; (v) −x, −y+1, −z+2. |
Experimental details
Crystal data | |
Chemical formula | C3H4N4O2·0.5H2O |
Mr | 137.11 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 150 |
a, b, c (Å) | 6.5440 (11), 6.9490 (8), 12.0723 (17) |
α, β, γ (°) | 93.976 (7), 105.012 (9), 99.703 (8) |
V (Å3) | 518.96 (13) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.15 |
Crystal size (mm) | 0.10 × 0.07 × 0.04 |
Data collection | |
Diffractometer | Bruker X8 KappaCCD APEXII diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1997) |
Tmin, Tmax | 0.985, 0.994 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4474, 1797, 1433 |
Rint | 0.032 |
(sin θ/λ)max (Å−1) | 0.602 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.066, 0.202, 1.24 |
No. of reflections | 1797 |
No. of parameters | 202 |
No. of restraints | 13 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.42, −0.46 |
Computer programs: APEX2 (Bruker, 2006), SAINT-Plus (Bruker, 2005), SHELXTL (Sheldrick, 2008), DIAMOND (Brandenburg, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1W | 0.946 (11) | 1.868 (17) | 2.799 (5) | 167 (5) |
N3—H3···O1Wi | 0.947 (11) | 1.87 (3) | 2.758 (5) | 154 (5) |
N4—H4A···O4 | 0.943 (10) | 1.863 (16) | 2.777 (5) | 163 (4) |
N4—H4B···N6i | 0.944 (10) | 2.29 (3) | 3.125 (6) | 146 (4) |
N5—H5···O1ii | 0.947 (10) | 1.752 (12) | 2.699 (5) | 178 (5) |
N7—H7···O3iii | 0.948 (10) | 1.66 (2) | 2.579 (5) | 161 (5) |
N8—H8A···O2ii | 0.944 (10) | 2.10 (2) | 2.989 (5) | 155 (4) |
N8—H8B···O1iv | 0.944 (10) | 2.173 (12) | 3.117 (5) | 178 (5) |
O1W—H1X···O1v | 0.946 (10) | 1.94 (2) | 2.839 (5) | 159 (5) |
O1W—H1Y···O4 | 0.945 (10) | 1.699 (16) | 2.634 (5) | 170 (5) |
Symmetry codes: (i) x, y−1, z; (ii) x, y, z−1; (iii) x, y+1, z; (iv) x, y+1, z−1; (v) −x, −y+1, −z+2. |
Acknowledgements
We are grateful to the Fundação para a Ciência e a Tecnologia (FCT, Portugal) for their general financial support under the R&D projects PTDC/QUI-QUI/098098/2008 and PTDC/CTM/100357/2008, and for the post-doctoral research grants, Nos. SFRH/BPD/63736/2009 (to JAF) and SFRH/BPD/47566/2008 (to BL). Thanks are also due to FCT for specific funding toward the purchase of the single-crystal diffractometer.
References
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5-Amino-1H-1,2,4-triazole-3-carboxylic acid (H2Atrc) arises as a promising ligand which can be employed in the preparation of coordination compounds as a consequence of its multiple available sites to establish direct connections with metallic centres. However, surveying the Cambridge Structural Database (Allen, 2002) showed only a handful of crystalline compounds reported to date, namely organic derivatives (Masiukiewicz et al., 2007; Wawrzycka-Gorczyca et al., 2003), the sulfate salt (Ouakkaf et al., 2011) and a three-dimensional metal-organic framework (MOF) with Dy3+, very recently reported by Sun et al. (2011). Following our on-going interest on crystal engineering approaches of both organic crystals (Amarante, Gonçalves et al., 2009; Amarante, Figueiredo et al., 2009) and metal-organic frameworks (Shi et al., 2008; Paz & Klinowski, 2007; Paz et al., 2005; Paz & Klinowski, 2004), we are currently interested in exploring the coordination capabilities of H2Atrc and its residues. The title compound was isolated as a secondary minor product for which we wish to report its crystal structure at the low temperature of 150 K.
The asymmetric unit of title compound comprises two whole molecules of H2Atrc in its zwitterionic form (proton transference occurs from the carboxylic acid group to the N heteroatom at position 1) and a water molecule of crystallization as depicted in Fig. 1. The two individual molecular units are almost planar, with the observed deviations being smaller than 0.037 Å. The two organic moieties are also mutually located in the same average plane, with the average planes subtending an angle of ca 7.2 °. This planarity is extended throughout the entire crystal structure with the organic moieties being disposed in layers placed in the bc plane of the unit cell.
Due to the presence of a considerable number of proton donors and acceptors, the crystal structure is rich in hydrogen bonding interactions (see Table 1 for further details). In this context, the structural function of the two non-equivalent organic molecules composing the asymmetric unit is not the same since the hydrogen bonding interactions in which each moiety is involved differ considerably. While the moiety coined as A interacts with other symmetry-related moieties and also with B, the residue coined as B only interacts with A and with water molecules of crystallization. Given the coplanarity of the two non-equivalent H2Atrc molecules, mutual interactions occur solely along the aforementioned layers, forming several fused hydrogen-bonded rings (green dashed lines in Figs 2 and 3), best described by the graph set motifs R22(8), R33(9) and R32(11) (Grell et al., 1999). Because of the hydrogen bonds directly involving the crystallographically independent water molecule of crystallization (pink dashed lines in Fig. 3), individual moieties are arranged into double decker layers as depicted in Fig. 3. These supramolecular arrays interact between each other along the a-axis of the unit cell via weak interactions such as π-π stacking. The most structurally relevant of such interactions occurs between two symmetry-equivalent A moieties with an inter-centroid distance of 3.507 (3) Å (orange dashed lines in Figure 3).