Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807034356/wn2170sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536807034356/wn2170Isup2.hkl |
CCDC reference: 659089
Key indicators
- Single-crystal X-ray study
- T = 297 K
- Mean (C-C) = 0.003 Å
- R factor = 0.047
- wR factor = 0.147
- Data-to-parameter ratio = 13.2
checkCIF/PLATON results
No syntax errors found
Alert level C PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ .... ? PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical . ? PLAT369_ALERT_2_C Long C(sp2)-C(sp2) Bond C2 - C21 ... 1.53 Ang. PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd. # 3 H2 O
0 ALERT level A = In general: serious problem 0 ALERT level B = Potentially serious problem 4 ALERT level C = Check and explain 0 ALERT level G = General alerts; check 2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 1 ALERT type 2 Indicator that the structure model may be wrong or deficient 0 ALERT type 3 Indicator that the structure quality may be low 1 ALERT type 4 Improvement, methodology, query or suggestion 0 ALERT type 5 Informative message, check
For related literature, see: Bernstein et al. (1995); Glidewell et al. (2003, 2005); Guo (2004); Smith et al. (2001, 2005); Smith, Wermuth & White (2007); Smith, Wermuth, Healy & White (2007).
The title compound was synthesized by heating together 1 mmol quantities of 3-nitrophthalic acid and guanidine carbonate in 50 ml of methanol under reflux for 10 minutes. After concentration to ca 30 ml, partial room temperature evaporation of the hot-filtered solution gave colourless crystal prisms (m.p. 395–396 K).
Hydrogen atoms involved in hydrogen-bonding interactions were located by difference methods and their positional and isotropic displacement parameters were refined. The ranges of refined bond lengths were N—H = 0.83 (3)–0.91 (4) Å and O—H = 0.85 (5)–0.89 (4) Å. The aromatic H atoms were included in the refinement in calculated positions (C—H = 0.95 Å) using a riding model approximation, with Uiso(H) = 1.2Ueq(C).
The structures of the guanidinium salts of nitro-substituted benzoic acids are not numerous in the crystallographic literature. Among these are the 1:1 anhydrous guanidinium salts of 3,5-dinitrosalicylic acid (Smith et al., 2001), 3,5-dinitrobenzoic acid (Smith, Wermuth & White, 2007) and 4-nitroanthranilic acid (a monohydrate) (Smith et al., 2007). The nitro-substituted aromatic dicarboxylic acids provide additional potential for structure extension and some structures of 1:1 Lewis base salts of these acids are known, e.g. the anhydrous compounds of 3-nitrophthalic acid with 3-iodoaniline (Glidewell et al.. 2005) and 4-iodoaniline (Glidewell et al.. 2003 and the dihydrate with brucine (Smith et al., 2005). In the 1:1 dihydrate salt with piperazine (Guo, 2004), the phthalate species is dianionic.
Our 1:1 stoichiometric reaction of 3-nitrophthalic acid with guanidinium carbonate in methanol surprisingly gave good crystals of a hydrated salt guanidinium 2-carboxy-6-nitrobenzoate monohydrate, CH6N3+.C8H4NO6-.H2O, which is reported here. In the title compound, the usual proton transfer occurs from the central (C2) carboxylic acid group which is then involved in a direct hydrogen-bonding interaction with a guanidinium proton (Fig. 1). The guanidinium protons are involved in eight hydrogen bonds with all but one of the available O acceptors (nitro O31B) (Table 1). These include the water molecule of solvation which also provides a bridging link between the two separate carboxylate O-acceptors (O21Ai, O21B: symmetry code (i), x, y, z + 1], extending the structure down the c cell direction. With the guanidinium cation there is an asymmetric cyclic R21(6) (Bernstein et al., 1995) interaction also with a carboxylate O-acceptor together with a conjoint R12(7) nitro-O interaction. The carboxylic acid proton gives a strong hydrogen bond with the water molecule [O···O, 2.528 (2) Å], the overall result being a two-dimensional network structure (Fig. 2).
Within the 3-nitrophthalate anion, the carboxylate group is close to perpendicular to the plane of the benzene ring [C1—C2—C21—O21A, 101.2 (2)°], while the carboxylic acid group is close to coplanar [C2—C1—C11—O11A, 173.34 (19)°]. The nitro group is intermediate between these [C2—3—N31—O31B, 151.2 (2) °]. This conformation is similar to that found in other acid salts of 3-nitrophthalic acid (Smith et al., 2005; Glidewell et al. 2003, 2005). In addition there is an intramolecular aromatic ring hydrogen bond [C6–H···O11A: 2.706 (3) Å] associated with the carboxylic acid group.
For related literature, see: Bernstein et al. (1995); Glidewell et al. (2003, 2005); Guo (2004); Smith et al. (2001, 2005); Smith, Wermuth & White (2007); Smith, Wermuth, Healy & White (2007).
Data collection: MSC/AFC Diffractmeter Control Software (Molecular Structure Corporation, 1999); cell refinement: MSC/AFC Diffractmeter Control Software; data reduction: TEXSAN for Windows (Molecular Structure Corporation, 1999); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: PLATON.
CH6N3+·C8H4NO6−·H2O | F(000) = 600 |
Mr = 288.23 | Dx = 1.528 Mg m−3 |
Monoclinic, P21/c | Melting point = 395–396 K |
Hall symbol: -P 2ybc | Mo Kα radiation, λ = 0.71073 Å |
a = 14.758 (3) Å | Cell parameters from 25 reflections |
b = 12.5955 (19) Å | θ = 12.6–17.5° |
c = 6.8423 (12) Å | µ = 0.13 mm−1 |
β = 100.006 (16)° | T = 297 K |
V = 1252.5 (4) Å3 | Cut block, colourless |
Z = 4 | 0.40 × 0.35 × 0.20 mm |
Rigaku AFC-7R diffractometer | 2080 reflections with I > 2σ(I) |
Radiation source: rotating anode | Rint = 0.028 |
Graphite monochromator | θmax = 27.5°, θmin = 2.8° |
ω/2θ scans | h = −18→19 |
Absorption correction: ψ scan (TEXSAN for Windows; Molecular Structure Corporation, 1999) | k = 0→16 |
Tmin = 0.949, Tmax = 0.974 | l = −8→3 |
3307 measured reflections | 3 standard reflections every 150 min |
2872 independent reflections | intensity decay: 1.2% |
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)] = 0.047 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.147 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.86 | w = 1/[σ2(Fo2) + (0.1P)2 + 5.5554P] where P = (Fo2 + 2Fc2)/3 |
2872 reflections | (Δ/σ)max = 0.001 |
217 parameters | Δρmax = 0.33 e Å−3 |
0 restraints | Δρmin = −0.40 e Å−3 |
CH6N3+·C8H4NO6−·H2O | V = 1252.5 (4) Å3 |
Mr = 288.23 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 14.758 (3) Å | µ = 0.13 mm−1 |
b = 12.5955 (19) Å | T = 297 K |
c = 6.8423 (12) Å | 0.40 × 0.35 × 0.20 mm |
β = 100.006 (16)° |
Rigaku AFC-7R diffractometer | 2080 reflections with I > 2σ(I) |
Absorption correction: ψ scan (TEXSAN for Windows; Molecular Structure Corporation, 1999) | Rint = 0.028 |
Tmin = 0.949, Tmax = 0.974 | 3 standard reflections every 150 min |
3307 measured reflections | intensity decay: 1.2% |
2872 independent reflections |
R[F2 > 2σ(F2)] = 0.047 | 0 restraints |
wR(F2) = 0.147 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.86 | Δρmax = 0.33 e Å−3 |
2872 reflections | Δρmin = −0.40 e Å−3 |
217 parameters |
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles |
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 | ||
O11A | 0.33502 (12) | 1.28306 (13) | 0.6829 (3) | 0.0402 (6) | |
O11B | 0.21101 (11) | 1.19235 (14) | 0.5452 (3) | 0.0436 (6) | |
O21A | 0.16688 (11) | 0.96584 (13) | 0.4120 (2) | 0.0331 (5) | |
O21B | 0.16155 (10) | 0.98708 (14) | 0.7330 (2) | 0.0339 (5) | |
O31A | 0.25485 (12) | 0.78120 (15) | 0.6336 (3) | 0.0480 (6) | |
O31B | 0.38515 (13) | 0.73913 (16) | 0.5523 (3) | 0.0551 (7) | |
N31 | 0.33335 (13) | 0.80279 (15) | 0.6115 (3) | 0.0338 (6) | |
C1 | 0.34791 (14) | 1.09732 (17) | 0.6688 (3) | 0.0266 (6) | |
C2 | 0.30745 (13) | 0.99645 (16) | 0.6370 (3) | 0.0240 (5) | |
C3 | 0.36807 (14) | 0.91080 (17) | 0.6560 (3) | 0.0270 (6) | |
C4 | 0.46275 (15) | 0.92106 (19) | 0.7140 (4) | 0.0337 (7) | |
C5 | 0.50006 (15) | 1.0204 (2) | 0.7553 (4) | 0.0374 (7) | |
C6 | 0.44276 (15) | 1.10785 (19) | 0.7288 (4) | 0.0346 (7) | |
C11 | 0.29065 (15) | 1.19500 (17) | 0.6278 (3) | 0.0283 (6) | |
C21 | 0.20296 (13) | 0.98198 (16) | 0.5881 (3) | 0.0250 (6) | |
N12 | 0.08940 (15) | 0.7473 (2) | 0.8170 (3) | 0.0406 (7) | |
N22 | −0.05841 (16) | 0.6993 (2) | 0.6799 (4) | 0.0454 (7) | |
N32 | −0.01159 (16) | 0.87191 (19) | 0.6668 (4) | 0.0409 (7) | |
C12 | 0.00621 (15) | 0.77276 (19) | 0.7218 (3) | 0.0313 (6) | |
O1W | 0.25121 (17) | 1.04247 (17) | 1.1102 (4) | 0.0536 (7) | |
H4 | 0.50130 | 0.86020 | 0.72510 | 0.0400* | |
H5 | 0.56420 | 1.02870 | 0.80120 | 0.0450* | |
H6 | 0.46850 | 1.17680 | 0.75190 | 0.0420* | |
H11A | 0.299 (3) | 1.340 (3) | 0.655 (5) | 0.069 (11)* | |
H12A | 0.104 (2) | 0.678 (3) | 0.838 (5) | 0.055 (9)* | |
H12B | 0.130 (2) | 0.796 (3) | 0.839 (5) | 0.056 (10)* | |
H22A | −0.113 (3) | 0.720 (3) | 0.605 (6) | 0.071 (11)* | |
H22B | −0.050 (2) | 0.637 (3) | 0.733 (5) | 0.056 (9)* | |
H32A | 0.030 (2) | 0.917 (3) | 0.683 (5) | 0.058 (10)* | |
H32B | −0.066 (3) | 0.894 (3) | 0.629 (5) | 0.063 (10)* | |
H1W | 0.222 (3) | 1.022 (3) | 0.994 (7) | 0.071 (12)* | |
H2W | 0.221 (3) | 1.018 (3) | 1.196 (7) | 0.078 (13)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O11A | 0.0312 (9) | 0.0252 (8) | 0.0599 (12) | 0.0003 (7) | −0.0037 (8) | −0.0040 (8) |
O11B | 0.0257 (8) | 0.0321 (9) | 0.0679 (12) | 0.0020 (7) | −0.0064 (8) | 0.0011 (8) |
O21A | 0.0271 (8) | 0.0384 (9) | 0.0304 (8) | −0.0047 (7) | −0.0042 (6) | −0.0010 (7) |
O21B | 0.0254 (8) | 0.0420 (9) | 0.0352 (9) | −0.0050 (7) | 0.0077 (6) | −0.0025 (7) |
O31A | 0.0332 (9) | 0.0341 (9) | 0.0750 (14) | −0.0063 (7) | 0.0045 (9) | −0.0017 (9) |
O31B | 0.0406 (10) | 0.0408 (10) | 0.0789 (15) | 0.0122 (8) | −0.0036 (10) | −0.0200 (10) |
N31 | 0.0288 (9) | 0.0273 (9) | 0.0407 (11) | 0.0034 (8) | −0.0069 (8) | −0.0018 (8) |
C1 | 0.0206 (9) | 0.0274 (10) | 0.0309 (11) | 0.0001 (8) | 0.0019 (8) | 0.0003 (8) |
C2 | 0.0200 (9) | 0.0279 (10) | 0.0232 (9) | −0.0004 (7) | 0.0015 (7) | −0.0008 (8) |
C3 | 0.0232 (10) | 0.0267 (10) | 0.0294 (10) | 0.0007 (8) | −0.0004 (8) | −0.0009 (8) |
C4 | 0.0218 (10) | 0.0343 (12) | 0.0427 (13) | 0.0058 (9) | −0.0008 (9) | 0.0025 (10) |
C5 | 0.0187 (9) | 0.0401 (13) | 0.0510 (14) | 0.0000 (9) | −0.0008 (9) | 0.0020 (11) |
C6 | 0.0246 (10) | 0.0307 (11) | 0.0462 (13) | −0.0047 (9) | −0.0004 (9) | 0.0000 (10) |
C11 | 0.0269 (10) | 0.0262 (10) | 0.0316 (11) | −0.0008 (8) | 0.0045 (8) | −0.0002 (8) |
C21 | 0.0200 (9) | 0.0217 (9) | 0.0321 (11) | 0.0003 (7) | 0.0011 (8) | 0.0004 (8) |
N12 | 0.0273 (10) | 0.0456 (13) | 0.0464 (12) | 0.0044 (10) | −0.0008 (9) | 0.0084 (10) |
N22 | 0.0350 (11) | 0.0429 (13) | 0.0551 (14) | −0.0070 (10) | −0.0011 (10) | 0.0137 (11) |
N32 | 0.0274 (10) | 0.0376 (12) | 0.0559 (14) | 0.0050 (9) | 0.0026 (9) | 0.0080 (10) |
C12 | 0.0251 (10) | 0.0376 (12) | 0.0312 (11) | 0.0023 (9) | 0.0047 (8) | 0.0055 (9) |
O1W | 0.0732 (15) | 0.0483 (12) | 0.0396 (11) | −0.0297 (11) | 0.0107 (11) | −0.0049 (9) |
O11A—C11 | 1.310 (3) | N22—H22B | 0.87 (4) |
O11B—C11 | 1.213 (3) | N22—H22A | 0.91 (4) |
O21A—C21 | 1.247 (2) | N32—H32B | 0.85 (4) |
O21B—C21 | 1.253 (2) | N32—H32A | 0.83 (3) |
O31A—N31 | 1.225 (3) | C1—C6 | 1.395 (3) |
O31B—N31 | 1.224 (3) | C1—C11 | 1.491 (3) |
O11A—H11A | 0.89 (4) | C1—C2 | 1.405 (3) |
O1W—H1W | 0.88 (5) | C2—C3 | 1.393 (3) |
O1W—H2W | 0.85 (5) | C2—C21 | 1.531 (3) |
N31—C3 | 1.467 (3) | C3—C4 | 1.391 (3) |
N12—C12 | 1.325 (3) | C4—C5 | 1.376 (3) |
N22—C12 | 1.324 (3) | C5—C6 | 1.381 (3) |
N32—C12 | 1.318 (3) | C4—H4 | 0.9500 |
N12—H12B | 0.85 (4) | C5—H5 | 0.9500 |
N12—H12A | 0.91 (4) | C6—H6 | 0.9500 |
C11—O11A—H11A | 112 (3) | N31—C3—C4 | 116.29 (19) |
H1W—O1W—H2W | 107 (4) | N31—C3—C2 | 120.22 (18) |
O31A—N31—C3 | 118.95 (19) | C3—C4—C5 | 119.3 (2) |
O31A—N31—O31B | 123.6 (2) | C4—C5—C6 | 119.0 (2) |
O31B—N31—C3 | 117.41 (19) | C1—C6—C5 | 121.5 (2) |
C12—N12—H12B | 118 (2) | O11A—C11—O11B | 123.6 (2) |
C12—N12—H12A | 119 (2) | O11A—C11—C1 | 113.95 (19) |
H12A—N12—H12B | 122 (3) | O11B—C11—C1 | 122.4 (2) |
H22A—N22—H22B | 123 (3) | O21A—C21—C2 | 118.40 (18) |
C12—N22—H22A | 117 (2) | O21B—C21—C2 | 115.60 (17) |
C12—N22—H22B | 120 (2) | O21A—C21—O21B | 126.01 (19) |
H32A—N32—H32B | 117 (3) | C3—C4—H4 | 120.00 |
C12—N32—H32B | 122 (3) | C5—C4—H4 | 120.00 |
C12—N32—H32A | 120 (2) | C6—C5—H5 | 121.00 |
C2—C1—C6 | 120.6 (2) | C4—C5—H5 | 121.00 |
C6—C1—C11 | 118.9 (2) | C5—C6—H6 | 119.00 |
C2—C1—C11 | 120.35 (19) | C1—C6—H6 | 119.00 |
C3—C2—C21 | 122.30 (18) | N12—C12—N22 | 120.6 (2) |
C1—C2—C3 | 115.93 (18) | N12—C12—N32 | 119.4 (2) |
C1—C2—C21 | 121.77 (18) | N22—C12—N32 | 120.0 (2) |
C2—C3—C4 | 123.5 (2) | ||
O31A—N31—C3—C2 | −28.2 (3) | C6—C1—C11—O11B | 167.8 (2) |
O31A—N31—C3—C4 | 152.5 (2) | C1—C2—C3—N31 | −175.49 (18) |
O31B—N31—C3—C2 | 151.2 (2) | C1—C2—C3—C4 | 3.7 (3) |
O31B—N31—C3—C4 | −28.0 (3) | C21—C2—C3—N31 | 5.6 (3) |
C6—C1—C2—C3 | −4.2 (3) | C21—C2—C3—C4 | −175.3 (2) |
C6—C1—C2—C21 | 174.8 (2) | C1—C2—C21—O21A | 101.2 (2) |
C11—C1—C2—C3 | 172.36 (18) | C1—C2—C21—O21B | −79.2 (3) |
C11—C1—C2—C21 | −8.7 (3) | C3—C2—C21—O21A | −79.9 (3) |
C2—C1—C6—C5 | 1.2 (4) | C3—C2—C21—O21B | 99.7 (2) |
C11—C1—C6—C5 | −175.4 (2) | N31—C3—C4—C5 | 179.1 (2) |
C2—C1—C11—O11A | 173.34 (19) | C2—C3—C4—C5 | −0.1 (4) |
C2—C1—C11—O11B | −8.8 (3) | C3—C4—C5—C6 | −3.1 (4) |
C6—C1—C11—O11A | −10.1 (3) | C4—C5—C6—C1 | 2.5 (4) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1W···O21B | 0.88 (5) | 1.90 (5) | 2.777 (3) | 176 (3) |
O1W—H2W···O21Ai | 0.85 (5) | 1.91 (5) | 2.764 (3) | 173 (4) |
O11A—H11A···O1Wii | 0.89 (4) | 1.65 (4) | 2.528 (3) | 169 (4) |
N12—H12A···O21Aiii | 0.91 (4) | 2.06 (4) | 2.946 (3) | 167 (3) |
N12—H12B···O21B | 0.85 (4) | 2.58 (4) | 3.286 (3) | 141 (3) |
N12—H12B···O31A | 0.85 (4) | 2.51 (3) | 2.964 (3) | 114 (3) |
N22—H22A···O11Biv | 0.91 (4) | 1.96 (4) | 2.846 (3) | 162 (3) |
N22—H22B···O21Bv | 0.87 (4) | 2.54 (3) | 3.183 (3) | 132 (3) |
N32—H32A···O21B | 0.83 (3) | 2.11 (3) | 2.905 (3) | 162 (3) |
N32—H32B···O11Biv | 0.85 (4) | 2.51 (4) | 3.152 (3) | 134 (3) |
N32—H32B···O21Aiv | 0.85 (4) | 2.30 (4) | 3.048 (3) | 148 (3) |
C4—H4···O11Avi | 0.9500 | 2.5800 | 3.420 (3) | 148.00 |
C6—H6···O11A | 0.9500 | 2.3600 | 2.706 (3) | 101.00 |
C6—H6···O31Bvii | 0.9500 | 2.4600 | 3.179 (3) | 132.00 |
Symmetry codes: (i) x, y, z+1; (ii) x, −y+5/2, z−1/2; (iii) x, −y+3/2, z+1/2; (iv) −x, −y+2, −z+1; (v) −x, y−1/2, −z+3/2; (vi) −x+1, y−1/2, −z+3/2; (vii) −x+1, y+1/2, −z+3/2. |
Experimental details
Crystal data | |
Chemical formula | CH6N3+·C8H4NO6−·H2O |
Mr | 288.23 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 297 |
a, b, c (Å) | 14.758 (3), 12.5955 (19), 6.8423 (12) |
β (°) | 100.006 (16) |
V (Å3) | 1252.5 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.13 |
Crystal size (mm) | 0.40 × 0.35 × 0.20 |
Data collection | |
Diffractometer | Rigaku AFC-7R |
Absorption correction | ψ scan (TEXSAN for Windows; Molecular Structure Corporation, 1999) |
Tmin, Tmax | 0.949, 0.974 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3307, 2872, 2080 |
Rint | 0.028 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.047, 0.147, 0.86 |
No. of reflections | 2872 |
No. of parameters | 217 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.33, −0.40 |
Computer programs: MSC/AFC Diffractmeter Control Software (Molecular Structure Corporation, 1999), MSC/AFC Diffractmeter Control Software, TEXSAN for Windows (Molecular Structure Corporation, 1999), SIR92 (Altomare et al., 1994), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 2003), PLATON.
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H1W···O21B | 0.88 (5) | 1.90 (5) | 2.777 (3) | 176 (3) |
O1W—H2W···O21Ai | 0.85 (5) | 1.91 (5) | 2.764 (3) | 173 (4) |
O11A—H11A···O1Wii | 0.89 (4) | 1.65 (4) | 2.528 (3) | 169 (4) |
N12—H12A···O21Aiii | 0.91 (4) | 2.06 (4) | 2.946 (3) | 167 (3) |
N12—H12B···O21B | 0.85 (4) | 2.58 (4) | 3.286 (3) | 141 (3) |
N12—H12B···O31A | 0.85 (4) | 2.51 (3) | 2.964 (3) | 114 (3) |
N22—H22A···O11Biv | 0.91 (4) | 1.96 (4) | 2.846 (3) | 162 (3) |
N22—H22B···O21Bv | 0.87 (4) | 2.54 (3) | 3.183 (3) | 132 (3) |
N32—H32A···O21B | 0.83 (3) | 2.11 (3) | 2.905 (3) | 162 (3) |
N32—H32B···O11Biv | 0.85 (4) | 2.51 (4) | 3.152 (3) | 134 (3) |
N32—H32B···O21Aiv | 0.85 (4) | 2.30 (4) | 3.048 (3) | 148 (3) |
Symmetry codes: (i) x, y, z+1; (ii) x, −y+5/2, z−1/2; (iii) x, −y+3/2, z+1/2; (iv) −x, −y+2, −z+1; (v) −x, y−1/2, −z+3/2. |
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The structures of the guanidinium salts of nitro-substituted benzoic acids are not numerous in the crystallographic literature. Among these are the 1:1 anhydrous guanidinium salts of 3,5-dinitrosalicylic acid (Smith et al., 2001), 3,5-dinitrobenzoic acid (Smith, Wermuth & White, 2007) and 4-nitroanthranilic acid (a monohydrate) (Smith et al., 2007). The nitro-substituted aromatic dicarboxylic acids provide additional potential for structure extension and some structures of 1:1 Lewis base salts of these acids are known, e.g. the anhydrous compounds of 3-nitrophthalic acid with 3-iodoaniline (Glidewell et al.. 2005) and 4-iodoaniline (Glidewell et al.. 2003 and the dihydrate with brucine (Smith et al., 2005). In the 1:1 dihydrate salt with piperazine (Guo, 2004), the phthalate species is dianionic.
Our 1:1 stoichiometric reaction of 3-nitrophthalic acid with guanidinium carbonate in methanol surprisingly gave good crystals of a hydrated salt guanidinium 2-carboxy-6-nitrobenzoate monohydrate, CH6N3+.C8H4NO6-.H2O, which is reported here. In the title compound, the usual proton transfer occurs from the central (C2) carboxylic acid group which is then involved in a direct hydrogen-bonding interaction with a guanidinium proton (Fig. 1). The guanidinium protons are involved in eight hydrogen bonds with all but one of the available O acceptors (nitro O31B) (Table 1). These include the water molecule of solvation which also provides a bridging link between the two separate carboxylate O-acceptors (O21Ai, O21B: symmetry code (i), x, y, z + 1], extending the structure down the c cell direction. With the guanidinium cation there is an asymmetric cyclic R21(6) (Bernstein et al., 1995) interaction also with a carboxylate O-acceptor together with a conjoint R12(7) nitro-O interaction. The carboxylic acid proton gives a strong hydrogen bond with the water molecule [O···O, 2.528 (2) Å], the overall result being a two-dimensional network structure (Fig. 2).
Within the 3-nitrophthalate anion, the carboxylate group is close to perpendicular to the plane of the benzene ring [C1—C2—C21—O21A, 101.2 (2)°], while the carboxylic acid group is close to coplanar [C2—C1—C11—O11A, 173.34 (19)°]. The nitro group is intermediate between these [C2—3—N31—O31B, 151.2 (2) °]. This conformation is similar to that found in other acid salts of 3-nitrophthalic acid (Smith et al., 2005; Glidewell et al. 2003, 2005). In addition there is an intramolecular aromatic ring hydrogen bond [C6–H···O11A: 2.706 (3) Å] associated with the carboxylic acid group.