Hydrogen bonding in 2-carboxy­anilinium dihydrogenphosphate

The structure of the title compound, C₇H₈NO₂⁺·H₂PO₄⁻, shows that a single proton transfer occurs. The anions and cations are held together via strong and short O—H...O hydrogen bonds, in addition to N—H...O inter­actions. The three-dimensional complex network of hydrogen bonds ensures the cohesion of the ionic structure.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.037
• wR factor = 0.090
• Data-to-parameter ratio = 19.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.20
PLAT480_ALERT_4_C Long H...A H-Bond Reported H6     ..  O2      ..       2.67 Ang.
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          2
PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd.  #          2
              H2 O4 P

Alert level G
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   5 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   3 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
   3 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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Computing details

Data collection: KappaCCD Server Software (Nonius, 1998); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK; program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: WinGX (Farrugia, 1999).

2-carboxyanilinium dihydrogenphosphate

Crystal data

C7H8O2N^+·H2PO4^−	Z = 2
Mr = 235.13	F(000) = 244
Triclinic, P1	Dx = 1.655 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 4.8541 (8) Å	Cell parameters from 8460 reflections
b = 9.9845 (9) Å	θ = 1.8–30.0°
c = 10.4849 (2) Å	µ = 0.30 mm^−1
α = 108.383 (5)°	T = 293 K
β = 97.816 (8)°	Plate, colorless
γ = 96.071 (6)°	0.2 × 0.15 × 0.1 mm
V = 471.74 (9) Å^3

Data collection

KappaCCD diffractometer	2363 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.044
Graphite monochromator	θmax = 30.0°, θmin = 2.2°
ω – θ scans	h = −6→6
8460 measured reflections	k = −13→14
2713 independent reflections	l = −13→14

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.037	Hydrogen site location: difference Fourier map
wR(F^2) = 0.090	H-atom parameters constrained
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0347P)^2 + 0.2023P] where P = (Fo^2 + 2Fc^2)/3
2713 reflections	(Δ/σ)max < 0.001
140 parameters	Δρmax = 0.27 e Å^−3
0 restraints	Δρmin = −0.42 e Å^−3

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 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
P	−0.21890 (6)	0.29070 (3)	0.42432 (3)	0.01734 (10)
O2	0.0478 (2)	0.34351 (10)	0.38492 (11)	0.0241 (2)
O4	−0.4667 (2)	0.30783 (14)	0.32184 (12)	0.0351 (3)
H04	−0.6116	0.3070	0.3539	0.053*
O3	−0.2390 (2)	0.39149 (10)	0.57181 (11)	0.0287 (2)
H03	−0.1671	0.4734	0.5828	0.043*
O1	−0.2509 (2)	0.13926 (9)	0.42389 (10)	0.0245 (2)
O5	0.2881 (2)	0.17353 (11)	0.62102 (11)	0.0291 (2)
N	−0.1901 (2)	0.02390 (11)	0.64135 (11)	0.0205 (2)
H2N	−0.3551	−0.0312	0.6282	0.031*
H1N	−0.0562	−0.0306	0.6262	0.031*
H3N	−0.1991	0.0733	0.5840	0.031*
C3	−0.1245 (3)	0.12262 (14)	0.78182 (13)	0.0203 (2)
C1	0.2722 (3)	0.26439 (14)	0.72598 (14)	0.0227 (3)
O6	0.4233 (3)	0.39364 (12)	0.76779 (13)	0.0452 (4)
H1	0.5216	0.3997	0.7115	0.068*
C2	0.0885 (3)	0.24111 (14)	0.82238 (13)	0.0215 (3)
C4	−0.2857 (3)	0.09736 (17)	0.87339 (16)	0.0317 (3)
H4	−0.4264	0.0180	0.8456	0.038*
C7	0.1326 (4)	0.33406 (17)	0.95684 (15)	0.0323 (3)
H7	0.2723	0.4139	0.9853	0.039*
C5	−0.2368 (4)	0.1909 (2)	1.00698 (17)	0.0414 (4)
H5	−0.3446	0.1739	1.0687	0.050*
C6	−0.0291 (4)	0.30889 (19)	1.04844 (16)	0.0401 (4)
H6	0.0024	0.3715	1.1379	0.048*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P	0.01568 (16)	0.01562 (16)	0.02183 (17)	0.00169 (11)	0.00684 (12)	0.00664 (12)
O2	0.0196 (5)	0.0218 (4)	0.0326 (5)	0.0016 (4)	0.0124 (4)	0.0089 (4)
O4	0.0223 (5)	0.0561 (7)	0.0374 (6)	0.0157 (5)	0.0102 (4)	0.0250 (6)
O3	0.0374 (6)	0.0183 (4)	0.0291 (5)	−0.0038 (4)	0.0182 (4)	0.0036 (4)
O1	0.0256 (5)	0.0157 (4)	0.0324 (5)	0.0008 (4)	0.0089 (4)	0.0076 (4)
O5	0.0300 (5)	0.0261 (5)	0.0254 (5)	−0.0040 (4)	0.0121 (4)	0.0002 (4)
N	0.0210 (5)	0.0175 (5)	0.0202 (5)	−0.0020 (4)	0.0049 (4)	0.0038 (4)
C3	0.0220 (6)	0.0199 (6)	0.0181 (6)	0.0016 (5)	0.0045 (5)	0.0052 (5)
C1	0.0225 (6)	0.0198 (6)	0.0222 (6)	−0.0026 (5)	0.0036 (5)	0.0039 (5)
O6	0.0590 (8)	0.0272 (6)	0.0376 (7)	−0.0199 (5)	0.0235 (6)	−0.0032 (5)
C2	0.0226 (6)	0.0211 (6)	0.0189 (6)	0.0005 (5)	0.0047 (5)	0.0045 (5)
C4	0.0347 (8)	0.0333 (8)	0.0269 (7)	−0.0042 (6)	0.0105 (6)	0.0108 (6)
C7	0.0375 (8)	0.0288 (7)	0.0222 (7)	−0.0044 (6)	0.0047 (6)	0.0002 (6)
C5	0.0508 (10)	0.0506 (10)	0.0246 (8)	−0.0001 (8)	0.0179 (7)	0.0131 (7)
C6	0.0524 (10)	0.0425 (9)	0.0185 (7)	−0.0006 (8)	0.0095 (7)	0.0016 (6)

Geometric parameters (Å, º)

P—O1	1.502 (1)	C3—C2	1.3977 (18)
P—O2	1.504 (2)	C1—O6	1.323 (1)
P—O4	1.562 (1)	C1—C2	1.4903 (18)
P—O3	1.579 (2)	O6—H1	0.8200
O4—H04	0.8200	C2—C7	1.395 (2)
O3—H03	0.8200	C4—C5	1.389 (2)
O5—C1	1.203 (2)	C4—H4	0.9300
N—C3	1.460 (1)	C7—C6	1.385 (2)
N—H2N	0.8900	C7—H7	0.9300
N—H1N	0.8900	C5—C6	1.378 (3)
N—H3N	0.8900	C5—H5	0.9300
C3—C4	1.3830 (19)	C6—H6	0.9300
O1—P—O2	115.84 (6)	O5—C1—C2	123.48 (12)
O1—P—O4	109.74 (7)	O6—C1—C2	113.87 (12)
O2—P—O4	106.23 (6)	C1—O6—H1	109.5
O1—P—O3	108.21 (6)	C7—C2—C3	118.49 (13)
O2—P—O3	108.92 (6)	C7—C2—C1	120.66 (12)
O4—P—O3	107.61 (6)	C3—C2—C1	120.80 (12)
P—O4—H04	109.5	C3—C4—C5	119.77 (14)
P—O3—H03	109.5	C3—C4—H4	120.1
C3—N—H2N	109.5	C5—C4—H4	120.1
C3—N—H1N	109.5	C6—C7—C2	120.78 (14)
H2N—N—H1N	109.5	C6—C7—H7	119.6
C3—N—H3N	109.5	C2—C7—H7	119.6
H2N—N—H3N	109.5	C6—C5—C4	120.28 (14)
H1N—N—H3N	109.5	C6—C5—H5	119.9
C4—C3—C2	120.72 (13)	C4—C5—H5	119.9
C4—C3—N	117.74 (12)	C5—C6—C7	119.96 (15)
C2—C3—N	121.52 (11)	C5—C6—H6	120.0
O5—C1—O6	122.62 (13)	C7—C6—H6	120.0
C4—C3—C2—C7	−0.7 (2)	C2—C3—C4—C5	0.3 (2)
N—C3—C2—C7	177.54 (13)	N—C3—C4—C5	−177.99 (15)
C4—C3—C2—C1	176.77 (14)	C3—C2—C7—C6	0.6 (2)
N—C3—C2—C1	−5.0 (2)	C1—C2—C7—C6	−176.89 (15)
O5—C1—C2—C7	162.60 (15)	C3—C4—C5—C6	0.2 (3)
O6—C1—C2—C7	−15.8 (2)	C4—C5—C6—C7	−0.3 (3)
O5—C1—C2—C3	−14.8 (2)	C2—C7—C6—C5	−0.1 (3)
O6—C1—C2—C3	166.82 (14)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N—H3N···O1	0.89	1.98	2.856 (2)	167
N—H2N···O1^i	0.89	2.01	2.888 (1)	170
N—H1N···O1^ii	0.89	1.97	2.852 (2)	173
O3—H03···O2^iii	0.82	1.77	2.584 (1)	173
O4—H04···O2^iv	0.82	1.78	2.564 (2)	159
O6—H1···O3^v	0.82	1.98	2.794 (2)	174
C6—H6···O2^vi	0.93	2.67	3.399 (2)	135
C7—H7···O6	0.93	2.44	2.759 (2)	100

Symmetry codes: (i) −x−1, −y, −z+1; (ii) −x, −y, −z+1; (iii) −x, −y+1, −z+1; (iv) x−1, y, z; (v) x+1, y, z; (vi) x, y, z+1.