Hydrogen bonding in 4-carboxy­anilinium dihydrogenphosphate

The crystal structure analysis of the title compound, C₇H₈NO₂⁺·H₂PO₄⁻, has revealed a three-dimensional hydrogen-bonded network structure, involving the dihydrogenphosphate anions, the carboxyl groups and the ammonium groups. The anions are held together via strong O—H...O hydrogen bonds. In addition to the N—H...O and O—H...O inter­actions, involving all the H atoms covalently bonded to the anion, the nitro­gen and the carboxyl group, the crystal structure is also stabilized by C—H...O and C—H...π short contacts.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.043
• wR factor = 0.120
• Data-to-parameter ratio = 20.5

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT411_ALERT_2_B Short Inter H...H Contact  H7     ..  H7      ..       2.05 Ang.

Alert level C
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       2.69 Ratio
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for         C7
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         C5
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       3.35
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          2

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
   1 ALERT level B = Potentially serious problem
   6 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
   5 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

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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).

4-carboxyanilinium dihydrogenphosphate

Crystal data

C7H8O2N^+·H2PO4^−	F(000) = 488
Mr = 235.13	Dx = 1.564 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 14125 reflections
a = 6.3368 (2) Å	θ = 1.8–30.0°
b = 22.8812 (7) Å	µ = 0.29 mm^−1
c = 7.3843 (2) Å	T = 293 K
β = 111.101 (2)°	Prism, yellow
V = 998.88 (5) Å^3	0.20 × 0.15 × 0.10 mm
Z = 4

Data collection

Nonius KappaCCD diffractometer	2428 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.080
Graphite monochromator	θmax = 30.0°, θmin = 1.8°
ω–θ scans	h = −8→7
13869 measured reflections	k = −30→32
2865 independent reflections	l = −9→10

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)] = 0.043	Hydrogen site location: difference Fourier map
wR(F^2) = 0.120	H-atom parameters constrained
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0565P)^2 + 0.4244P] where P = (Fo^2 + 2Fc^2)/3
2865 reflections	(Δ/σ)max < 0.001
140 parameters	Δρmax = 0.33 e Å^−3
0 restraints	Δρmin = −0.49 e Å^−3

Special details

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.

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

	x	y	z	Uiso*/Ueq
C1	1.0670 (3)	−0.04346 (7)	0.7651 (3)	0.0392 (4)
C2	0.9894 (3)	0.01820 (7)	0.7557 (3)	0.0378 (4)
C3	1.1391 (3)	0.06177 (7)	0.8476 (3)	0.0390 (4)
H3	1.2899	0.0527	0.9165	0.047*
C4	1.0659 (3)	0.11934 (7)	0.8378 (3)	0.0374 (4)
H4	1.1669	0.1488	0.9002	0.045*
C5	0.8433 (3)	0.13227 (6)	0.7352 (2)	0.0286 (3)
C6	0.6919 (3)	0.08934 (8)	0.6440 (4)	0.0679 (8)
H6	0.5411	0.0985	0.5755	0.081*
C7	0.7666 (4)	0.03227 (9)	0.6552 (5)	0.0767 (9)
H7	0.6647	0.0029	0.5938	0.092*
N	0.7623 (2)	0.19231 (5)	0.72118 (19)	0.0282 (3)
H3N	0.8791	0.2163	0.7740	0.042*
H1N	0.6666	0.1957	0.7840	0.042*
H2N	0.6918	0.2017	0.5969	0.042*
O1	0.5975 (2)	0.22678 (5)	0.34225 (17)	0.0383 (3)
O2	0.97008 (19)	0.18530 (5)	0.35406 (17)	0.0367 (3)
O3	0.7928 (2)	0.26495 (5)	0.12318 (18)	0.0380 (3)
H03	0.6740	0.2766	0.0420	0.057*
O4	0.6195 (2)	0.16719 (5)	0.06137 (17)	0.0358 (3)
H04	0.6509	0.1335	0.0995	0.054*
O5	1.2623 (2)	−0.05767 (6)	0.8532 (2)	0.0530 (4)
O6	0.9066 (2)	−0.08001 (6)	0.6700 (3)	0.0566 (4)
H1	0.9613	−0.1125	0.6694	0.085*
P	0.74424 (6)	0.210878 (16)	0.23096 (5)	0.02623 (13)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0373 (8)	0.0258 (7)	0.0452 (9)	0.0032 (6)	0.0037 (7)	−0.0033 (6)
C2	0.0353 (8)	0.0246 (7)	0.0440 (9)	0.0027 (6)	0.0030 (7)	−0.0025 (6)
C3	0.0284 (7)	0.0286 (7)	0.0526 (10)	0.0016 (6)	0.0055 (7)	0.0019 (7)
C4	0.0302 (7)	0.0244 (7)	0.0497 (9)	−0.0029 (6)	0.0048 (7)	−0.0005 (6)
C5	0.0302 (7)	0.0223 (6)	0.0316 (7)	0.0006 (5)	0.0093 (6)	0.0002 (5)
C6	0.0320 (9)	0.0295 (9)	0.1066 (19)	0.0051 (7)	−0.0181 (11)	−0.0166 (10)
C7	0.0390 (10)	0.0282 (9)	0.120 (2)	0.0026 (7)	−0.0237 (12)	−0.0207 (11)
N	0.0294 (6)	0.0234 (6)	0.0326 (6)	0.0017 (4)	0.0120 (5)	0.0005 (4)
O1	0.0436 (7)	0.0390 (6)	0.0357 (6)	0.0138 (5)	0.0185 (5)	0.0061 (5)
O2	0.0313 (5)	0.0281 (5)	0.0381 (6)	0.0081 (4)	−0.0029 (5)	−0.0069 (4)
O3	0.0286 (5)	0.0369 (6)	0.0437 (7)	−0.0026 (4)	0.0072 (5)	0.0102 (5)
O4	0.0335 (6)	0.0300 (5)	0.0342 (6)	0.0020 (4)	0.0005 (5)	−0.0037 (4)
O5	0.0399 (7)	0.0288 (6)	0.0729 (10)	0.0069 (5)	−0.0009 (6)	−0.0029 (6)
O6	0.0427 (7)	0.0259 (6)	0.0797 (10)	0.0055 (5)	−0.0040 (7)	−0.0140 (6)
P	0.02511 (19)	0.0232 (2)	0.0271 (2)	0.00395 (12)	0.00541 (14)	0.00016 (13)

Geometric parameters (Å, º)

P—O1	1.4908 (13)	N—H3N	0.8900
P—O2	1.5100 (13)	C1—C2	1.488 (2)
P—O3	1.5605 (13)	C2—C7	1.376 (4)
P—O4	1.5747 (12)	C2—C3	1.375 (3)
O5—C1	1.217 (2)	C3—C4	1.390 (2)
O6—C1	1.308 (2)	C4—C5	1.372 (3)
O6—H1	0.8200	C5—C6	1.369 (3)
O3—H03	0.8200	C6—C7	1.381 (3)
O4—H04	0.8200	C3—H3	0.9300
N—C5	1.4571 (19)	C4—H4	0.9300
N—H2N	0.8900	C6—H6	0.9300
N—H1N	0.8900	C7—H7	0.9300
O2—P—O3	107.23 (7)	C1—C2—C7	120.32 (17)
O2—P—O4	109.17 (7)	C3—C2—C7	119.22 (17)
O3—P—O4	103.44 (7)	C1—C2—C3	120.46 (18)
O1—P—O2	114.00 (7)	C2—C3—C4	120.23 (19)
O1—P—O3	111.36 (7)	C3—C4—C5	119.39 (17)
O1—P—O4	111.05 (7)	N—C5—C4	120.56 (14)
C1—O6—H1	109.00	N—C5—C6	118.36 (16)
P—O3—H03	109.00	C4—C5—C6	121.08 (15)
P—O4—H04	109.00	C5—C6—C7	119.0 (2)
C5—N—H3N	110.00	C2—C7—C6	121.1 (2)
H1N—N—H2N	109.00	C4—C3—H3	120.00
H2N—N—H3N	109.00	C2—C3—H3	120.00
C5—N—H1N	110.00	C5—C4—H4	120.00
C5—N—H2N	110.00	C3—C4—H4	120.00
H1N—N—H3N	109.00	C5—C6—H6	120.00
O6—C1—C2	113.66 (17)	C7—C6—H6	121.00
O5—C1—O6	124.07 (16)	C2—C7—H7	119.00
O5—C1—C2	122.27 (17)	C6—C7—H7	119.00
O5—C1—C2—C3	0.2 (3)	C3—C2—C7—C6	0.5 (4)
O5—C1—C2—C7	−179.7 (2)	C2—C3—C4—C5	−0.2 (3)
O6—C1—C2—C3	−179.6 (2)	C3—C4—C5—N	−179.50 (17)
O6—C1—C2—C7	0.6 (3)	C3—C4—C5—C6	0.6 (3)
C1—C2—C3—C4	179.77 (19)	N—C5—C6—C7	179.7 (2)
C7—C2—C3—C4	−0.4 (3)	C4—C5—C6—C7	−0.5 (3)
C1—C2—C7—C6	−179.6 (2)	C5—C6—C7—C2	−0.1 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O6—H1···O2^i	0.82	1.75	2.5586 (18)	170
O3—H03···O2^ii	0.82	1.75	2.5497 (17)	164
N—H1N···O4^iii	0.89	2.27	3.0160 (18)	141
N—H1N···O3^iv	0.89	2.41	2.9633 (19)	121
O4—H04···O5^i	0.82	1.82	2.6265 (18)	170
N—H2N···O1	0.89	1.85	2.7273 (17)	169
N—H3N···O1^v	0.89	1.83	2.7150 (18)	170
C7—H7···O6	0.93	2.38	2.707 (3)	101

Symmetry codes: (i) −x+2, −y, −z+1; (ii) x−1/2, −y+1/2, z−1/2; (iii) x, y, z+1; (iv) x−1/2, −y+1/2, z+1/2; (v) x+1/2, −y+1/2, z+1/2.