2,5-Dicarboxy­anilinium chloride monohydrate

The title compound, C₈H₈NO₄⁺·Cl^-·H₂O, is the chloro­hydrated form of 2-amino­benzene-1,4-dicarboxylic acid, the basic crystal structure of which is still not known. Mol­ecules are linked by classical N-H...O, O-H...O, N-H...Cl and O-H...Cl hydrogen bonds, mainly along the mol­ecular plane, into sheets built by unusual R₆⁴(26), R₆⁴(22) and R₄³(22) rings. The stacking between layers is stabilized by another N-H...Cl hydrogen bond and by [pi]-[pi] inter­actions between aromatic rings facing each other.

S1. Comment

It is known that several aromatic species with functional groups develop specific intermolecular interactions, providing tectons (specific building blocks; Hosseini, 2003) suitable for crystal engineering. In particular, aromatic carboxylic acid (Biradha et al., 1998; Ferguson et al., 1998; Félix et al., 2000) and amino groups (Bensemann et al., 2003; Karle et al., 2003) can act as hydrogen-bond donors and acceptors, keeping the direction of the hydrogen bonds approximately along the molecular plane. Often, the flat extension of such hydrogen-bond interactions leads to one-dimensional supramolecular tapes or two-dimensional supramolecular layers (Russell & Ward, 1996), whereas π–π stacking interactions will link layers into a three-dimensional framework (Glidewell et al., 2004). These substrates are widely harnessed in the design of functional organic solids, and also in the building of metal–organic scaffolds with specific properties (Shi et al., 2005; Arora & Pedireddi, 2003). 1,4-Dicarboxyl-2-aminobenzene (2-aminoterephthalic acid, 2aTPT) is well known as a ligand for metal–organic frameworks (MOFs) for systematic structural design, with possible applications in methane storage (Eddaoudi et al., 2002). Because of its interesting functional groups, in order to extend the π-conjugated system we have obtained the corresponding salicylidenimine by a condensation reaction (unpublished data). Starting from simple structural reports concerning directional intermolecular interactions (Bruno et al., 2004), we decided to move on to the study of chlorohydrated 2aTPT, (I), since suitable crystals were obtained from water–methanol solutions.

Compound (I) crystallizes in the P2₁/c space group. The asymmetric unit contains one 1,4-dicarboxybenzene-2-ammonium cation, a Cl⁻ counterion and a water molecule. The aromatic cation presents a planar conformation [maximum deviation from the mean molecular plane for atom O2 = 0.108 (5) Å; see also geometric parameters in Table 1].

The crystal packing of (I) is mainly stabilized by classical hydrogen bonds involving the water molecule and the Cl⁻ anion (Table 2). As the O—H and N—H groups are hydrogen-bond donors along the molecular plane, linked to coplanar acceptors, the development of a corrugated supramolecular layer is observed. In this bidimensional array lying roughly along the (201) crystallographic plane, several repeating ring units, determined by the above-mentioned hydrogen bonds, can be distinguished. The surface is covered by two centrosymmetric hexagon-shaped units, with graph-set motifs (Bernstein et al., 1995) of R₆⁴(26) and R₆⁴(22), and by a triangular ring, with graph-set R₄³(15) (Fig. 2). Along the perpendicular direction, the undulating sheets are stacked by a vertical hydrogen bond [N8···Cl1ⁱ = 3.229 (3) Å, H8C···Cl1ⁱ = 2.35 Å and N8—H8C···Cl1ⁱ = 167.4°; symmetry code: (i) x, −y + 3/2, z − 1/2] and also by π–π interactions; the distance between close aromatic rings facing each other is 3.374 Å.

S2. Experimental

2aTPT (4 mg) was dissolved in hot methanol (5 ml) and then 1M aqueous hydrochloric acid (35 µl) was added. Brown crystals of (I) suitable for X-ray analysis were obtained after slow evaporation of the resulting mixture.

S3. Refinement

H atoms were located in a difference Fourier map and placed in idealized positions using the riding-model technique, with C—H = 0.93 Å, N—H = 0.89 Å and O—H = 0.82 Å, and with U_iso(H) = 1.2U_eq(C) or 1.5U_eq(N,O) [Please check added text]. The best refinement was obtained with the ψ-scan (North et al., 1968) absorption correction performed by XSCANS (Siemens, 1989).

Computing details

Data collection: P3/V (Bruker, 1989); cell refinement: P3/V; data reduction: XDISK (Bruker, 1989); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Bruker, 1997); software used to prepare material for publication: PARST97 (Nardelli, 1995) and WinGX-PC (Version 1.6.4.05; Farrugia, 1999).

Figures

	Fig. 1. A view of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii. Dotted lines indicate hydrogen bonds.
	Fig. 2. A perpendicular view of the (201) crystallographic plane covered by R6^4(26), R6^4(22) and R4^3(15) rings, whose disposition is shown also in the schematic representation. Dotted lines indicate hydrogen bonds.

2,5-Dicarboxyanilinium chloride monohydrate

Crystal data

C8H8NO4^+·Cl^−·H2O	F(000) = 488
Mr = 235.62	Dx = 1.591 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 30 reflections
a = 6.517 (1) Å	θ = 15–30°
b = 16.670 (3) Å	µ = 0.39 mm^−1
c = 9.560 (2) Å	T = 298 K
β = 108.69 (2)°	Irregular, brown
V = 983.8 (3) Å^3	0.40 × 0.19 × 0.11 mm
Z = 4

Data collection

Bruker P3 diffractometer	Rint = 0.024
ω/2θ scans	θmax = 25.1°, θmin = 2.4°
Absorption correction: ψ scan (North et al., 1968)	h = −1→7
Tmin = 0.860, Tmax = 0.962	k = −1→19
2395 measured reflections	l = −11→11
1741 independent reflections	1 standard reflections every 50 reflections
1155 reflections with I > 2σ(I)	intensity decay: none

Refinement

Refinement on F^2	3 restraints
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.043	w = 1/[σ^2(Fo^2) + (0.0478P)^2 + 0.3568P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.117	(Δ/σ)max = 0.008
S = 1.04	Δρmax = 0.25 e Å^−3
1743 reflections	Δρmin = −0.23 e Å^−3
140 parameters

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.

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

	x	y	z	Uiso*/Ueq
C1	0.6959 (5)	0.89096 (16)	0.1039 (3)	0.0327 (7)
C2	0.5401 (5)	0.86214 (15)	0.1624 (3)	0.0310 (7)
C3	0.4424 (5)	0.91096 (16)	0.2384 (3)	0.0346 (7)
H3	0.3387	0.8905	0.2765	0.042*
C4	0.5019 (5)	0.99215 (15)	0.2575 (3)	0.0305 (6)
C5	0.6607 (5)	1.02127 (17)	0.2045 (3)	0.0382 (7)
H5	0.7037	1.0746	0.2203	0.046*
C6	0.7557 (5)	0.97153 (16)	0.1283 (3)	0.0352 (7)
H6	0.8619	0.9919	0.0924	0.042*
C7	0.7865 (5)	0.83905 (18)	0.0116 (3)	0.0360 (7)
N8	0.4741 (5)	0.77770 (13)	0.1451 (3)	0.0438 (7)
H8A	0.3924	0.7671	0.2017	0.066*
H8B	0.5912	0.7466	0.172	0.066*
H8C	0.3985	0.7682	0.0511	0.066*
C9	0.3929 (5)	1.04754 (17)	0.3341 (3)	0.0394 (8)
O10	0.7172 (4)	0.77266 (12)	−0.0302 (2)	0.0493 (6)
O11	0.9458 (4)	0.87355 (12)	−0.0228 (2)	0.0495 (6)
H11	0.9902	0.8429	−0.0738	0.074*
O12	0.4395 (4)	1.11797 (12)	0.3518 (3)	0.0622 (7)
O13	0.2440 (4)	1.01330 (12)	0.3797 (2)	0.0480 (6)
H13	0.1896	1.0469	0.4197	0.072*
O14	0.9600 (5)	0.61422 (14)	0.0047 (3)	0.0626 (7)
H14A	1.0218	0.6244	−0.0702	0.094*
H14B	0.8769	0.6604	0.0053	0.094*
Cl1	0.13607 (15)	0.74474 (5)	0.31639 (9)	0.0519 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0379 (18)	0.0301 (15)	0.0314 (14)	0.0011 (14)	0.0129 (13)	0.0000 (11)
C2	0.0431 (19)	0.0210 (13)	0.0311 (14)	0.0013 (14)	0.0150 (14)	−0.0001 (11)
C3	0.0444 (19)	0.0295 (15)	0.0346 (15)	−0.0033 (14)	0.0194 (14)	0.0010 (12)
C4	0.0382 (17)	0.0253 (13)	0.0288 (13)	0.0040 (13)	0.0120 (13)	0.0003 (11)
C5	0.048 (2)	0.0280 (15)	0.0412 (15)	−0.0041 (15)	0.0174 (15)	−0.0021 (13)
C6	0.0371 (18)	0.0320 (15)	0.0399 (15)	−0.0062 (14)	0.0169 (14)	0.0009 (13)
C7	0.0375 (19)	0.0353 (16)	0.0386 (15)	−0.0030 (15)	0.0168 (15)	−0.0018 (13)
N8	0.0651 (19)	0.0274 (13)	0.0507 (15)	−0.0022 (13)	0.0350 (14)	0.0006 (11)
C9	0.050 (2)	0.0305 (16)	0.0383 (16)	0.0051 (16)	0.0149 (16)	−0.0001 (13)
O10	0.0560 (15)	0.0422 (13)	0.0621 (14)	−0.0081 (12)	0.0362 (12)	−0.0141 (11)
O11	0.0524 (16)	0.0457 (13)	0.0649 (14)	−0.0088 (12)	0.0390 (13)	−0.0113 (11)
O12	0.094 (2)	0.0256 (11)	0.0848 (17)	−0.0011 (13)	0.0527 (16)	−0.0085 (11)
O13	0.0564 (15)	0.0379 (12)	0.0615 (13)	0.0008 (12)	0.0357 (12)	−0.0092 (10)
O14	0.074 (2)	0.0506 (14)	0.0774 (17)	−0.0058 (14)	0.0451 (15)	0.0108 (12)
Cl1	0.0633 (6)	0.0487 (5)	0.0570 (5)	−0.0027 (5)	0.0380 (5)	0.0060 (4)

Geometric parameters (Å, º)

C1—C2	1.392 (4)	C7—O10	1.214 (3)
C1—C6	1.397 (4)	C7—O11	1.318 (3)
C1—C7	1.487 (4)	N8—H8A	0.89
C2—C3	1.375 (4)	N8—H8B	0.89
C2—N8	1.466 (3)	N8—H8C	0.89
C3—C4	1.403 (4)	C9—O12	1.211 (3)
C3—H3	0.93	C9—O13	1.315 (4)
C4—C5	1.378 (4)	O11—H11	0.82
C4—C9	1.492 (4)	O13—H13	0.82
C5—C6	1.375 (4)	O14—H14A	0.9419
C5—H5	0.93	O14—H14B	0.9419
C6—H6	0.93
C2—C1—C6	117.7 (3)	C1—C6—H6	119.4
C2—C1—C7	121.1 (2)	O10—C7—O11	123.8 (3)
C6—C1—C7	121.1 (3)	O10—C7—C1	123.3 (3)
C3—C2—C1	121.9 (2)	O11—C7—C1	112.9 (2)
C3—C2—N8	117.4 (3)	C2—N8—H8A	109.5
C1—C2—N8	120.8 (2)	C2—N8—H8B	109.5
C2—C3—C4	119.0 (3)	H8A—N8—H8B	109.5
C2—C3—H3	120.5	C2—N8—H8C	109.5
C4—C3—H3	120.5	H8A—N8—H8C	109.5
C5—C4—C3	120.0 (3)	H8B—N8—H8C	109.5
C5—C4—C9	119.6 (3)	O12—C9—O13	123.6 (3)
C3—C4—C9	120.4 (3)	O12—C9—C4	122.1 (3)
C6—C5—C4	120.1 (3)	O13—C9—C4	114.3 (2)
C6—C5—H5	120	C7—O11—H11	109.5
C4—C5—H5	120	C9—O13—H13	109.5
C5—C6—C1	121.3 (3)	H14A—O14—H14B	104.2
C5—C6—H6	119.4
C6—C1—C2—C3	1.8 (4)	C2—C1—C6—C5	−1.5 (4)
C7—C1—C2—C3	−174.9 (3)	C7—C1—C6—C5	175.2 (3)
C6—C1—C2—N8	−178.1 (3)	C2—C1—C7—O10	7.5 (5)
C7—C1—C2—N8	5.2 (4)	C6—C1—C7—O10	−169.0 (3)
C1—C2—C3—C4	0.0 (4)	C2—C1—C7—O11	−174.1 (3)
N8—C2—C3—C4	179.9 (3)	C6—C1—C7—O11	9.4 (4)
C2—C3—C4—C5	−2.0 (4)	C5—C4—C9—O12	−0.1 (4)
C2—C3—C4—C9	177.5 (3)	C3—C4—C9—O12	−179.7 (3)
C3—C4—C5—C6	2.3 (4)	C5—C4—C9—O13	179.9 (3)
C9—C4—C5—C6	−177.2 (3)	C3—C4—C9—O13	0.3 (4)
C4—C5—C6—C1	−0.5 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N8—H8A···Cl1	0.89	2.3	3.186 (3)	171
N8—H8B···O12^i	0.89	2.16	2.720 (3)	120
N8—H8C···Cl1^ii	0.89	2.35	3.229 (3)	168
O11—H11···Cl1^iii	0.82	2.19	3.002 (2)	173
O13—H13···O14^iv	0.82	1.78	2.600 (3)	173

Symmetry codes: (i) −x+1, y−1/2, −z+1/2; (ii) x, −y+3/2, z−1/2; (iii) x+1, −y+3/2, z−1/2; (iv) −x+1, y+1/2, −z+1/2.