4-Iodo­anilinium 3-nitro­phthalate(1-): tripartite sheets built from O-H...O and N-H...O hydrogen bonds

In the title compound, 4-iodoanilinium 2-carboxy-6-nitrobenzoate, C₆H₇IN⁺·C₈H₄NO₆^-, the anions are linked by an O-H...O hydrogen bond [H...O = 1.78 Å, O...O = 2.614 (3) Å and O-H...O = 171°] into C(7) chains, and these chains are linked by two two-centre N-H...O hydrogen bonds [H...O = 1.86 and 1.92 Å, N...O = 2.700 (3) and 2.786 (3) Å, and N-H...O = 153 and 158°] and one three-centre N-H...(O)₂ hydrogen bond [H...O = 2.02 and 2.41 Å, N...O = 2.896 (3) and 2.789 (3) Å, N-H...O = 162 and 105°, and O...H...O = 92°], thus forming sheets con­taining R₂²(6), R₄²(8), R₃³(13) and R₄⁴(18) rings.

S1. Comment

The reaction of anilines with phthalic anhydrides under anhydrous conditions generally yields N-aryl phthalimides, but in the presence of water, anilinium salts can be formed. We report here the molecular and supramolecular structure of the title compound, (I), in which the ionic components are linked into hydrogen-bonded sheets. Compound (I) is a salt (IC₆H₄NH₃)⁺[C₆H₃(COOH)(COO)(NO₂)]⁻ in which there has been complete transfer to the amine of one H atom from the carboxyl group adjacent to the nitro substituent (Fig. 1).

The nitro group is almost coplanar with the adjacent aryl ring, but the carboxylate substituent lying between the nitro group and the unionized carboxyl substituent is nearly orthogonal to the plane of the adjacent ring, with a dihedral angle between the C1–C6 and C2/C21/O21/O22 mean planes of 80.4 (4)°. For the unionized carboxyl group, the dihedral angle between planes C1–C6 and C1/C11/O11/O12 is only 26.7 (2)°. The rotation of the carboxylate substituent on atom C2 can be ascribed to steric congestion, which would result from three adjacent substituents if all were coplanar with the aryl ring; even so, there is evidence in the exocyclic bond angles at atoms C1 and C3 of some steric compression, as the C2—C1—C11 and C2—C3—N31 angles are both significantly larger than 120°, while the C6—C1—C11 and C4—C3—N31 angles are both much smaller than 120° (Table 1). In addition, the exocyclic C1—C11, C2—C21 and C3—N31 distances are all larger than the upper-quartile values for bonds of these types (1.491, 1.512 and 1.476 Å, respectively; Allen et al., 1987). The C—O distances in the anion are fully consistent with the location of the H atoms as deduced from difference maps, and the O—C—O angle in the ionized carboxylate group is significantly larger than that in the unionized substituent.

The ions are linked by O—H···O and N—H···O hydrogen bonds into sheets. In the asymmetric unit (Fig. 1), the ions are linked by an N—H···O hydrogen bond, which can be regarded as the shorter and stronger component of a three-centre N—H···(O)₂ system (Table 2) in which the sum of the angles at H1A is 359°. The analysis and description of the supramolecular structure are most readily approached in terms of the one-dimensional substructure generated by the anions. Carboxyl atom O12 in the anion at (x, y, z) acts as a hydrogen-bond donor to carboxylate atom O22 in the anion at (1 − x, −0.5 + y, 0.5 − z), so producing a C(7) chain (Bernstein et al., 1995) running parallel to the [010] direction and generated by the 2₁ screw axis along (1/2, y, 1/4) (Fig. 2). A second chain of this type, antiparallel to the first and related to it by inversion, is generated by the 2₁ axis along (1/2, −y, 3/4). The [010] chains are linked into sheets by the cations.

Ammonium atom N41 in the cation forms N—H···O hydrogen bonds to four different anions, which themselves lie in two different [010] chains. Atom N41 at (x, y, z) acts as a hydrogen-bond donor, via atom H41A, to atom O22 in the anion at (x, y, z) and (more weakly) to atom O11 in the anion at (1 − x, 0.5 + y, 0.5 − z), and, via atom H41C, to atom O21 in the anion at (1 − x, −0.5 + y, 0.5 − z). These three anions all lie in the C(7) anion chain along (1/2, y, 1/4). In addition, atom N41 at (x, y, z) acts as a donor, via atom H41B, to atom O21 in the anion at (x, 1.5 − y, −0.5 + z), which is a component of the anion chain along (1/2, −y, −0.25). Propagation by the space group of these hydrogen bonds thus links together all of the anion chains generated by 2₁ screw axes having x = 1/2, so forming a tripartite (100) sheet in which the –NH₃⁺, –COOH and –COO⁻ functions lie in the central layer, with the iodophenyl and nitroaryl units forming the two outer layers (Fig. 3). Note that, although the two O atoms of the ionized carboxylate group, O21 and O22, both act as double acceptors of hydrogen bonds, neither of the O atoms in the nitro group plays any role in the supramolecular aggregation.

The complexity of the hydrogen bonding in the (100) sheet is illustrated by the occurrence of four distinct types of ring motif within the sheet. The three-centre N—H···(O)₂– hydrogen bond involving atom H41A represents a two-point attachment of the cation to an anion chain, producing an R²₂(6) motif (Bernstein et al., 1995) that also involves atom H12 (Fig. 3). Hydrogen bonds involving atoms H41A and H41B generate centrosymmetric R⁴₄(18) rings, centred at (1/2, 1, 0) and (1/2, 1/2, 1/2); hydrogen bonds involving atoms H41B and H41C generate centrosymmetric R²₄(8) rings centred at (1/2, 1/2, 0) and (1/2, 1, 1/2); and hydrogen bonds involving atoms H41C and H41A generate R³₃(13) rings, which form chains of edge-fused rings along [010].

There is only one contact of possible significance between adjacent (100) sheets. Atom I44 at (x, y, z) and (-x, −y, −z) are separated by 3.541 (3) Å and the C—I···Iⁱ angle is 149.1 (2)° [symmetry code: (i) −x, −y, −z]. Adopting the lower limit (1.95 Å) of the van der Waals radii for I as given by Bondi (1964), this contact appears to be very short. However, the polar flattening model (Nyburg & Faerman, 1985) developed from an extensive analysis of structures from the Cambridge Structural Database (Allen, 2002) gives a `minor radius' for I of only 1.76 Å, indicating a limiting I···I distances for near-linear approaches almost identical to that observed here. Hence we do not regard this I···I contact either as anomalously short or as having structural significance.

S2. Experimental

Equimolar quantities of 4-iodoaniline and 3-nitrophthalic anhydride were heated together in the presence of excess water. After cooling the mixture to ambient temperature, crystallization from ethanol provided crystals of (I) suitable for single-crystal X-ray diffraction.

S3. Refinement

Crystals of (I) are monoclinic and the space group P2₁/c was uniquely assigned from the systematic absences. All H atoms were located from difference maps and were subsequently treated as riding atoms with C—H distances of 0.95 Å, N—H distances of 0.91 Å and O—H distances of 0.84 Å.

Computing details

Data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: DENZO–SMN (Otwinowski & Minor, 1997); data reduction: DENZO–SMN (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997) and PRPKAPPA (Ferguson, 1999).

Figures

	Fig. 1. The independent components of compound (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.
	Fig. 2. Part of the crystal structure of (I), showing the formation of a C(7) chain of anions. For clarity, H atoms bonded to C atoms have been omitted. Atoms marked with an asterisk (*), a hash (#) or a dollar sign ($) are at the symmetry positions (1 − x, −0.5 + y, 0.5 − z), (x, −1 + y, z) and (1 − x, 0.5 + y, 0.5 − z), respectively.
	Fig. 3. Stereoview of part of the crystal structure of (I), showing the formation of a (100) sheet. For clarity, H atoms bonded to C atoms have been omitted.

4-Iodoanilinium 3-nitrophthalate(1-)

Crystal data

C6H7IN^+·C8H4NO6^−	F(000) = 840
Mr = 430.15	Dx = 1.879 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3460 reflections
a = 14.7434 (5) Å	θ = 3.1–27.5°
b = 8.1274 (2) Å	µ = 2.14 mm^−1
c = 13.2487 (4) Å	T = 120 K
β = 106.7116 (12)°	Block, colourless
V = 1520.48 (8) Å^3	0.32 × 0.20 × 0.18 mm
Z = 4

Data collection

Nonius KappaCCD diffractometer	3460 independent reflections
Radiation source: rotating anode	2898 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.051
ϕ scans, and ω scans with κ offsets	θmax = 27.5°, θmin = 3.1°
Absorption correction: multi-scan DENZO–SMN (Otwinowski & Minor, 1997)	h = −19→19
Tmin = 0.532, Tmax = 0.678	k = −10→10
17530 measured reflections	l = −17→17

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)] = 0.029	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.068	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0247P)^2 + 2.0308P] where P = (Fo^2 + 2Fc^2)/3
3460 reflections	(Δ/σ)max < 0.001
210 parameters	Δρmax = 1.11 e Å^−3
0 restraints	Δρmin = −0.75 e Å^−3

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

	x	y	z	Uiso*/Ueq
C1	0.32068 (19)	0.5625 (3)	0.3155 (2)	0.0168 (5)
C2	0.29669 (18)	0.7288 (3)	0.29216 (19)	0.0134 (5)
C3	0.20226 (19)	0.7704 (3)	0.2792 (2)	0.0158 (5)
C4	0.1324 (2)	0.6570 (3)	0.2809 (2)	0.0211 (6)
C5	0.1573 (2)	0.4936 (3)	0.2985 (2)	0.0228 (6)
C6	0.2512 (2)	0.4480 (3)	0.3188 (2)	0.0206 (6)
C11	0.41958 (19)	0.4935 (3)	0.3393 (2)	0.0178 (6)
O11	0.44194 (15)	0.3702 (3)	0.39107 (18)	0.0335 (5)
O12	0.47691 (13)	0.5749 (2)	0.29652 (14)	0.0173 (4)
C21	0.37178 (18)	0.8537 (3)	0.2836 (2)	0.0128 (5)
O21	0.42541 (12)	0.9072 (2)	0.36848 (13)	0.0162 (4)
O22	0.37593 (12)	0.8888 (2)	0.19247 (13)	0.0159 (4)
N31	0.17229 (16)	0.9453 (3)	0.26929 (17)	0.0188 (5)
O31	0.23225 (14)	1.0492 (2)	0.26918 (17)	0.0263 (5)
O32	0.08997 (14)	0.9770 (3)	0.26408 (17)	0.0287 (5)
C41	0.33741 (18)	0.5224 (3)	0.06133 (19)	0.0152 (5)
N41	0.42149 (15)	0.6224 (3)	0.07019 (16)	0.0152 (4)
C42	0.34716 (19)	0.3537 (3)	0.0758 (2)	0.0187 (6)
C43	0.2665 (2)	0.2590 (3)	0.0653 (2)	0.0205 (6)
C44	0.1789 (2)	0.3353 (3)	0.0396 (2)	0.0190 (6)
I44	0.056953 (13)	0.19396 (2)	0.023028 (16)	0.02850 (8)
C45	0.1698 (2)	0.5048 (3)	0.0253 (2)	0.0209 (6)
C46	0.25039 (19)	0.5993 (3)	0.0368 (2)	0.0183 (5)
H4	0.0687	0.6912	0.2702	0.025*
H5	0.1102	0.4129	0.2968	0.027*
H6	0.2687	0.3365	0.3352	0.025*
H12	0.5275	0.5219	0.3056	0.026*
H41A	0.4174	0.7172	0.1051	0.023*
H41B	0.4256	0.6468	0.0046	0.023*
H41C	0.4739	0.5655	0.1064	0.023*
H42	0.4079	0.3037	0.0926	0.022*
H43	0.2714	0.1433	0.0757	0.025*
H45	0.1091	0.5551	0.0079	0.025*
H46	0.2458	0.7152	0.0278	0.022*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0197 (14)	0.0164 (12)	0.0160 (12)	0.0010 (10)	0.0078 (11)	0.0008 (10)
C2	0.0175 (13)	0.0128 (12)	0.0104 (11)	−0.0015 (10)	0.0051 (10)	−0.0012 (9)
C3	0.0177 (14)	0.0151 (12)	0.0154 (12)	0.0015 (10)	0.0057 (10)	0.0014 (10)
C4	0.0167 (14)	0.0267 (14)	0.0212 (14)	−0.0011 (11)	0.0073 (11)	−0.0005 (12)
C5	0.0226 (15)	0.0204 (13)	0.0274 (15)	−0.0077 (11)	0.0105 (12)	0.0000 (12)
C6	0.0280 (16)	0.0132 (12)	0.0236 (14)	−0.0039 (11)	0.0123 (12)	−0.0003 (11)
C11	0.0227 (15)	0.0128 (12)	0.0206 (13)	0.0006 (10)	0.0103 (11)	−0.0010 (11)
O11	0.0350 (13)	0.0244 (11)	0.0477 (14)	0.0122 (10)	0.0226 (11)	0.0204 (10)
O12	0.0180 (10)	0.0147 (9)	0.0208 (9)	0.0038 (7)	0.0081 (8)	0.0031 (8)
C21	0.0135 (13)	0.0087 (10)	0.0174 (13)	0.0036 (9)	0.0063 (10)	−0.0018 (10)
O21	0.0176 (10)	0.0151 (8)	0.0155 (9)	−0.0009 (7)	0.0043 (8)	−0.0018 (7)
O22	0.0192 (10)	0.0148 (9)	0.0143 (9)	−0.0004 (7)	0.0059 (7)	0.0009 (7)
N31	0.0192 (12)	0.0184 (11)	0.0192 (11)	0.0025 (9)	0.0061 (9)	0.0008 (9)
O31	0.0237 (11)	0.0142 (9)	0.0416 (12)	−0.0005 (8)	0.0105 (9)	−0.0014 (9)
O32	0.0176 (11)	0.0291 (11)	0.0417 (12)	0.0092 (9)	0.0120 (9)	0.0060 (10)
C41	0.0178 (13)	0.0151 (12)	0.0131 (12)	−0.0022 (10)	0.0050 (10)	−0.0033 (10)
N41	0.0192 (12)	0.0126 (10)	0.0142 (10)	0.0009 (9)	0.0052 (9)	0.0003 (8)
C42	0.0170 (14)	0.0157 (12)	0.0235 (14)	0.0019 (10)	0.0062 (11)	0.0001 (11)
C43	0.0238 (15)	0.0137 (12)	0.0247 (14)	−0.0014 (11)	0.0079 (12)	−0.0008 (11)
C44	0.0188 (14)	0.0188 (13)	0.0200 (13)	−0.0041 (10)	0.0066 (11)	−0.0014 (11)
I44	0.01949 (12)	0.02430 (11)	0.04154 (14)	−0.00573 (7)	0.00850 (9)	−0.00063 (8)
C45	0.0181 (14)	0.0209 (13)	0.0225 (14)	0.0023 (11)	0.0042 (11)	−0.0005 (11)
C46	0.0215 (14)	0.0144 (12)	0.0183 (13)	0.0010 (10)	0.0046 (11)	−0.0006 (10)

Geometric parameters (Å, º)

C1—C6	1.394 (4)	N31—O31	1.222 (3)
C1—C2	1.408 (3)	N31—O32	1.223 (3)
C1—C11	1.509 (4)	C41—C46	1.379 (4)
C11—O11	1.205 (3)	C41—C42	1.386 (4)
C11—O12	1.322 (3)	C41—N41	1.458 (3)
C3—N31	1.483 (3)	N41—H41A	0.91
C2—C3	1.395 (4)	N41—H41B	0.91
C2—C21	1.530 (3)	N41—H41C	0.91
C21—O21	1.252 (3)	C42—C43	1.390 (4)
C21—O22	1.259 (3)	C42—H42	0.95
C3—C4	1.388 (4)	C43—C44	1.383 (4)
C4—C5	1.380 (4)	C43—H43	0.95
C4—H4	0.95	C44—C45	1.392 (4)
C5—C6	1.384 (4)	C44—I44	2.091 (3)
C5—H5	0.95	C45—C46	1.385 (4)
C6—H6	0.95	C45—H45	0.95
O12—H12	0.84	C46—H46	0.95
C6—C1—C2	120.5 (2)	O31—N31—C3	117.7 (2)
C2—C1—C11	124.7 (2)	O32—N31—C3	118.2 (2)
C6—C1—C11	114.8 (2)	C46—C41—C42	122.2 (2)
C1—C2—C3	116.0 (2)	C46—C41—N41	118.6 (2)
C1—C2—C21	120.8 (2)	C42—C41—N41	119.2 (2)
C3—C2—C21	123.2 (2)	C41—N41—H41A	109.5
C2—C3—C4	123.8 (2)	C41—N41—H41B	109.5
C2—C3—N31	120.3 (2)	H41A—N41—H41B	109.5
C4—C3—N31	115.7 (2)	C41—N41—H41C	109.5
C5—C4—C3	118.6 (3)	H41A—N41—H41C	109.5
C5—C4—H4	120.7	H41B—N41—H41C	109.5
C3—C4—H4	120.7	C41—C42—C43	118.8 (3)
C4—C5—C6	119.6 (3)	C41—C42—H42	120.6
C4—C5—H5	120.2	C43—C42—H42	120.6
C6—C5—H5	120.2	C44—C43—C42	119.2 (2)
C5—C6—C1	121.2 (2)	C44—C43—H43	120.4
C5—C6—H6	119.4	C42—C43—H43	120.4
C1—C6—H6	119.4	C43—C44—C45	121.6 (3)
O11—C11—O12	123.8 (3)	C43—C44—I44	119.55 (19)
O11—C11—C1	121.2 (2)	C45—C44—I44	118.9 (2)
O12—C11—C1	115.0 (2)	C46—C45—C44	119.2 (3)
C11—O12—H12	109.5	C46—C45—H45	120.4
O21—C21—O22	126.2 (2)	C44—C45—H45	120.4
O21—C21—C2	116.6 (2)	C41—C46—C45	119.0 (2)
O22—C21—C2	117.2 (2)	C41—C46—H46	120.5
O31—N31—O32	124.1 (2)	C45—C46—H46	120.5
C6—C1—C2—C3	3.6 (4)	C3—C2—C21—O21	100.1 (3)
C11—C1—C2—C3	−175.9 (2)	C1—C2—C21—O21	−78.9 (3)
C6—C1—C2—C21	−177.3 (2)	C3—C2—C21—O22	−82.2 (3)
C11—C1—C2—C21	3.2 (4)	C1—C2—C21—O22	98.7 (3)
C1—C2—C3—C4	−4.6 (4)	C4—C3—N31—O31	178.9 (2)
C21—C2—C3—C4	176.3 (2)	C2—C3—N31—O31	2.5 (4)
C1—C2—C3—N31	171.5 (2)	C4—C3—N31—O32	0.5 (3)
C21—C2—C3—N31	−7.6 (4)	C2—C3—N31—O32	−175.9 (2)
C2—C3—C4—C5	1.4 (4)	C46—C41—C42—C43	−0.1 (4)
N31—C3—C4—C5	−174.9 (2)	N41—C41—C42—C43	−178.8 (2)
C3—C4—C5—C6	3.0 (4)	C41—C42—C43—C44	0.8 (4)
C4—C5—C6—C1	−3.9 (4)	C42—C43—C44—C45	−0.8 (4)
C2—C1—C6—C5	0.5 (4)	C42—C43—C44—I44	179.8 (2)
C11—C1—C6—C5	−179.9 (2)	C43—C44—C45—C46	0.2 (4)
C6—C1—C11—O11	−24.5 (4)	I44—C44—C45—C46	179.63 (19)
C2—C1—C11—O11	155.1 (3)	C42—C41—C46—C45	−0.5 (4)
C6—C1—C11—O12	153.5 (2)	N41—C41—C46—C45	178.2 (2)
C2—C1—C11—O12	−27.0 (4)	C44—C45—C46—C41	0.5 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O12—H12···O22^i	0.84	1.78	2.614 (3)	171
N41—H41A···O22	0.91	2.02	2.896 (3)	162
N41—H41A···O11^ii	0.91	2.41	2.789 (3)	105
N41—H41B···O21^iii	0.91	1.86	2.700 (3)	153
N41—H41C···O21^i	0.91	1.92	2.786 (3)	158

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