The 2:1 complex of 4-amino­benzoic acid and 4,4′-bipyridyl N,N′-dioxide

The co-crystal C₁₀H₈N₂O₂·2C₇H₇NO₂ owes its formation to an intermolecular hydrogen bond between the O—H and N—O groups; the O...O distance is 2.5796 (17) Å. The dihedral angle between the planes of the pyridyl N-oxide and amino­benzoic rings of the complex is 10.2 (1)°. An additional intermolecular C—H...O hydrogen bond is formed, giving rise to an eight-membered ring within the asymmetric unit. The structure is centrosymmetric about the mid-point of the bond joining the two pyridine rings. The crystal structure exhibits overlap between the aromatic rings of the mol­ecules in the [10] direction.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.044
• wR factor = 0.146
• Data-to-parameter ratio = 21.2

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

---

S1. Comment

The title compound, (I), was investigated as part of a study on D—H···A hydrogen bonding in system containing 4,4'-bipyridyl N,N-dioxide and hydrogen-bond donors (Thaimattam et al., 1998). Four molecular structures similar to (I) were found in the Cambridge Structural Database (Allen, 2002), namely 4,4'-bipyridine N,N'-dioxide urea clathrate, 4,4'-bipyridine N,N'-dioxide thiourea clathrate and 4,4'-bipyridine N,N'-dioxide dihydrate clathrate (Thaimattam et al., 1998), and 4-aminobenzoic acid (Lai & Marsh, 1967), and they were used as references to analyze the structural characteristics of complex (I).

The complex is held together by a strong intermolecular hydrogen bond (Emsley, 1984) between the O—H group of 4-aminobenzoic acid (PABA) molecule and the N—O group of 4,4'-bipyridyl N,N-dioxide (DIPNO) molecule. In the crystal, two acid components related by a centre of symmetry are linked to a centrosymmetric 4,4'-bipyridyl N,N-dioxide not only by the short O—H···O bonds but also by longer C5—H5.·O3 hydrogen bonds, giving rise to an eight-membered ring within the asymmetric unit. This results in an approximately linear chaining of the three molecules. The formation of these hydrogen bonds is probably related to the rotation of the carboxylic acid group around the C9—C12 bond [the dihedral angle between this group and the C6–C11 ring being 7.5 (1)°] and to the approximate planarity of the whole centrosymmetric unit. Selected hydrogen-bond O—H···O, N—H.·O and C—H.·O interactions are presented in Table 2. A perspective view of the DIPNO–PABA (1:2) adduct showing the atomic numbering scheme is given in Fig. 1. The dihedral angle formed by the planes which essentially contain the rings of DIPNO and PABA molecules is 10.2 (1)°. The values of bond lengths and other internal parameters of DIPNO are very close to values of structures reported in the literature (Thaimattam et al., 1998). The central C3—C3ⁱ bond length [1.475 (3) Å; symmetry code: (i) −x, −y, −z] is shorter than a normal C—C single-bond distance, showing that this C—C bond has probably a little π-bond character. The presence of a strong O—H.·O and other relatively weak C—H.·O intermolecular hydrogen bonds induces some structural changes in the donor complex. Indeed, the C9—C12, C12—O2 and C12—O3 bond lengths change from 1.471 (2), 1.320 (2) and 1.218 (2) Å in (I) to 1.455 (4), 1.295 (3) and 1.248 (5) Å in the PABA molecule. There are no unusual short intermolecular bonds in the crystal structure. The molecules of PABA and DIPNO(1/2 − x, −y, z − 1/2) are overlapped along the [110] direction at a distance of 3.454 (2) Å (Fig. 2). Additionally, hydrogen-bond interactions between atom N2 with atoms O3ⁱⁱ and O1ⁱⁱⁱ of neighboring molecules [symmetry codes: (ii) ?, 1/2 − y, 1/2 + z; (iii) 1/2 + x, 1/2 − y, 1 − z] (please complete symmetry code) are observed (Fig. 3).

S2. Experimental

Single yellow crystals of the DIPNO–PABA (1:2) [m.p. 453 (1) K] suitable for X-ray analysis were obtained by slow evaporation from an equimolecular solution of DIPNO and PABA in methanol. Initial reagents were purchased from Aldrich and were used without additional purification.

S3. Refinement

All H atoms, with the exception of the carboxyl atom HO2, were added at geometrically idealized positions and were allowed for as riding; C—H = 0.86–0.93 Å and U_iso(H)= 1.2U_eq of the carrier atom. Hydroxyl atom HO2 was located from a Fourier difference map and its coordinates were refined.

Computing details

Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997) and ZORTEP (Zsolnai, 1995); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. An ORTEP-3 (Farrugia, 1997) plot of the title complex, with the atomic labelling scheme. Displacement ellipsoids are plotted at the 50% probability level. H atoms are shown as spheres of an arbitrary radius.
	Fig. 2. A ZORTEP (Zsolnai, 1995) diagram of (I), showing the overlap between the molecules along the [110] direction.
	Fig. 3. A ZORTEP (Zsolnai, 1995) view of (I), showing additional hydrogen bonds. Hydrogen-bonding interactions are indicated by dashed lines.

(I)

Crystal data

C10H8N2O2·2C7H7NO2	Dx = 1.383 Mg m^−3
Mr = 462.46	Melting point: 453(1) K
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 25 reflections
a = 11.188 (1) Å	θ = 9–18°
b = 12.138 (2) Å	µ = 0.10 mm^−1
c = 16.354 (2) Å	T = 293 K
V = 2220.9 (5) Å^3	Regular block, yellow
Z = 4	0.22 × 0.18 × 0.12 mm
F(000) = 968

Data collection

Enraf-Nonius CAD-4 diffractometer	Rint = 0.026
Radiation source: fine-focus sealed tube	θmax = 30.4°, θmin = 2.5°
Graphite monochromator	h = 0→15
ω/2θ scans	k = 0→17
6757 measured reflections	l = −23→23
3350 independent reflections	3 standard reflections every 120 min
2057 reflections with I > 2σ(I)	intensity decay: 1.9%

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)] = 0.044	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.146	H atoms treated by a mixture of independent and constrained refinement
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0639P)^2 + 0.5535P] where P = (Fo^2 + 2Fc^2)/3
3350 reflections	(Δ/σ)max < 0.001
158 parameters	Δρmax = 0.22 e Å^−3
0 restraints	Δρmin = −0.20 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.

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

	x	y	z	Uiso*/Ueq
O1	0.00584 (14)	−0.05247 (12)	0.29335 (7)	0.0715 (4)
N1	0.00521 (12)	−0.03725 (11)	0.21317 (7)	0.0498 (3)
C1	−0.06048 (16)	−0.10416 (14)	0.16603 (10)	0.0537 (4)
H1	−0.1044	−0.1606	0.1900	0.064*
C2	−0.06367 (15)	−0.09039 (13)	0.08308 (10)	0.0506 (4)
H2	−0.1100	−0.1378	0.0516	0.061*
C3	0.00058 (12)	−0.00731 (11)	0.04476 (8)	0.0378 (3)
C4	0.06638 (16)	0.06063 (14)	0.09572 (9)	0.0548 (4)
H4	0.1102	0.1182	0.0732	0.066*
C5	0.06824 (17)	0.04477 (16)	0.17887 (10)	0.0604 (5)
H5	0.1136	0.0913	0.2117	0.072*
N2	0.37505 (15)	0.33076 (15)	0.67973 (9)	0.0688 (5)
HN21	0.3506	0.3116	0.7275	0.083*
HN22	0.4262	0.3832	0.6746	0.083*
O2	0.13107 (12)	0.03202 (10)	0.41001 (7)	0.0593 (3)
HO2	0.105 (2)	0.007 (2)	0.3615 (14)	0.084 (7)*
O3	0.22365 (13)	0.15164 (12)	0.32868 (6)	0.0683 (4)
C6	0.33268 (14)	0.27774 (14)	0.61185 (9)	0.0482 (4)
C7	0.37289 (14)	0.30819 (14)	0.53363 (9)	0.0491 (4)
H7	0.4283	0.3648	0.5280	0.059*
C8	0.33072 (13)	0.25479 (13)	0.46541 (8)	0.0455 (3)
H8	0.3582	0.2758	0.4140	0.055*
C9	0.24761 (14)	0.16980 (12)	0.47180 (8)	0.0422 (3)
C10	0.20820 (15)	0.13959 (13)	0.54979 (9)	0.0482 (3)
H10	0.1530	0.0828	0.5554	0.058*
C11	0.25001 (15)	0.19266 (14)	0.61827 (9)	0.0512 (4)
H11	0.2227	0.1714	0.6696	0.061*
C12	0.20161 (14)	0.11742 (13)	0.39705 (8)	0.0461 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0988 (10)	0.0777 (9)	0.0379 (6)	−0.0287 (8)	0.0023 (6)	−0.0031 (6)
N1	0.0583 (8)	0.0512 (7)	0.0400 (6)	−0.0064 (6)	0.0022 (6)	−0.0072 (5)
C1	0.0625 (10)	0.0504 (8)	0.0481 (8)	−0.0175 (7)	0.0051 (7)	−0.0051 (7)
C2	0.0547 (9)	0.0506 (8)	0.0466 (7)	−0.0167 (7)	−0.0004 (6)	−0.0084 (6)
C3	0.0344 (6)	0.0367 (6)	0.0422 (7)	0.0006 (5)	−0.0002 (5)	−0.0077 (5)
C4	0.0657 (10)	0.0548 (9)	0.0440 (8)	−0.0244 (8)	−0.0024 (7)	−0.0052 (7)
C5	0.0735 (11)	0.0638 (10)	0.0439 (8)	−0.0277 (9)	−0.0039 (8)	−0.0089 (7)
N2	0.0718 (10)	0.0901 (12)	0.0447 (7)	−0.0115 (9)	0.0033 (7)	−0.0134 (8)
O2	0.0802 (8)	0.0535 (7)	0.0442 (6)	−0.0097 (6)	−0.0040 (6)	0.0031 (5)
O3	0.0837 (9)	0.0850 (9)	0.0362 (5)	−0.0195 (7)	−0.0002 (5)	0.0044 (6)
C6	0.0464 (8)	0.0574 (9)	0.0407 (7)	0.0109 (7)	0.0005 (6)	−0.0038 (6)
C7	0.0467 (8)	0.0544 (8)	0.0463 (8)	0.0009 (7)	0.0005 (6)	0.0023 (7)
C8	0.0465 (7)	0.0513 (8)	0.0386 (6)	0.0071 (7)	0.0033 (6)	0.0078 (6)
C9	0.0462 (7)	0.0442 (7)	0.0362 (6)	0.0104 (6)	−0.0003 (6)	0.0037 (5)
C10	0.0537 (8)	0.0485 (8)	0.0424 (7)	0.0015 (7)	0.0029 (6)	0.0064 (6)
C11	0.0583 (9)	0.0585 (9)	0.0368 (6)	0.0065 (7)	0.0065 (7)	0.0046 (6)
C12	0.0500 (8)	0.0489 (8)	0.0394 (7)	0.0082 (7)	−0.0003 (6)	0.0032 (6)

Geometric parameters (Å, º)

O1—N1	1.3243 (16)	C4—C5	1.373 (2)
O1—O2	2.5796 (17)	C4—H4	0.9300
O2—HO2	0.90 (2)	N2—C6	1.368 (2)
N2—O3^i	2.975 (2)	O2—C12	1.320 (2)
N2—HN21	0.8600	O3—C12	1.2180 (17)
N2—O1^ii	3.095 (2)	C6—C11	1.390 (2)
N2—HN22	0.8600	C6—C7	1.405 (2)
C5—O3	3.273 (2)	C7—C8	1.374 (2)
C5—H5	0.9300	C7—H7	0.9300
N1—C1	1.3394 (19)	C8—C9	1.393 (2)
N1—C5	1.343 (2)	C8—H8	0.9300
C1—C2	1.367 (2)	C9—C10	1.398 (2)
C1—H1	0.9300	C9—C12	1.471 (2)
C2—C3	1.388 (2)	C10—C11	1.374 (2)
C2—H2	0.9300	C10—H10	0.9300
C3—C4	1.384 (2)	C11—H11	0.9300
C3—C3^iii	1.475 (3)
O1—N1—C1	119.23 (13)	C12—O2—HO2	108.8 (15)
O1—N1—C5	120.95 (13)	N2—C6—C11	121.24 (14)
O1—HO2—O2	157 (2)	N2—C6—C7	120.26 (16)
N2—HN21—O3^i	145.6	C11—C6—C7	118.49 (14)
N2—HN22—O1^ii	153.8	C8—C7—C6	120.34 (15)
C5—H5—O3	158.4	C8—C7—H7	119.8
C1—N1—C5	119.82 (13)	C6—C7—H7	119.8
N1—C1—C2	120.75 (15)	C7—C8—C9	121.19 (13)
N1—C1—H1	119.6	C7—C8—H8	119.4
C2—C1—H1	119.6	C9—C8—H8	119.4
C1—C2—C3	121.55 (14)	C8—C9—C10	118.23 (13)
C1—C2—H2	119.2	C8—C9—C12	119.44 (12)
C3—C2—H2	119.2	C10—C9—C12	122.30 (14)
C4—C3—C2	115.87 (13)	C11—C10—C9	120.87 (15)
C5—C4—C3	121.37 (15)	C11—C10—H10	119.6
C5—C4—H4	119.3	C9—C10—H10	119.6
C3—C4—H4	119.3	C10—C11—C6	120.88 (14)
N1—C5—C4	120.64 (14)	C10—C11—H11	119.6
N1—C5—H5	119.7	C6—C11—H11	119.6
C4—C5—H5	119.7	O3—C12—O2	122.43 (15)
C6—N2—HN21	120.0	O3—C12—C9	123.00 (15)
C6—N2—HN22	120.0	O2—C12—C9	114.53 (13)
HN21—N2—HN22	120.0
O1—N1—C1—C2	179.64 (17)	C7—C8—C9—C10	−0.3 (2)
C5—N1—C1—C2	0.4 (3)	C7—C8—C9—C12	177.87 (14)
N1—C1—C2—C3	0.1 (3)	C8—C9—C10—C11	0.3 (2)
C1—C2—C3—C4	−0.6 (2)	C12—C9—C10—C11	−177.81 (14)
C2—C3—C4—C5	0.8 (3)	C9—C10—C11—C6	0.0 (2)
O1—N1—C5—C4	−179.45 (18)	N2—C6—C11—C10	−179.78 (16)
C1—N1—C5—C4	−0.2 (3)	C7—C6—C11—C10	−0.2 (2)
C3—C4—C5—N1	−0.4 (3)	C8—C9—C12—O3	−7.4 (2)
N2—C6—C7—C8	179.79 (15)	C10—C9—C12—O3	170.65 (16)
C11—C6—C7—C8	0.2 (2)	C10—C9—C12—O2	−7.3 (2)
C6—C7—C8—C9	0.0 (2)	C8—C9—C12—O2	174.67 (14)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—HO2···O1	0.90 (2)	1.73 (2)	2.580 (2)	157 (2)
N2—HN21···O3^i	0.86	2.23	2.975 (2)	146
N2—HN22···O1^ii	0.86	2.30	3.095 (2)	154
C5—H5···O3	0.93	2.39	3.273 (2)	158

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