2,6-Di­phenyl­pyridine-4-carboxyl­ic acid

The distinctive feature of the crystal structure of 2,6-di­phenyl­pyridine-4-carboxyl­ic acid, C₁₈H₁₃NO₂, is the formation of intermolecular O—H...O hydrogen bonds that lead to the formation of centrosymmetric cyclic dimers with R(8) topology. Molecules related by translation along the b axis exhibit strong π–π stacking of aromatic rings, with an average interplanar distance of 3.3 Å.

S1. Comment

The most common packing motif of carboxylic acids is based on the formation of cyclic dimers through a pair of O—H···O bonds (Leiserowitz, 1976). By contrast, the solid state chemistry of pyridinecarboxylic acids is dominated by the formation of an intermolecular O—H···N hydrogen-bond between the carboxylic group and the pyridine nitrogen atom of a second molecule (Takusagawa & Shimada, 1976; Wright & King, 1953). The latter H-bonding interaction can be described more accurately as occurring via O—H···N or ⁺N—H···O^- bonds depending on the tautomeric form present. Similar arguments also apply to other heterocyclic aromatic carboxylic acids such as the pyrazinic acid (Takusagawa et al., 1974) and the quinoline-4-carboxylic acid (Dobson & Gerkin, 1998). The directional nature of the O—H···N bonding interaction for the isonicotinic acid has been exploited in the promotion of highly oriented structures (O'Shea et al., 2001). On the other hand, when carboxylic groups occupy both α and α' positions of the pyridine ring - as in the dipicolinic acid - the nitrogen atom is not involved in head-to-tail interactions of the type described, although O—H···N hydrogen-bonds with a cocrystallized water molecule are still present (Takusagawa et al., 1973).

The molecular structure of (I) is shown in Figure 1. Geometric parameters are normal (Table 1) and compare well with those of other 2,6-diphenyl-pyridines (Krygowski et al., 1994; Silva et al., 1997). The whole molecule is nearly planar, as clearly shown by the values of the torsion angles reported in Table 1. Dihedral angles between the best-fit plane of the pyridine and those of the phenyl substituents are 8.7 (1)° (ring atoms C8,···,C13) and 9.8 (1)° (ring atoms C14,···,C19), respectively.

The supramolecular structure of (I) can be described in terms of π-π interactions and intermolecular H-bonding (Table 2). In the crystal packing the molecules are stacked along the b axis (Figure 2). The shortest interplanar distance of 2.919 (2) Å is found between the phenyl ring C14,···C19 and its translation-related one. The stacks are organized in a pseudo-herringbone fashion since the π-H interactions do not seem to be dominant like in a classical herringbone stacking mode (Gavezzotti & Desiraju, 1988; Andre et al., 1997). The dominant supramolecular interaction is the couple of O—H···O hydrogen bonds between centrosymmetric carboxylic acid groups (Figure 3). The corresponding graph-set is therefore R₂²(8) (Etter et al., 1990), which is typical for carboxyl dimers. In addition, a second motif with graph-set R₄⁶(44) can be identify in the crystal packing when weaker hydrogen bonds of the C—H···O type are considered (Fig. 3).

S2. Experimental

The title compound was prepared in one step from 3-benzoylacrilic acid and N-phenacylpyridinium bromide in the presence of excess ammonium acetate (Blumbergs et al., 1972). The compound was recrystallized from hot acetic acid affording pale yellow crystals.

Computing details

Data collection: XPREP (Bruker, 1997); cell refinement: XPREP (Bruker, 1997); data reduction: XPREP (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Bruker, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

	Fig. 1. Molecular structure of (I) showing the atom labelling scheme and displacement ellipsoids drawn at the 50% probability level.
	Fig. 2. Crystal packing of (I) viewed down the b axis.
	Fig. 3. Partial view of the crystal structure of (I) showing the formation of ring motifs with graph-set R2^2(8) that further interact through lateral C—H···O interactions to afford larger rings with graph-set R4^6(44).

(I)

Crystal data

C18H13NO2	F(000) = 576
Mr = 275.29	Dx = 1.32 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 16.524 (4) Å	Cell parameters from 25 reflections
b = 5.2898 (9) Å	θ = 8.0–12.9°
c = 17.021 (3) Å	µ = 0.09 mm^−1
β = 111.229 (17)°	T = 293 K
V = 1386.8 (5) Å^3	Block, pale yellow
Z = 4	0.23 × 0.20 × 0.17 mm

Data collection

Siemens R3m/V diffractometer	Rint = 0.069
Radiation source: X-ray tube	θmax = 25.1°, θmin = 1.5°
Graphite monochromator	h = 0→19
θ/2θ scans	k = 0→6
2559 measured reflections	l = −20→18
2469 independent reflections	2 standard reflections every 48 min
980 reflections with I > 2σ(I)	intensity decay: no decay, variation 0.5%

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F^2 > 2σ(F^2)] = 0.045	w = 1/[σ^2(Fo^2) + (0.025P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.089	(Δ/σ)max < 0.001
S = 0.87	Δρmax = 0.13 e Å^−3
2469 reflections	Δρmin = −0.13 e Å^−3
190 parameters

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

	x	y	z	Uiso*/Ueq
N1	0.92467 (13)	0.1108 (4)	0.69830 (13)	0.0515 (6)
O1	1.05832 (11)	0.7793 (4)	0.57999 (10)	0.0709 (6)
H1	1.0619	0.9040	0.5528	0.106*
O2	0.91707 (11)	0.8373 (4)	0.50817 (11)	0.0674 (6)
C2	0.85978 (16)	0.2316 (5)	0.63842 (16)	0.0483 (7)
C3	0.87627 (16)	0.4328 (5)	0.59355 (16)	0.0518 (8)
H3	0.8307	0.5145	0.5523	0.062*
C4	0.96062 (17)	0.5099 (5)	0.61078 (16)	0.0481 (7)
C5	1.02650 (16)	0.3905 (5)	0.67265 (16)	0.0542 (8)
H5	1.0836	0.4438	0.6863	0.065*
C6	1.00715 (16)	0.1875 (5)	0.71508 (16)	0.0513 (8)
C7	0.97728 (18)	0.7241 (5)	0.56290 (17)	0.0527 (8)
C8	1.07541 (17)	0.0392 (5)	0.78092 (16)	0.0518 (7)
C9	1.16336 (18)	0.0702 (7)	0.79678 (18)	0.0833 (11)
H9	1.1815	0.1914	0.7671	0.100*
C10	1.22390 (19)	−0.0766 (7)	0.8559 (2)	0.0853 (11)
H10	1.2825	−0.0517	0.8658	0.102*
C11	1.20051 (19)	−0.2564 (6)	0.90019 (17)	0.0743 (10)
H11	1.2422	−0.3560	0.9394	0.089*
C12	1.11401 (19)	−0.2885 (7)	0.88584 (19)	0.0910 (11)
H12	1.0964	−0.4100	0.9157	0.109*
C13	1.05300 (18)	−0.1394 (6)	0.8267 (2)	0.0764 (10)
H13	0.9946	−0.1623	0.8181	0.092*
C14	0.77008 (16)	0.1425 (5)	0.62523 (16)	0.0490 (7)
C15	0.75731 (16)	−0.0738 (6)	0.66479 (16)	0.0583 (8)
H15	0.8051	−0.1684	0.6974	0.070*
C16	0.67528 (18)	−0.1521 (6)	0.65700 (17)	0.0688 (9)
H16	0.6680	−0.2968	0.6848	0.083*
C17	0.60398 (19)	−0.0149 (7)	0.60776 (19)	0.0730 (10)
H17	0.5484	−0.0671	0.6022	0.088*
C18	0.61493 (18)	0.1974 (7)	0.56717 (19)	0.0743 (9)
H18	0.5668	0.2902	0.5341	0.089*
C19	0.69789 (17)	0.2752 (6)	0.57512 (17)	0.0639 (8)
H19	0.7048	0.4181	0.5464	0.077*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0433 (13)	0.0622 (17)	0.0502 (15)	0.0008 (13)	0.0184 (11)	0.0015 (13)
O1	0.0584 (12)	0.0761 (15)	0.0817 (14)	−0.0043 (12)	0.0294 (10)	0.0206 (13)
O2	0.0562 (12)	0.0744 (15)	0.0683 (14)	−0.0015 (11)	0.0185 (10)	0.0202 (12)
C2	0.0446 (16)	0.050 (2)	0.0515 (18)	−0.0025 (15)	0.0190 (15)	−0.0066 (16)
C3	0.0473 (17)	0.054 (2)	0.0554 (19)	0.0028 (15)	0.0194 (14)	0.0021 (16)
C4	0.0496 (17)	0.0456 (19)	0.0532 (19)	−0.0039 (15)	0.0237 (15)	−0.0001 (16)
C5	0.0451 (16)	0.062 (2)	0.0576 (19)	−0.0012 (16)	0.0203 (15)	0.0026 (17)
C6	0.0451 (17)	0.056 (2)	0.0532 (19)	−0.0005 (15)	0.0179 (15)	0.0026 (16)
C7	0.0495 (17)	0.057 (2)	0.0544 (19)	−0.0057 (17)	0.0225 (15)	−0.0024 (18)
C8	0.0503 (18)	0.056 (2)	0.0505 (18)	−0.0026 (16)	0.0203 (15)	0.0002 (16)
C9	0.0500 (18)	0.117 (3)	0.084 (3)	0.004 (2)	0.0257 (18)	0.037 (2)
C10	0.0491 (18)	0.122 (3)	0.083 (3)	0.014 (2)	0.0212 (18)	0.028 (2)
C11	0.062 (2)	0.084 (3)	0.067 (2)	0.009 (2)	0.0097 (17)	0.010 (2)
C12	0.061 (2)	0.107 (3)	0.090 (3)	−0.008 (2)	0.0096 (18)	0.041 (2)
C13	0.0474 (18)	0.092 (3)	0.080 (2)	−0.0061 (19)	0.0124 (17)	0.027 (2)
C14	0.0439 (16)	0.054 (2)	0.0500 (18)	−0.0015 (15)	0.0182 (14)	−0.0049 (16)
C15	0.0478 (18)	0.067 (2)	0.061 (2)	−0.0035 (16)	0.0209 (15)	0.0004 (18)
C16	0.0587 (19)	0.082 (2)	0.069 (2)	−0.014 (2)	0.0260 (17)	−0.0033 (19)
C17	0.054 (2)	0.086 (3)	0.083 (3)	−0.010 (2)	0.0297 (19)	−0.015 (2)
C18	0.0463 (18)	0.077 (3)	0.094 (3)	0.0000 (18)	0.0182 (17)	−0.004 (2)
C19	0.0524 (17)	0.067 (2)	0.070 (2)	−0.0020 (18)	0.0191 (16)	0.0050 (18)

Geometric parameters (Å, º)

N1—C2	1.343 (3)	C10—C11	1.354 (4)
N1—C6	1.350 (3)	C10—H10	0.9300
O1—C7	1.297 (3)	C11—C12	1.371 (3)
O1—H1	0.8200	C11—H11	0.9300
O2—C7	1.243 (3)	C12—C13	1.384 (4)
C2—C3	1.393 (3)	C12—H12	0.9300
C2—C14	1.493 (3)	C13—H13	0.9300
C3—C4	1.378 (3)	C14—C19	1.381 (3)
C3—H3	0.9300	C14—C15	1.382 (3)
C4—C5	1.365 (3)	C15—C16	1.377 (3)
C4—C7	1.478 (3)	C15—H15	0.9300
C5—C6	1.394 (3)	C16—C17	1.379 (4)
C5—H5	0.9300	C16—H16	0.9300
C6—C8	1.493 (3)	C17—C18	1.364 (4)
C8—C13	1.359 (3)	C17—H17	0.9300
C8—C9	1.389 (3)	C18—C19	1.390 (3)
C9—C10	1.374 (4)	C18—H18	0.9300
C9—H9	0.9300	C19—H19	0.9300
C2—N1—C6	119.0 (2)	C9—C10—H10	119.1
C7—O1—H1	109.5	C10—C11—C12	118.5 (3)
N1—C2—C3	121.2 (2)	C10—C11—H11	120.7
N1—C2—C14	116.1 (3)	C12—C11—H11	120.7
C3—C2—C14	122.6 (3)	C11—C12—C13	119.8 (3)
C4—C3—C2	119.5 (3)	C11—C12—H12	120.1
C4—C3—H3	120.2	C13—C12—H12	120.1
C2—C3—H3	120.2	C8—C13—C12	122.4 (3)
C5—C4—C3	119.3 (3)	C8—C13—H13	118.8
C5—C4—C7	121.6 (3)	C12—C13—H13	118.8
C3—C4—C7	119.0 (3)	C19—C14—C15	118.1 (3)
C4—C5—C6	119.2 (2)	C19—C14—C2	121.4 (3)
C4—C5—H5	120.4	C15—C14—C2	120.4 (3)
C6—C5—H5	120.4	C16—C15—C14	121.4 (3)
N1—C6—C5	121.7 (2)	C16—C15—H15	119.3
N1—C6—C8	115.6 (3)	C14—C15—H15	119.3
C5—C6—C8	122.8 (2)	C15—C16—C17	119.6 (3)
O2—C7—O1	122.8 (3)	C15—C16—H16	120.2
O2—C7—C4	121.6 (2)	C17—C16—H16	120.2
O1—C7—C4	115.6 (3)	C18—C17—C16	120.0 (3)
C13—C8—C9	117.0 (3)	C18—C17—H17	120.0
C13—C8—C6	120.5 (3)	C16—C17—H17	120.0
C9—C8—C6	122.5 (3)	C17—C18—C19	120.1 (3)
C10—C9—C8	120.6 (3)	C17—C18—H18	120.0
C10—C9—H9	119.7	C19—C18—H18	120.0
C8—C9—H9	119.7	C14—C19—C18	120.7 (3)
C11—C10—C9	121.7 (3)	C14—C19—H19	119.6
C11—C10—H10	119.1	C18—C19—H19	119.6
C6—N1—C2—C3	0.2 (4)	C13—C8—C9—C10	0.5 (5)
C6—N1—C2—C14	−178.0 (2)	C6—C8—C9—C10	−177.7 (3)
N1—C2—C3—C4	0.0 (4)	C8—C9—C10—C11	0.5 (5)
C14—C2—C3—C4	178.1 (2)	C9—C10—C11—C12	−0.9 (5)
C2—C3—C4—C5	−1.2 (4)	C10—C11—C12—C13	0.4 (5)
C2—C3—C4—C7	−179.8 (2)	C9—C8—C13—C12	−1.0 (5)
C3—C4—C5—C6	2.1 (4)	C6—C8—C13—C12	177.2 (3)
C7—C4—C5—C6	−179.2 (2)	C11—C12—C13—C8	0.6 (5)
C2—N1—C6—C5	0.8 (4)	N1—C2—C14—C19	170.0 (2)
C2—N1—C6—C8	−178.5 (2)	C3—C2—C14—C19	−8.2 (4)
C4—C5—C6—N1	−2.0 (4)	N1—C2—C14—C15	−8.6 (3)
C4—C5—C6—C8	177.3 (2)	C3—C2—C14—C15	173.3 (2)
C5—C4—C7—O2	−178.0 (3)	C19—C14—C15—C16	−2.0 (4)
C3—C4—C7—O2	0.7 (4)	C2—C14—C15—C16	176.6 (2)
C5—C4—C7—O1	4.1 (4)	C14—C15—C16—C17	1.0 (4)
C3—C4—C7—O1	−177.2 (2)	C15—C16—C17—C18	−0.1 (5)
N1—C6—C8—C13	−7.6 (4)	C16—C17—C18—C19	0.2 (5)
C5—C6—C8—C13	173.0 (3)	C15—C14—C19—C18	2.1 (4)
N1—C6—C8—C9	170.5 (3)	C2—C14—C19—C18	−176.4 (2)
C5—C6—C8—C9	−8.9 (4)	C17—C18—C19—C14	−1.3 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O2^i	0.82	1.83	2.640 (3)	172
C11—H11···O2^ii	0.93	2.70	3.406 (3)	134

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