Hydrogen-bonded sheets in the 1:1 cocrystal of biphenyl-4,4′-dicarboxylic acid with 2,5-di-4-pyrid­yl-1,3,4-oxadiazole

The combination of biphenyl-4,4′-dicarboxylic acid (H₂bpa) and the bent dipyridyl base 2,5-di-4-pyridyl-1,3,4-oxadiazole (4-bpo) in a 1:1 molar ratio leads to the formation of the mol­ecular cocrystal (H₂bpa)·(4-bpo) or C₁₄H₁₀O₄·C₁₂H₈N₄O. The asymmetric unit contains one-half of an H₂bpa unit lying across a centre of inversion and one-half of a 4-bpo mol­ecule lying across a twofold rotation axis. Inter­molecular O—H...N inter­actions connect the acid and base mol­ecules to form a one-dimensional zigzag chain. Through further weak C—H...O hydrogen bonds between adjacent chains, a two-dimensional sheet-like supramolecular network is afforded. As an extended analogue of terephthalic acid (H₂tp), the backbone geometry of H₂bpa has an evident influence on the hydrogen-bonding pattern of the title cocrystal compared with that of (H₂tp)·(4-bpo).

S1. Comment

Organic crystal engineering of acid–base binary complexes assembled into predictable supramolecular architectures is a subject of continuing interest, which has focused on selective and directional hydrogen bonds in both natural and artificial systems (Desiraju, 1989; Steiner, 2002). One of the important approaches is to utilize the self-organization of small organic molecules with classical O—H···O and O—H···N hydrogen bonding and other weak hydrogen bonds, such as C—H···O, to construct infinite one-, two- or three-dimensional networks in crystalline solids (Ma & Coppens, 2003; Aakeröy & Salmon, 2005). In this context, not only strong hydrogen-bonding interactions but also weak hydrogen bonds need to be considered carefully because they can affect the crystal packing in unpredictable ways (Desiraju, 2002).

2,5-Bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo), a bent dipyridyl analogue, has abundant heteroatoms with free electron pairs that could be considered as multiple hydrogen-bonding sites. Recently, it has been successfully used to create a series of hydrogen-bonded co-crystals displaying one-dimensional tape, two-dimensional layer, three-dimensional net and helical style frameworks, with aromatic di- or polycarboxylic acids (Du et al., 2005a,b) such as terephthalic acid and trimesic acid. 4,4'-Biphenyldicarboxylic acid (H₂bpa), as a long rod-shaped building block, has received considerable attention in the design of porous metal–organic frameworks (MOFs) with adsorption properties (Rosi et al., 2005). Such a building block attracts our interest for its similar geometry but different length compared with terephthalic acid, which can form strong and directional noncovalent interactions. Also, it is rarely utilized in co-crystallization with organic bases and always forms charge-transfer compounds and not molecular co-crystals (Felix et al., 1997; Xue & Mak, 2000). Therefore, the combination of H₂bpa with 4-bpo may be expected to give diverse hydrogen-bonding modes and an interesting network. Here, we report the structure of the title co-crystal, [(H₂bpa).(4-bpo)], (I), which has a two-dimensional sheet hydrogen-bonded network.

X-ray single-crystal diffraction analysis shows that H₂bpa co-crystallizes with 4-bpo in a 1:1 molar ratio, producing a binary molecular crystal, [(H₂bpa).(4-bpo)], (I), as depicted in Fig. 1. Bond lengths and angles (see archived CIF) agree with accepted values (Reference for standard values?). The asymmetric unit of (I) contains half of a centrosymmetric H₂bpa subunit with the inversion centre (1/2, 1, 0) at the midpoint of the C11—C11A bond, and half of a crystallographic twofold symmetric 4-bpo molecule, in which the twofold rotation axis passes through atom O1 and the centre of the N2—N2B bond along (0, y, 1/4). The mean planes of the two components including all non-H atoms are inclined to each other with a dihedral angle of 9.4 (3)°. The terminal pyridyl rings in 4-bpo form dihedral angles of 1.0 (2)° with the central oxadiazole plane, and a dihedral angle of 1.9 (2)° with each other. For the H₂bpa component, the two terminal carboxylic acid groups adopt a trans-coplanar conformation in relation to the central biphenyl moiety, due to its symmetry.

The hydrogen-bond geometries and symmetry codes are listed in Table 1. From Fig. 2, we can clearly observe that the base and acid components are connected through the O2—H2A···N1 interactions, producing a one-dimensional zigzag chain running along the [201] direction. Adjacent chains arrayed in a parallel mode along the crystallographic [010] direction are further linked by weak C3—H3···O3 hydrogen bonds to form a two-dimensional planar network. These (102) sheets are packed in a parallel and somewhat offset manner. There are no further hydrogen-bonding interactions or aromatic stacking between adjacent layers and five such sheets pass through the unit cell. Examination of this structure with PLATON (Spek, 2003) showed that there were no solvent-accessible voids in the crystal lattice.

H₂bpa has a similar carboxylate geometry compared with terephthalic acid (H₂tp) and could act as a longer rod-like building block with a separation of ca12 Å (the corresponding value for H₂tp is ca 8 Å). In contrast with the structure of the co-crystal based on 4-bpo and H₂tp (Du et al., 2005a), the characteristic hydrogen-bonding motif and further crystal packing of compound (I) are as follows. The length of the acid component H₂bpa, as the only variable factor compared with H₂tp, may adjust the crystal structure into a two-dimensional planar network in which the acid–base chains are arranged in a parallel fashion, while for [(H₂tp).(4-bpo)], H₂tp and 4-bpo are arrayed alternately on either side of the to-dimensional acid–base plane. The low slope between the acid and base molecules and the large separation between the adjacent layers in (I) result in an absence of interlayer hydrogen-bonding interactions or aromatic stacking, while for [(H₂tp).(4-bpo)], the two-dimensional layers are further extended to form a three-dimensional net via interlayer C—H···O interactions.

In conclusion, this work indicates that H₂bpa is also a good participant in hydrogen-bonding networks for the formation of acid–base molecular co-crystals and, notably, compound (I) represents the first example of H₂bpa as a neutral component in acid–base adducts.

S2. Experimental

A dimethylformamide solution (10 ml) of H₂bpa (24.2 mg, 0.1 mmol) was carefully layered onto a solution of 4-bpo (22.4 mg, 0.1 mmol) in CHCl₃ (6 ml) in a straight glass tube. Colourless block crystals of (I) were obtained on the tube wall over a period of 3 weeks in 85% yield. Analysis, calculated for C₂₆H₁₈N₄O₅: C 66.95, H 3.89, N 12.01%; found: C 66.91, H 3.74, N 12.31%. Spectroscopic analysis: IR (KBr pellet, ν, cm^-1): 3434 (b), 2973 (s), 2938 (s), 2802 (m), 2739 (s), 2677 (vs), 2601 (m), 2569 (m), 2528 (m), 2396 (w), 2354 (w), 1763 (w), 1606 (w), 1562 (w), 1474 (s), 1393 (vs), 1170 (m), 1075 (w), 1036 (m), 847 (w), 827 (m), 804 (w), 714 (w), 460 (w).

S3. Refinement

There was no evidence of crystal decay during data collection. The space group C2/c was uniquely assigned from the systematic absences. All H atoms were visible in difference maps. C-bound H atoms were placed in calculated positions, with C—H distances of 0.93 Å, and refined as riding atoms, with U_iso(H) = 1.2U_eq(C). O-bound carboxyl H atoms were refined as rigid groups, with O—H distances of 0.82 Å, and allowed to rotate but not tip, with U_iso(H) = 1.5U_eq(O).

Computing details

Data collection: APEX2 (Bruker, 2003); cell refinement: APEX2 and SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2001) and DIAMOND (Brandenburg & Berndt, 1999); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The molecular structure of (I), drawn with 30% probability ellipsoids [Symmetry codes: (A) 1 - x, 2 - y, -z; (B) -x, y, 1/2 - z.]
	Fig. 2. A perspective view of the two-dimensional hydrogen-bonded sheet along (102). Hydrogen bonds are indicated by dashed lines. The base molecules are indicated by the unit cell. H atoms not involved in the hydrogen bonds shown have been omitted. [Symmetry codes: (A) x, -1 + y, z; (B) -x, y, 1/2 - z; (C) -1 + x, 2 - y, 1/2 + z; (D) -1 - x, 2 - y, 1 - z; (E) 1 - x, 2 - y, -z.]

4,4'-biphenyldicarboxylic acid–2,5-bis(4-pyridyl)-1,3,4-oxadiazole (1/1)

Crystal data

C14H10O4·C12H8N4O	F(000) = 968
Mr = 466.44	Dx = 1.430 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 978 reflections
a = 21.131 (4) Å	θ = 3.1–21.9°
b = 6.8459 (11) Å	µ = 0.10 mm^−1
c = 15.376 (3) Å	T = 293 K
β = 103.135 (2)°	Block, colourless
V = 2166.1 (7) Å^3	0.28 × 0.18 × 0.10 mm
Z = 4

Data collection

Bruker SMART APEX-II CCD area-detector diffractometer	1906 independent reflections
Radiation source: fine-focus sealed tube	1256 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.025
φ and ω scans	θmax = 25.0°, θmin = 2.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −24→24
Tmin = 0.795, Tmax = 0.990	k = −7→8
5668 measured reflections	l = −17→18

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.039	H-atom parameters constrained
wR(F^2) = 0.111	w = 1/[σ^2(Fo^2) + (0.0658P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.98	(Δ/σ)max < 0.001
1906 reflections	Δρmax = 0.17 e Å^−3
161 parameters	Δρmin = −0.16 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0014 (4)

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.

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
O1	0.0000	0.2611 (2)	0.2500	0.0443 (4)
O2	0.30793 (5)	0.49216 (17)	0.08614 (9)	0.0615 (4)
H2A	0.2766	0.4507	0.1037	0.092*
O3	0.26823 (5)	0.77931 (17)	0.11535 (8)	0.0599 (4)
N1	0.20794 (6)	0.3562 (2)	0.14557 (10)	0.0535 (4)
N2	0.02878 (7)	−0.0437 (2)	0.23506 (11)	0.0609 (4)
C1	0.11067 (7)	0.4143 (2)	0.19541 (10)	0.0480 (5)
H1	0.0818	0.5037	0.2106	0.058*
C2	0.16522 (8)	0.4765 (3)	0.16876 (12)	0.0537 (5)
H2	0.1726	0.6102	0.1669	0.064*
C3	0.19701 (8)	0.1671 (3)	0.14924 (12)	0.0593 (5)
H3	0.2264	0.0812	0.1329	0.071*
C4	0.14419 (8)	0.0904 (2)	0.17612 (12)	0.0558 (5)
H4	0.1386	−0.0440	0.1787	0.067*
C5	0.09982 (7)	0.2170 (2)	0.19909 (10)	0.0435 (4)
C6	0.04364 (7)	0.1373 (3)	0.22744 (10)	0.0448 (4)
C7	0.30894 (7)	0.6832 (3)	0.09055 (10)	0.0454 (4)
C8	0.36560 (7)	0.7745 (2)	0.06369 (10)	0.0425 (4)
C9	0.37652 (8)	0.9713 (3)	0.07459 (12)	0.0577 (5)
H9	0.3480	1.0474	0.0981	0.069*
C10	0.42903 (8)	1.0579 (3)	0.05131 (12)	0.0599 (5)
H10	0.4358	1.1911	0.0612	0.072*
C11	0.47218 (7)	0.9529 (2)	0.01357 (10)	0.0415 (4)
C12	0.46031 (8)	0.7547 (2)	0.00286 (13)	0.0546 (5)
H12	0.4882	0.6783	−0.0218	0.065*
C13	0.40856 (7)	0.6672 (3)	0.02756 (12)	0.0542 (5)
H13	0.4024	0.5332	0.0198	0.065*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0387 (9)	0.0454 (10)	0.0516 (10)	0.000	0.0165 (7)	0.000
O2	0.0556 (8)	0.0467 (8)	0.0926 (10)	−0.0040 (6)	0.0384 (7)	−0.0005 (6)
O3	0.0539 (8)	0.0529 (8)	0.0819 (10)	0.0033 (6)	0.0341 (7)	0.0000 (6)
N1	0.0464 (8)	0.0490 (10)	0.0701 (10)	0.0006 (7)	0.0241 (7)	0.0011 (7)
N2	0.0533 (9)	0.0512 (9)	0.0876 (12)	0.0016 (7)	0.0357 (8)	−0.0006 (8)
C1	0.0435 (10)	0.0482 (11)	0.0552 (11)	0.0094 (8)	0.0174 (8)	0.0018 (8)
C2	0.0503 (10)	0.0439 (10)	0.0707 (12)	0.0028 (8)	0.0219 (9)	0.0036 (9)
C3	0.0499 (10)	0.0510 (11)	0.0849 (14)	0.0047 (9)	0.0319 (9)	−0.0076 (10)
C4	0.0536 (11)	0.0439 (11)	0.0762 (13)	−0.0009 (8)	0.0280 (9)	−0.0053 (9)
C5	0.0391 (9)	0.0472 (11)	0.0452 (10)	0.0006 (7)	0.0117 (7)	−0.0018 (8)
C6	0.0400 (9)	0.0477 (11)	0.0497 (11)	0.0024 (8)	0.0164 (8)	−0.0014 (8)
C7	0.0444 (10)	0.0466 (11)	0.0465 (10)	0.0022 (8)	0.0130 (8)	0.0025 (8)
C8	0.0408 (9)	0.0408 (10)	0.0457 (10)	0.0000 (7)	0.0095 (7)	0.0046 (7)
C9	0.0610 (11)	0.0461 (11)	0.0782 (13)	0.0044 (8)	0.0415 (10)	−0.0005 (9)
C10	0.0711 (12)	0.0364 (10)	0.0839 (14)	−0.0007 (8)	0.0423 (11)	0.0004 (9)
C11	0.0429 (9)	0.0380 (9)	0.0442 (9)	0.0029 (7)	0.0115 (7)	0.0035 (7)
C12	0.0451 (10)	0.0417 (11)	0.0844 (13)	0.0002 (8)	0.0304 (9)	−0.0078 (9)
C13	0.0502 (10)	0.0368 (10)	0.0794 (13)	−0.0038 (8)	0.0232 (9)	−0.0069 (9)

Geometric parameters (Å, º)

O1—C6^i	1.3546 (17)	C4—C5	1.380 (2)
O1—C6	1.3546 (17)	C4—H4	0.9300
O2—C7	1.3095 (18)	C5—C6	1.460 (2)
O2—H2A	0.8200	C7—C8	1.490 (2)
O3—C7	1.2115 (18)	C8—C9	1.370 (2)
N1—C3	1.319 (2)	C8—C13	1.379 (2)
N1—C2	1.329 (2)	C9—C10	1.375 (2)
N2—C6	1.290 (2)	C9—H9	0.9300
N2—N2^i	1.395 (3)	C10—C11	1.387 (2)
C1—C5	1.374 (2)	C10—H10	0.9300
C1—C2	1.376 (2)	C11—C12	1.383 (2)
C1—H1	0.9300	C11—C11^ii	1.481 (3)
C2—H2	0.9300	C12—C13	1.374 (2)
C3—C4	1.379 (2)	C12—H12	0.9300
C3—H3	0.9300	C13—H13	0.9300
C6^i—O1—C6	102.50 (17)	O3—C7—O2	123.66 (15)
C7—O2—H2A	109.5	O3—C7—C8	122.16 (16)
C3—N1—C2	117.45 (15)	O2—C7—C8	114.17 (14)
C6—N2—N2^i	106.17 (9)	C9—C8—C13	117.72 (15)
C5—C1—C2	118.41 (16)	C9—C8—C7	120.14 (15)
C5—C1—H1	120.8	C13—C8—C7	122.14 (15)
C2—C1—H1	120.8	C8—C9—C10	121.02 (16)
N1—C2—C1	123.64 (17)	C8—C9—H9	119.5
N1—C2—H2	118.2	C10—C9—H9	119.5
C1—C2—H2	118.2	C9—C10—C11	122.08 (17)
N1—C3—C4	123.23 (16)	C9—C10—H10	119.0
N1—C3—H3	118.4	C11—C10—H10	119.0
C4—C3—H3	118.4	C12—C11—C10	116.07 (15)
C3—C4—C5	118.76 (16)	C12—C11—C11^ii	121.82 (19)
C3—C4—H4	120.6	C10—C11—C11^ii	122.11 (18)
C5—C4—H4	120.6	C13—C12—C11	121.94 (16)
C1—C5—C4	118.51 (15)	C13—C12—H12	119.0
C1—C5—C6	122.30 (15)	C11—C12—H12	119.0
C4—C5—C6	119.19 (15)	C12—C13—C8	121.14 (16)
N2—C6—O1	112.58 (14)	C12—C13—H13	119.4
N2—C6—C5	128.11 (15)	C8—C13—H13	119.4
O1—C6—C5	119.31 (15)
C3—N1—C2—C1	−0.5 (3)	C4—C5—C6—O1	−179.98 (13)
C5—C1—C2—N1	0.6 (3)	O3—C7—C8—C9	6.3 (2)
C2—N1—C3—C4	−0.3 (3)	O2—C7—C8—C9	−172.75 (15)
N1—C3—C4—C5	1.1 (3)	O3—C7—C8—C13	−173.76 (15)
C2—C1—C5—C4	0.2 (2)	O2—C7—C8—C13	7.2 (2)
C2—C1—C5—C6	179.36 (15)	C13—C8—C9—C10	−0.8 (3)
C3—C4—C5—C1	−0.9 (3)	C7—C8—C9—C10	179.13 (16)
C3—C4—C5—C6	179.86 (15)	C8—C9—C10—C11	1.9 (3)
N2^i—N2—C6—O1	−0.1 (2)	C9—C10—C11—C12	−1.7 (3)
N2^i—N2—C6—C5	179.50 (17)	C9—C10—C11—C11^ii	178.47 (18)
C6^i—O1—C6—N2	0.04 (9)	C10—C11—C12—C13	0.5 (3)
C6^i—O1—C6—C5	−179.59 (17)	C11^ii—C11—C12—C13	−179.68 (18)
C1—C5—C6—N2	−178.75 (17)	C11—C12—C13—C8	0.5 (3)
C4—C5—C6—N2	0.5 (3)	C9—C8—C13—C12	−0.4 (3)
C1—C5—C6—O1	0.8 (2)	C7—C8—C13—C12	179.68 (15)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2A···N1	0.82	1.83	2.654 (2)	179
C3—H3···O3^iii	0.93	2.29	3.153 (2)	155

Symmetry code: (iii) x, y−1, z.