Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270105039077/gd1421sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270105039077/gd1421Isup2.hkl |
CCDC reference: 296346
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).
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 Uiso(H) = 1.2Ueq(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 Uiso(H) = 1.5Ueq(O).
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.
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.
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) Å3 | 0.28 × 0.18 × 0.10 mm |
Z = 4 |
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 on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.039 | H-atom parameters constrained |
wR(F2) = 0.111 | w = 1/[σ2(Fo2) + (0.0658P)2] where P = (Fo2 + 2Fc2)/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+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0014 (4) |
C14H10O4·C12H8N4O | V = 2166.1 (7) Å3 |
Mr = 466.44 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 21.131 (4) Å | µ = 0.10 mm−1 |
b = 6.8459 (11) Å | T = 293 K |
c = 15.376 (3) Å | 0.28 × 0.18 × 0.10 mm |
β = 103.135 (2)° |
Bruker SMART APEX-II CCD area-detector diffractometer | 1906 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 1256 reflections with I > 2σ(I) |
Tmin = 0.795, Tmax = 0.990 | Rint = 0.025 |
5668 measured reflections |
R[F2 > 2σ(F2)] = 0.039 | 0 restraints |
wR(F2) = 0.111 | H-atom parameters constrained |
S = 0.98 | Δρmax = 0.17 e Å−3 |
1906 reflections | Δρmin = −0.16 e Å−3 |
161 parameters |
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. |
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* |
U11 | U22 | U33 | U12 | U13 | U23 | |
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) |
O1—C6i | 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—N2i | 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—C11ii | 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 |
C6i—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—N2i | 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—C11ii | 121.82 (19) |
C3—C4—H4 | 120.6 | C10—C11—C11ii | 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) |
N2i—N2—C6—O1 | −0.1 (2) | C9—C10—C11—C12 | −1.7 (3) |
N2i—N2—C6—C5 | 179.50 (17) | C9—C10—C11—C11ii | 178.47 (18) |
C6i—O1—C6—N2 | 0.04 (9) | C10—C11—C12—C13 | 0.5 (3) |
C6i—O1—C6—C5 | −179.59 (17) | C11ii—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. |
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···O3iii | 0.93 | 2.29 | 3.153 (2) | 155 |
Symmetry code: (iii) x, y−1, z. |
Experimental details
Crystal data | |
Chemical formula | C14H10O4·C12H8N4O |
Mr | 466.44 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 293 |
a, b, c (Å) | 21.131 (4), 6.8459 (11), 15.376 (3) |
β (°) | 103.135 (2) |
V (Å3) | 2166.1 (7) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.28 × 0.18 × 0.10 |
Data collection | |
Diffractometer | Bruker SMART APEX-II CCD area-detector |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.795, 0.990 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5668, 1906, 1256 |
Rint | 0.025 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.039, 0.111, 0.98 |
No. of reflections | 1906 |
No. of parameters | 161 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.17, −0.16 |
Computer programs: APEX2 (Bruker, 2003), APEX2 and SAINT (Bruker, 2001), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 2001) and DIAMOND (Brandenburg & Berndt, 1999), SHELXTL.
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···O3i | 0.93 | 2.29 | 3.153 (2) | 155 |
Symmetry code: (i) x, y−1, z. |
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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.