organic compounds
2-[2,6-Bis(pyrazin-2-yl)pyridin-4-yl]benzoic acid
aSchool of Chemistry and Environment, South China Normal University, Guangzhou 510006, People's Republic of China
*Correspondence e-mail: wujzh@scnu.edu.cn
In the title compound, C20H13N5O2, the two pyrazine rings are nearly coplanar with the central pyridine ring, forming dihedral angles of 2.21 (9) and 4.57 (9)°. In contrast, the strong caused by the ortho-carboxyl group on the phenyl ring makes this ring rotate out of the attached pyridine ring plane by 52.60 (9)°. The carboxyl group is twisted from the phenyl ring by 22.6 (1)°. In the crystal, aromatic π–π stacking interactions [centroid–centroid distances = 3.9186 (4) and 3.9794 (5) Å] occur between the antiparallel molecules, generating infinite chains along [100]. O—H⋯O hydrogen bonds connect the chains, leading to the formation of a two-dimensional supramolecular network parallel to (010). Intermolecular C—H⋯N hydrogen bonds are also observed.
CCDC reference: 997338
Related literature
For background to terpyridine compounds, see: Constable (2008); Eryazici et al. (2008); Schubert et al. (2006); Wild et al. (2011); Zadykowicz & Potvin (1999); Wang & Hanan (2005). For similar dipyrazinylpyridine compounds, see: Dares et al. (2011); Dai et al. (2010a,b); Vougioukalakis et al. (2010); Liegghio et al. (2001).
Experimental
Crystal data
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Data collection: APEX2 (Bruker, 2004); cell SAINT (Bruker, 2004); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2009).
Supporting information
CCDC reference: 997338
10.1107/S1600536814008496/mw2121sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536814008496/mw2121Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536814008496/mw2121Isup3.cdx
Supporting information file. DOI: 10.1107/S1600536814008496/mw2121Isup4.cml
To 15 mL of a methanolic solution of 2-acetylpyrazine (0.813 g, 6.7 mmol) and 2-carboxybenzaldehyde (0.5 g, 3.3 mmol) was added 10 mL of an aqueous solution of potassium hydroxide (3.57 mol·L–1) and then 15 mL of concentrated ammonia. After stirring for 24 h, the solution was acidified to pH 3–4 using hydrochloric acid. The resulting yellow precipitate was collected and washed with water and ethanol (yield 97%). Yellow crystals were obtained by recrystallization from chloroform, m.p. 282.2–284.0°C. IR (υ/cm–1): 3134, 3047, 1717, 1604, 1470, 1374, 1250, 1119, 1015, 850, 760, 690, 626, 480; 1H NMR (400 MHz, CDCl3, TMS, δ/ppm): 9.83 (s, 2H, pyrazinyl NCHCN), 8.61 (m, 4H, pyrazinyl NCHCHN), 8.46 (s, 2H, pyridyl NCCH), 8.06 (d, 1H, phenyl CHCCOOH), 7.59 (t, 1H, phenyl CHCHCHCCOOH), 7.51 (t, 1H, phenyl CHCHCHCHCCOOH), 7.43 (d, 1H, phenyl CHCHCCOOH); ESI-MS: m/z = 354 ([M–H]–).
H atoms attached to C atoms were positioned geometrically and allowed to ride on their parent atoms, with C–H = 0.93 Å and Uiso(H) = 1.2Ueq(C). The carboxyl H atom was located in a difference Fourier map and treated with the riding-model approximation with Uiso(H) = 1.5Ueq(O).
Data collection: APEX2 (Bruker, 2004); cell
SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2009).C20H13N5O2 | Z = 2 |
Mr = 355.35 | F(000) = 368 |
Triclinic, P1 | Dx = 1.442 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 7.0253 (9) Å | Cell parameters from 753 reflections |
b = 10.9070 (14) Å | θ = 3.2–23.9° |
c = 11.3218 (14) Å | µ = 0.10 mm−1 |
α = 99.345 (2)° | T = 298 K |
β = 99.266 (2)° | Block, yellow |
γ = 102.513 (2)° | 0.22 × 0.16 × 0.15 mm |
V = 818.17 (18) Å3 |
Bruker APEXII CCD diffractometer | 2998 independent reflections |
Radiation source: fine-focus sealed tube | 1732 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.022 |
phi and ω scans | θmax = 25.5°, θmin = 1.9° |
Absorption correction: multi-scan (SADABS; Bruker, 2002) | h = −8→7 |
Tmin = 0.979, Tmax = 0.985 | k = −12→13 |
4395 measured reflections | l = −13→11 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.049 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.137 | H-atom parameters constrained |
S = 1.00 | w = 1/[σ2(Fo2) + (0.0595P)2 + 0.0149P] where P = (Fo2 + 2Fc2)/3 |
2998 reflections | (Δ/σ)max < 0.001 |
244 parameters | Δρmax = 0.16 e Å−3 |
0 restraints | Δρmin = −0.17 e Å−3 |
C20H13N5O2 | γ = 102.513 (2)° |
Mr = 355.35 | V = 818.17 (18) Å3 |
Triclinic, P1 | Z = 2 |
a = 7.0253 (9) Å | Mo Kα radiation |
b = 10.9070 (14) Å | µ = 0.10 mm−1 |
c = 11.3218 (14) Å | T = 298 K |
α = 99.345 (2)° | 0.22 × 0.16 × 0.15 mm |
β = 99.266 (2)° |
Bruker APEXII CCD diffractometer | 2998 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2002) | 1732 reflections with I > 2σ(I) |
Tmin = 0.979, Tmax = 0.985 | Rint = 0.022 |
4395 measured reflections |
R[F2 > 2σ(F2)] = 0.049 | 0 restraints |
wR(F2) = 0.137 | H-atom parameters constrained |
S = 1.00 | Δρmax = 0.16 e Å−3 |
2998 reflections | Δρmin = −0.17 e Å−3 |
244 parameters |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 | ||
C1 | 0.1728 (4) | −0.3687 (3) | 0.4584 (3) | 0.0532 (7) | |
H1 | 0.1637 | −0.4541 | 0.4627 | 0.064* | |
C2 | 0.1161 (4) | −0.3393 (3) | 0.3473 (3) | 0.0557 (8) | |
H2 | 0.0671 | −0.4056 | 0.2790 | 0.067* | |
C3 | 0.1994 (3) | −0.1281 (2) | 0.4341 (2) | 0.0380 (6) | |
C4 | 0.2524 (4) | −0.1594 (3) | 0.5464 (2) | 0.0495 (7) | |
H4 | 0.2986 | −0.0936 | 0.6153 | 0.059* | |
C5 | 0.2180 (3) | 0.0075 (2) | 0.4215 (2) | 0.0367 (6) | |
C6 | 0.1703 (4) | 0.0386 (2) | 0.3081 (2) | 0.0402 (6) | |
H6 | 0.1276 | −0.0256 | 0.2378 | 0.048* | |
C7 | 0.1866 (4) | 0.1655 (2) | 0.29993 (19) | 0.0366 (6) | |
C8 | 0.2548 (3) | 0.2569 (2) | 0.4075 (2) | 0.0385 (6) | |
H8 | 0.2702 | 0.3434 | 0.4059 | 0.046* | |
C9 | 0.3002 (3) | 0.2190 (2) | 0.5181 (2) | 0.0359 (6) | |
C10 | 0.3715 (3) | 0.3160 (2) | 0.63435 (19) | 0.0361 (6) | |
C11 | 0.4319 (4) | 0.2822 (3) | 0.7455 (2) | 0.0487 (7) | |
H11 | 0.4242 | 0.1963 | 0.7470 | 0.058* | |
C12 | 0.5066 (4) | 0.4901 (3) | 0.8416 (2) | 0.0560 (8) | |
H12 | 0.5546 | 0.5539 | 0.9120 | 0.067* | |
C13 | 0.4448 (4) | 0.5244 (3) | 0.7330 (2) | 0.0508 (7) | |
H13 | 0.4507 | 0.6102 | 0.7324 | 0.061* | |
C14 | 0.1170 (4) | 0.2064 (2) | 0.1841 (2) | 0.0387 (6) | |
C15 | −0.0200 (4) | 0.2817 (3) | 0.1901 (2) | 0.0500 (7) | |
H15 | −0.0553 | 0.3058 | 0.2646 | 0.060* | |
C16 | −0.1048 (4) | 0.3215 (3) | 0.0891 (2) | 0.0619 (8) | |
H16 | −0.1973 | 0.3704 | 0.0960 | 0.074* | |
C17 | −0.0530 (4) | 0.2893 (3) | −0.0211 (2) | 0.0583 (8) | |
H17 | −0.1086 | 0.3168 | −0.0891 | 0.070* | |
C18 | 0.0815 (4) | 0.2162 (2) | −0.0302 (2) | 0.0472 (7) | |
H18 | 0.1162 | 0.1944 | −0.1053 | 0.057* | |
C19 | 0.1680 (4) | 0.1736 (2) | 0.0699 (2) | 0.0384 (6) | |
C20 | 0.3147 (4) | 0.0977 (2) | 0.0456 (2) | 0.0441 (7) | |
N1 | 0.2823 (3) | 0.09612 (19) | 0.52578 (16) | 0.0382 (5) | |
N2 | 0.2399 (4) | −0.2799 (2) | 0.5597 (2) | 0.0571 (7) | |
N3 | 0.1286 (3) | −0.2189 (2) | 0.33310 (18) | 0.0492 (6) | |
N4 | 0.5000 (4) | 0.3688 (2) | 0.84957 (18) | 0.0592 (7) | |
N5 | 0.3768 (3) | 0.4380 (2) | 0.62871 (17) | 0.0457 (6) | |
O1 | 0.4479 (3) | 0.0935 (2) | 0.13504 (16) | 0.0668 (6) | |
H1A | 0.5194 | 0.0491 | 0.1102 | 0.100* | |
O2 | 0.3067 (3) | 0.0435 (2) | −0.06218 (15) | 0.0668 (6) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.067 (2) | 0.0413 (17) | 0.0645 (19) | 0.0228 (14) | 0.0308 (16) | 0.0198 (15) |
C2 | 0.071 (2) | 0.0374 (17) | 0.0585 (18) | 0.0121 (15) | 0.0171 (15) | 0.0081 (14) |
C3 | 0.0415 (15) | 0.0388 (15) | 0.0364 (14) | 0.0119 (12) | 0.0116 (11) | 0.0094 (11) |
C4 | 0.0631 (19) | 0.0448 (17) | 0.0455 (16) | 0.0180 (14) | 0.0160 (14) | 0.0120 (13) |
C5 | 0.0412 (14) | 0.0390 (15) | 0.0321 (13) | 0.0125 (11) | 0.0096 (11) | 0.0080 (11) |
C6 | 0.0514 (16) | 0.0365 (15) | 0.0327 (13) | 0.0140 (12) | 0.0070 (11) | 0.0052 (11) |
C7 | 0.0460 (15) | 0.0370 (15) | 0.0301 (13) | 0.0138 (12) | 0.0103 (11) | 0.0088 (11) |
C8 | 0.0513 (16) | 0.0356 (15) | 0.0345 (13) | 0.0166 (12) | 0.0136 (12) | 0.0115 (11) |
C9 | 0.0400 (14) | 0.0372 (15) | 0.0347 (13) | 0.0149 (11) | 0.0113 (11) | 0.0088 (11) |
C10 | 0.0382 (14) | 0.0396 (15) | 0.0318 (13) | 0.0104 (11) | 0.0099 (11) | 0.0066 (11) |
C11 | 0.0630 (18) | 0.0461 (17) | 0.0367 (14) | 0.0169 (14) | 0.0069 (13) | 0.0068 (12) |
C12 | 0.070 (2) | 0.0503 (19) | 0.0410 (16) | 0.0121 (15) | 0.0063 (14) | −0.0011 (13) |
C13 | 0.071 (2) | 0.0388 (16) | 0.0417 (15) | 0.0114 (14) | 0.0150 (14) | 0.0039 (12) |
C14 | 0.0488 (16) | 0.0344 (14) | 0.0326 (13) | 0.0099 (12) | 0.0071 (11) | 0.0072 (11) |
C15 | 0.0677 (19) | 0.0558 (18) | 0.0362 (15) | 0.0306 (15) | 0.0163 (13) | 0.0107 (13) |
C16 | 0.077 (2) | 0.075 (2) | 0.0508 (17) | 0.0470 (18) | 0.0171 (16) | 0.0203 (15) |
C17 | 0.078 (2) | 0.068 (2) | 0.0402 (16) | 0.0362 (17) | 0.0102 (15) | 0.0206 (14) |
C18 | 0.0608 (18) | 0.0507 (18) | 0.0310 (14) | 0.0151 (14) | 0.0101 (12) | 0.0079 (12) |
C19 | 0.0446 (15) | 0.0363 (15) | 0.0339 (13) | 0.0122 (12) | 0.0070 (11) | 0.0044 (11) |
C20 | 0.0526 (17) | 0.0422 (16) | 0.0350 (14) | 0.0090 (13) | 0.0080 (13) | 0.0051 (12) |
N1 | 0.0465 (13) | 0.0385 (13) | 0.0334 (11) | 0.0149 (10) | 0.0114 (9) | 0.0091 (9) |
N2 | 0.0798 (18) | 0.0509 (16) | 0.0544 (15) | 0.0276 (13) | 0.0260 (13) | 0.0226 (12) |
N3 | 0.0692 (16) | 0.0344 (13) | 0.0439 (13) | 0.0128 (11) | 0.0098 (11) | 0.0095 (10) |
N4 | 0.0834 (18) | 0.0574 (17) | 0.0339 (12) | 0.0208 (14) | 0.0025 (12) | 0.0060 (11) |
N5 | 0.0593 (15) | 0.0392 (13) | 0.0392 (12) | 0.0137 (11) | 0.0111 (11) | 0.0065 (10) |
O1 | 0.0674 (14) | 0.0972 (17) | 0.0447 (11) | 0.0458 (12) | 0.0097 (10) | 0.0071 (11) |
O2 | 0.0819 (15) | 0.0797 (15) | 0.0412 (11) | 0.0400 (12) | 0.0104 (10) | −0.0052 (10) |
C1—N2 | 1.320 (3) | C11—N4 | 1.331 (3) |
C1—C2 | 1.367 (3) | C11—H11 | 0.9300 |
C1—H1 | 0.9300 | C12—N4 | 1.332 (3) |
C2—N3 | 1.334 (3) | C12—C13 | 1.373 (3) |
C2—H2 | 0.9300 | C12—H12 | 0.9300 |
C3—N3 | 1.331 (3) | C13—N5 | 1.331 (3) |
C3—C4 | 1.384 (3) | C13—H13 | 0.9300 |
C3—C5 | 1.488 (3) | C14—C15 | 1.397 (3) |
C4—N2 | 1.334 (3) | C14—C19 | 1.408 (3) |
C4—H4 | 0.9300 | C15—C16 | 1.380 (3) |
C5—N1 | 1.342 (3) | C15—H15 | 0.9300 |
C5—C6 | 1.389 (3) | C16—C17 | 1.369 (3) |
C6—C7 | 1.382 (3) | C16—H16 | 0.9300 |
C6—H6 | 0.9300 | C17—C18 | 1.367 (4) |
C7—C8 | 1.385 (3) | C17—H17 | 0.9300 |
C7—C14 | 1.496 (3) | C18—C19 | 1.394 (3) |
C8—C9 | 1.391 (3) | C18—H18 | 0.9300 |
C8—H8 | 0.9300 | C19—C20 | 1.486 (3) |
C9—N1 | 1.337 (3) | C20—O2 | 1.254 (3) |
C9—C10 | 1.486 (3) | C20—O1 | 1.277 (3) |
C10—N5 | 1.336 (3) | O1—H1A | 0.8200 |
C10—C11 | 1.395 (3) | ||
N2—C1—C2 | 122.2 (3) | N4—C12—C13 | 122.3 (2) |
N2—C1—H1 | 118.9 | N4—C12—H12 | 118.8 |
C2—C1—H1 | 118.9 | C13—C12—H12 | 118.8 |
N3—C2—C1 | 122.5 (3) | N5—C13—C12 | 121.8 (3) |
N3—C2—H2 | 118.8 | N5—C13—H13 | 119.1 |
C1—C2—H2 | 118.8 | C12—C13—H13 | 119.1 |
N3—C3—C4 | 120.9 (2) | C15—C14—C19 | 117.0 (2) |
N3—C3—C5 | 117.6 (2) | C15—C14—C7 | 115.5 (2) |
C4—C3—C5 | 121.6 (2) | C19—C14—C7 | 127.4 (2) |
N2—C4—C3 | 122.7 (3) | C16—C15—C14 | 122.1 (2) |
N2—C4—H4 | 118.7 | C16—C15—H15 | 118.9 |
C3—C4—H4 | 118.7 | C14—C15—H15 | 118.9 |
N1—C5—C6 | 122.8 (2) | C17—C16—C15 | 120.1 (3) |
N1—C5—C3 | 115.9 (2) | C17—C16—H16 | 119.9 |
C6—C5—C3 | 121.3 (2) | C15—C16—H16 | 119.9 |
C7—C6—C5 | 119.8 (2) | C18—C17—C16 | 119.3 (3) |
C7—C6—H6 | 120.1 | C18—C17—H17 | 120.3 |
C5—C6—H6 | 120.1 | C16—C17—H17 | 120.3 |
C6—C7—C8 | 117.3 (2) | C17—C18—C19 | 121.8 (2) |
C6—C7—C14 | 123.3 (2) | C17—C18—H18 | 119.1 |
C8—C7—C14 | 119.1 (2) | C19—C18—H18 | 119.1 |
C7—C8—C9 | 119.9 (2) | C18—C19—C14 | 119.6 (2) |
C7—C8—H8 | 120.1 | C18—C19—C20 | 115.3 (2) |
C9—C8—H8 | 120.1 | C14—C19—C20 | 125.2 (2) |
N1—C9—C8 | 122.6 (2) | O2—C20—O1 | 122.5 (3) |
N1—C9—C10 | 117.0 (2) | O2—C20—C19 | 118.8 (2) |
C8—C9—C10 | 120.4 (2) | O1—C20—C19 | 118.7 (2) |
N5—C10—C11 | 120.8 (2) | C9—N1—C5 | 117.6 (2) |
N5—C10—C9 | 117.4 (2) | C1—N2—C4 | 115.6 (2) |
C11—C10—C9 | 121.8 (2) | C3—N3—C2 | 116.1 (2) |
N4—C11—C10 | 122.2 (3) | C11—N4—C12 | 116.1 (2) |
N4—C11—H11 | 118.9 | C13—N5—C10 | 116.8 (2) |
C10—C11—H11 | 118.9 | C20—O1—H1A | 109.5 |
N2—C1—C2—N3 | 1.4 (4) | C14—C15—C16—C17 | −1.1 (4) |
N3—C3—C4—N2 | 1.4 (4) | C15—C16—C17—C18 | 0.7 (5) |
C5—C3—C4—N2 | −179.0 (2) | C16—C17—C18—C19 | −0.1 (4) |
N3—C3—C5—N1 | 177.5 (2) | C17—C18—C19—C14 | −0.2 (4) |
C4—C3—C5—N1 | −2.2 (3) | C17—C18—C19—C20 | −178.6 (3) |
N3—C3—C5—C6 | −2.4 (3) | C15—C14—C19—C18 | −0.1 (4) |
C4—C3—C5—C6 | 178.0 (2) | C7—C14—C19—C18 | 177.1 (2) |
N1—C5—C6—C7 | −0.7 (4) | C15—C14—C19—C20 | 178.1 (2) |
C3—C5—C6—C7 | 179.1 (2) | C7—C14—C19—C20 | −4.6 (4) |
C5—C6—C7—C8 | 1.2 (3) | C18—C19—C20—O2 | −22.1 (3) |
C5—C6—C7—C14 | −172.8 (2) | C14—C19—C20—O2 | 159.6 (2) |
C6—C7—C8—C9 | −1.1 (3) | C18—C19—C20—O1 | 155.8 (2) |
C14—C7—C8—C9 | 173.2 (2) | C14—C19—C20—O1 | −22.5 (4) |
C7—C8—C9—N1 | 0.5 (4) | C8—C9—N1—C5 | 0.1 (3) |
C7—C8—C9—C10 | −179.4 (2) | C10—C9—N1—C5 | 179.9 (2) |
N1—C9—C10—N5 | −175.5 (2) | C6—C5—N1—C9 | 0.0 (3) |
C8—C9—C10—N5 | 4.4 (3) | C3—C5—N1—C9 | −179.8 (2) |
N1—C9—C10—C11 | 4.8 (3) | C2—C1—N2—C4 | −1.2 (4) |
C8—C9—C10—C11 | −175.3 (2) | C3—C4—N2—C1 | −0.2 (4) |
N5—C10—C11—N4 | −1.2 (4) | C4—C3—N3—C2 | −1.2 (4) |
C9—C10—C11—N4 | 178.5 (2) | C5—C3—N3—C2 | 179.2 (2) |
N4—C12—C13—N5 | −0.8 (4) | C1—C2—N3—C3 | −0.2 (4) |
C6—C7—C14—C15 | 123.9 (3) | C10—C11—N4—C12 | 0.3 (4) |
C8—C7—C14—C15 | −50.1 (3) | C13—C12—N4—C11 | 0.7 (4) |
C6—C7—C14—C19 | −53.4 (4) | C12—C13—N5—C10 | −0.1 (4) |
C8—C7—C14—C19 | 132.6 (3) | C11—C10—N5—C13 | 1.1 (3) |
C19—C14—C15—C16 | 0.8 (4) | C9—C10—N5—C13 | −178.6 (2) |
C7—C14—C15—C16 | −176.8 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1A···O2i | 0.82 | 1.84 | 2.656 (3) | 176 |
C15—H15···N2ii | 0.93 | 2.56 | 3.438 (3) | 157 |
Symmetry codes: (i) −x+1, −y, −z; (ii) −x, −y, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1A···O2i | 0.82 | 1.84 | 2.656 (3) | 176 |
C15—H15···N2ii | 0.93 | 2.56 | 3.438 (3) | 157 |
Symmetry codes: (i) −x+1, −y, −z; (ii) −x, −y, −z+1. |
Acknowledgements
Financial support from the South China Normal University is gratefully acknowledged.
References
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Terpyridine compounds are among the most frequently used tridentate ligands for transition metal elements (Constable, 2008; Eryazici et al., 2008; Schubert et al., 2006; Wild et al.). However, the similar dipyrazinylpyridine compounds have received much less attention and only a few structures have been reported (Dares et al., 2011; Dai et al., 2010a; Dai et al., 2010b; Vougioukalakis et al., 2010; Liegghio et al., 2001). We previously demonstrated that 4-p-tolyl-2,6-di(pyrazin-2-yl)pyridine has stronger intermolecular interactions than its isoelectronic counterpart 4-p-tolyl-2,2':6',2''-terpyridine (suggested by a 90°C higher melting point for the former) and their coordination behaviours are also somewhat different (Dai et al., 2010a). Herein we report the synthesis of 4-o-carboxyphenyl-2,6-di(pyrazin-2-yl)pyridine, (I), the first carboxyl-containing dipyrazinylpyridine compound, via by the Kröhnke reaction in a very convenient one-pot method in quantitative yield which contrasts with the frequently used two-step procedures for preparation of many terpyridine compounds (Schubert et al., 2006). The molecular structure of (I) is shown in Fig. 1. Both pyrazinyl rings have their ortho N-atoms anti to the central pyridyl N atom. This conformation is free of possible steric strain between the vicinal C–H groups of the central pyridyl and the peripheral pyrazinyl rings and also avoids the lone-pair repulsions between syn-- positioned N atoms (Zadykowicz & Potvin, 1999) as is commonly found for the non-coordinated terpyridine or dipyrazinylpyridine compounds (Dares et al., 2011; Dai et al., 2010b; Vougioukalakis et al., 2010; Liegghio et al., 2001). The two pyrazinyl rings are nearly coplanar with the pyridyl ring as the dihedral angles between the N3- and N5-containing pyrazinyl rings and the pyridyl ring are 2.21 (9)° and 4.57 (9)°, respectively. In contrast, the strong steric hindrance caused by the ortho-carboxyl group on the phenyl ring makes this ring rotate out of the attached pyridyl plane by 52.60 (9)°. The carboxyl group twists from the phenyl ring by 22.6 (1)°.
The O–H···O and C–H···N hydrogen bonds (Table 1) as well as the aromatic π–π stacking interactions direct the crystal packing. As displayed in Fig. 2, each planar dipyrazinylpyridine moiety is antiparallel to two other moieties above and below it generating π–π stacking interactions as evidenced by the centroid-centroid distances between the nearly parallel aromatic rings: Cg(N2/N3/C1–C4)···Cg(N1/C5–C9)i 3.9186 (4) Å and Cg(N2/N3/C1–C4)···Cg(N1/C5–C9)ii 3.9794 (5) Å [symmetry codes: (i) –x, –y, –z+1; (ii) x+1, y, z]. The presence of a C15–H15···N2i hydrogen bond (Table 1, Fig. 2) may account for the fact that the former centroid-centroid distance is a little shorter than the latter. The continuous stacking of the pyridyl and the N2-containing pyrazinyl rings leads to formation of infinite one-dimensional chains along the (100) direction. Between the neighbouring chains there are strong O1–H1A···O2iii [(iii) –x+1, –y, –z] hydrogen bonds (Table 1, Fig. 2) forming a two-dimensional supramolecular network parallel to (010). There are no significant interactions among these sheets.