organic compounds
4-(1H-Indol-3-yl)-2,6-bis(pyrazin-2-yl)pyridine
aInstitute of Molecular Science, Shanxi University, Taiyuan, Shanxi 030006, People's Republic of China
*Correspondence e-mail: cxyuan@sxu.edu.cn
In the title compound, C21H14N6, the pyridine ring and two pyrazine rings are nearly coplanar [dihedral angles = 2.03 (7) and 1.60 (7)°], while the dihedral angle between the indole ring system and the pyridine ring is 29.04 (6)°. In the crystal, molecules are linked by N—H⋯N hydrogen bonds, which generate [10] chains. The packing is consolidated by C—H⋯N hydrogen bonds and aromatic π–π stacking, generating a three-dimensional network.
Keywords: crystal structure; pyridine; hydrogen-bonding; π–π interaction.
CCDC reference: 1832711
Structure description
Pyridine/pyrazine ligands have attracted attention for the synthesis of transition-metal complexes with a variety of geometries (Sengupta et al. 2017; Rajput & Mukherjee 2013). Specifically, many terpyridine compounds, as convergent tridentate chelating N-donor ligands, have been synthesized and their coordination chemistries have been explored (Yin et al. 2015; Constable 2007; Wild et al. 2011). However, there is less research about the dipyrazinylpyridine compounds, which are close analogues of the terpyridines (Dai et al. 2010; Li et al. 2017).
The molecular structure of the title compound is illustrated in Fig. 1. The pyridine ring and the N1 and N4 pyrazine rings are nearly coplanar [dihedral angles = 2.03 (7) and 1.60 (7)°, respectively], indicating significant electronic conjugation, but the indole ring system deviates significantly from the pyridine ring [dihedral angle = 29.04 (6)°].
The N1 and N4 atoms of the pyrazine rings adopt trans conformations to the N3 atom of the central pyridine moiety, which does not seem to be a good conformation for a tridentate ligand. However, the single bond between the pyrazine ring and pyridine ring is easy to rotate freely in solution, so some tridentate metal complexes can also be obtained under appropriate conditions, for example the reported cadmium complexes with dipyrazinylpyridine ligands (Xie et al. 2016; Dai et al. 2010).
In the crystal, the N4 and N5 atoms in one pyrazine moiety accept C3—H3⋯N4 and N6—H6A⋯N5 hydrogen bonds, as shown in Fig. 2 and Table 1. The N—H⋯N hydrogen bonds generate [10] chains, which are cross-linked by the C—H⋯N bonds. Moreover, π–π stacking interactions between the pyrazine and pyridine rings are also observed (Fig. 3). The ring-centroid distances between the pyrazine ring and the adjacent pyridine and indole rings are 3.7925 (11) and 3.8044 (11) Å, respectively. The overall packing is shown in Fig. 4.
Synthesis and crystallization
0.1 mmol of Pt(DMSO)2Cl2 (DMSO = dimethyl sulfoxide) was added to a stirring solution of 2,6-bis(2-pyrazinyl)-4-(indol-1-yl)pyridine (0.1 mmol) in 15 ml of methanol. The solution was refluxed at 338 K for 5 h under a nitrogen atmosphere, cooled slowly and filtered. The filtrate was kept at room temperature and after about two weeks colorless block-shaped crystals of the title compound were collected by filtration.
Refinement
Crystal data, data collection and structure . One outlier with was removed from the final DISP instructions appropriate to the synchrotron wavelength were used in the refinement.
details are summarized in Table 2Structural data
CCDC reference: 1832711
https://doi.org/10.1107/S2414314618004923/hb4213sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314618004923/hb4213Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2414314618004923/hb4213Isup3.cml
Data collection: mar555; cell
HKL-2000 (Minor et al., 2000); data reduction: HKL-2000 (Minor et al., 2000); program(s) used to solve structure: SHELXL97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).C21H14N6 | F(000) = 728 |
Mr = 350.38 | Dx = 1.383 Mg m−3 |
Monoclinic, P21/c | Synchrotron radiation, λ = 0.710 Å |
a = 8.5560 (17) Å | Cell parameters from 8169 reflections |
b = 8.9820 (18) Å | θ = 2.4–29.5° |
c = 22.130 (4) Å | µ = 0.09 mm−1 |
β = 98.28 (3)° | T = 100 K |
V = 1683.0 (6) Å3 | Block, colorless |
Z = 4 | 0.20 × 0.20 × 0.15 mm |
Mar555 diffractometer | 2746 reflections with I > 2σ(I) |
Radiation source: synchrotron, 3W1A at BSRF | Rint = 0.136 |
oscillation mode scans | θmax = 25.1°, θmin = 2.5° |
Absorption correction: multi-scan (SCALEPACK; Otwinowski & Minor, 1997) | h = 0→10 |
Tmin = 0.983, Tmax = 0.987 | k = −10→10 |
5341 measured reflections | l = −26→26 |
2943 independent reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.053 | H-atom parameters constrained |
wR(F2) = 0.161 | w = 1/[σ2(Fo2) + (0.0852P)2 + 0.3936P] where P = (Fo2 + 2Fc2)/3 |
S = 1.04 | (Δ/σ)max = 0.001 |
2943 reflections | Δρmax = 0.39 e Å−3 |
244 parameters | Δρmin = −0.23 e Å−3 |
0 restraints |
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. |
x | y | z | Uiso*/Ueq | ||
C1 | 1.03422 (15) | 0.27853 (16) | 0.37871 (6) | 0.0206 (3) | |
C2 | 1.15461 (16) | 0.20143 (18) | 0.35555 (6) | 0.0238 (4) | |
H2 | 1.2202 | 0.1367 | 0.3820 | 0.029* | |
C3 | 1.08481 (17) | 0.3086 (2) | 0.26267 (7) | 0.0300 (4) | |
H3 | 1.0992 | 0.3226 | 0.2213 | 0.036* | |
C4 | 0.96495 (18) | 0.38505 (19) | 0.28541 (7) | 0.0291 (4) | |
H4 | 0.8996 | 0.4499 | 0.2589 | 0.035* | |
C5 | 1.29758 (16) | −0.05260 (17) | 0.66620 (7) | 0.0246 (4) | |
H5 | 1.2917 | −0.0663 | 0.7084 | 0.029* | |
C6 | 1.41440 (16) | −0.12564 (17) | 0.64057 (7) | 0.0243 (4) | |
H6 | 1.4869 | −0.1872 | 0.6658 | 0.029* | |
C7 | 1.20761 (15) | 0.05372 (16) | 0.57419 (6) | 0.0187 (3) | |
C8 | 1.32527 (15) | −0.02103 (17) | 0.54830 (6) | 0.0225 (4) | |
H8 | 1.3323 | −0.0068 | 0.5062 | 0.027* | |
C9 | 1.09203 (15) | 0.15450 (16) | 0.53679 (6) | 0.0184 (3) | |
C10 | 1.00918 (15) | 0.26218 (16) | 0.44353 (6) | 0.0192 (3) | |
C11 | 0.89131 (15) | 0.34194 (16) | 0.46693 (6) | 0.0195 (3) | |
H11 | 0.8246 | 0.4075 | 0.4413 | 0.023* | |
C12 | 0.97715 (15) | 0.22973 (16) | 0.56388 (6) | 0.0202 (3) | |
H12 | 0.9706 | 0.2164 | 0.6060 | 0.024* | |
C13 | 0.87170 (15) | 0.32504 (16) | 0.52825 (6) | 0.0193 (3) | |
C14 | 0.74714 (15) | 0.40481 (16) | 0.55418 (6) | 0.0195 (3) | |
C15 | 0.68268 (14) | 0.53939 (16) | 0.53282 (6) | 0.0194 (3) | |
H15 | 0.7116 | 0.5926 | 0.4990 | 0.023* | |
C16 | 0.66742 (14) | 0.36347 (17) | 0.60505 (6) | 0.0191 (3) | |
C17 | 0.67148 (16) | 0.23950 (17) | 0.64456 (6) | 0.0234 (4) | |
H17 | 0.7442 | 0.1608 | 0.6416 | 0.028* | |
C18 | 0.56950 (17) | 0.23335 (18) | 0.68735 (7) | 0.0264 (4) | |
H18 | 0.5737 | 0.1505 | 0.7142 | 0.032* | |
C19 | 0.45876 (16) | 0.34818 (19) | 0.69195 (6) | 0.0265 (4) | |
H19 | 0.3885 | 0.3407 | 0.7214 | 0.032* | |
C20 | 0.45158 (16) | 0.47124 (18) | 0.65405 (6) | 0.0244 (4) | |
H20 | 0.3771 | 0.5484 | 0.6569 | 0.029* | |
C21 | 0.55699 (15) | 0.47885 (16) | 0.61143 (6) | 0.0203 (3) | |
N1 | 0.93776 (14) | 0.37132 (15) | 0.34299 (6) | 0.0252 (3) | |
N2 | 1.18128 (14) | 0.21474 (17) | 0.29804 (6) | 0.0288 (4) | |
N3 | 1.10821 (12) | 0.16745 (14) | 0.47763 (5) | 0.0191 (3) | |
N4 | 1.19234 (13) | 0.03709 (14) | 0.63322 (5) | 0.0218 (3) | |
N5 | 1.42847 (14) | −0.11231 (15) | 0.58137 (6) | 0.0251 (3) | |
N6 | 0.57157 (13) | 0.58462 (14) | 0.56739 (5) | 0.0211 (3) | |
H6A | 0.5176 | 0.6682 | 0.5624 | 0.025* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0160 (6) | 0.0159 (7) | 0.0264 (7) | −0.0035 (6) | −0.0083 (5) | 0.0009 (6) |
C2 | 0.0202 (7) | 0.0233 (8) | 0.0256 (7) | 0.0010 (6) | −0.0049 (5) | −0.0004 (6) |
C3 | 0.0279 (7) | 0.0348 (10) | 0.0245 (7) | −0.0040 (7) | −0.0059 (6) | 0.0019 (7) |
C4 | 0.0278 (7) | 0.0289 (9) | 0.0275 (7) | 0.0004 (7) | −0.0068 (6) | 0.0066 (7) |
C5 | 0.0237 (7) | 0.0203 (8) | 0.0264 (7) | 0.0027 (6) | −0.0077 (5) | 0.0028 (6) |
C6 | 0.0213 (7) | 0.0170 (8) | 0.0309 (7) | 0.0048 (6) | −0.0092 (5) | 0.0007 (6) |
C7 | 0.0166 (6) | 0.0125 (7) | 0.0243 (7) | −0.0010 (6) | −0.0056 (5) | −0.0011 (6) |
C8 | 0.0196 (7) | 0.0189 (8) | 0.0265 (7) | 0.0039 (6) | −0.0055 (5) | 0.0006 (6) |
C9 | 0.0160 (6) | 0.0119 (7) | 0.0246 (7) | −0.0011 (6) | −0.0058 (5) | −0.0003 (6) |
C10 | 0.0152 (6) | 0.0135 (7) | 0.0259 (7) | −0.0015 (5) | −0.0077 (5) | −0.0003 (6) |
C11 | 0.0151 (6) | 0.0141 (7) | 0.0262 (7) | 0.0005 (6) | −0.0071 (5) | 0.0015 (6) |
C12 | 0.0183 (6) | 0.0160 (7) | 0.0238 (7) | −0.0003 (6) | −0.0058 (5) | 0.0007 (6) |
C13 | 0.0145 (6) | 0.0130 (7) | 0.0276 (7) | −0.0011 (6) | −0.0068 (5) | −0.0014 (6) |
C14 | 0.0157 (6) | 0.0160 (8) | 0.0236 (7) | 0.0011 (6) | −0.0086 (5) | −0.0024 (6) |
C15 | 0.0152 (6) | 0.0160 (7) | 0.0238 (7) | −0.0006 (5) | −0.0084 (5) | −0.0011 (6) |
C16 | 0.0147 (6) | 0.0163 (7) | 0.0233 (7) | 0.0008 (5) | −0.0077 (5) | −0.0037 (6) |
C17 | 0.0214 (7) | 0.0174 (8) | 0.0287 (7) | 0.0025 (6) | −0.0055 (5) | 0.0010 (6) |
C18 | 0.0264 (7) | 0.0223 (8) | 0.0280 (7) | −0.0031 (6) | −0.0048 (6) | 0.0041 (6) |
C19 | 0.0195 (7) | 0.0320 (9) | 0.0263 (7) | −0.0019 (6) | −0.0025 (5) | −0.0027 (7) |
C20 | 0.0176 (7) | 0.0252 (8) | 0.0273 (7) | 0.0031 (6) | −0.0073 (5) | −0.0044 (7) |
C21 | 0.0158 (6) | 0.0173 (7) | 0.0239 (7) | 0.0014 (6) | −0.0099 (5) | −0.0028 (6) |
N1 | 0.0234 (6) | 0.0234 (7) | 0.0262 (6) | 0.0021 (5) | −0.0054 (4) | 0.0045 (6) |
N2 | 0.0246 (6) | 0.0338 (8) | 0.0262 (6) | 0.0005 (6) | −0.0025 (5) | −0.0012 (6) |
N3 | 0.0157 (5) | 0.0137 (6) | 0.0253 (6) | −0.0007 (5) | −0.0057 (4) | 0.0007 (5) |
N4 | 0.0192 (6) | 0.0176 (7) | 0.0258 (6) | 0.0023 (5) | −0.0066 (4) | 0.0017 (5) |
N5 | 0.0207 (6) | 0.0203 (7) | 0.0312 (7) | 0.0073 (5) | −0.0064 (5) | −0.0005 (6) |
N6 | 0.0173 (6) | 0.0154 (6) | 0.0273 (6) | 0.0038 (5) | −0.0080 (4) | −0.0008 (5) |
C1—N1 | 1.3463 (18) | C10—C11 | 1.396 (2) |
C1—C2 | 1.398 (2) | C11—C13 | 1.399 (2) |
C1—C10 | 1.488 (2) | C11—H11 | 0.9500 |
C2—N2 | 1.330 (2) | C12—C13 | 1.4014 (19) |
C2—H2 | 0.9500 | C12—H12 | 0.9500 |
C3—N2 | 1.348 (2) | C13—C14 | 1.468 (2) |
C3—C4 | 1.388 (2) | C14—C15 | 1.383 (2) |
C3—H3 | 0.9500 | C14—C16 | 1.446 (2) |
C4—N1 | 1.334 (2) | C15—N6 | 1.3650 (19) |
C4—H4 | 0.9500 | C15—H15 | 0.9500 |
C5—N4 | 1.3429 (18) | C16—C17 | 1.413 (2) |
C5—C6 | 1.384 (2) | C16—C21 | 1.423 (2) |
C5—H5 | 0.9500 | C17—C18 | 1.378 (2) |
C6—N5 | 1.338 (2) | C17—H17 | 0.9500 |
C6—H6 | 0.9500 | C18—C19 | 1.414 (2) |
C7—N4 | 1.3399 (19) | C18—H18 | 0.9500 |
C7—C8 | 1.399 (2) | C19—C20 | 1.384 (2) |
C7—C9 | 1.4989 (18) | C19—H19 | 0.9500 |
C8—N5 | 1.3422 (18) | C20—C21 | 1.397 (2) |
C8—H8 | 0.9500 | C20—H20 | 0.9500 |
C9—N3 | 1.3412 (19) | C21—N6 | 1.380 (2) |
C9—C12 | 1.397 (2) | N6—H6A | 0.8800 |
C10—N3 | 1.3518 (18) | ||
N1—C1—C2 | 120.87 (13) | C11—C13—C12 | 117.03 (13) |
N1—C1—C10 | 117.77 (13) | C11—C13—C14 | 121.42 (12) |
C2—C1—C10 | 121.36 (12) | C12—C13—C14 | 121.55 (13) |
N2—C2—C1 | 122.89 (13) | C15—C14—C16 | 106.31 (12) |
N2—C2—H2 | 118.6 | C15—C14—C13 | 124.70 (13) |
C1—C2—H2 | 118.6 | C16—C14—C13 | 129.00 (13) |
N2—C3—C4 | 121.44 (14) | N6—C15—C14 | 110.13 (13) |
N2—C3—H3 | 119.3 | N6—C15—H15 | 124.9 |
C4—C3—H3 | 119.3 | C14—C15—H15 | 124.9 |
N1—C4—C3 | 122.71 (14) | C17—C16—C21 | 118.03 (13) |
N1—C4—H4 | 118.6 | C17—C16—C14 | 135.37 (14) |
C3—C4—H4 | 118.6 | C21—C16—C14 | 106.53 (12) |
N4—C5—C6 | 121.94 (13) | C18—C17—C16 | 119.68 (15) |
N4—C5—H5 | 119.0 | C18—C17—H17 | 120.2 |
C6—C5—H5 | 119.0 | C16—C17—H17 | 120.2 |
N5—C6—C5 | 122.08 (13) | C17—C18—C19 | 121.15 (15) |
N5—C6—H6 | 119.0 | C17—C18—H18 | 119.4 |
C5—C6—H6 | 119.0 | C19—C18—H18 | 119.4 |
N4—C7—C8 | 121.51 (12) | C20—C19—C18 | 120.72 (14) |
N4—C7—C9 | 117.16 (12) | C20—C19—H19 | 119.6 |
C8—C7—C9 | 121.33 (13) | C18—C19—H19 | 119.6 |
N5—C8—C7 | 121.69 (13) | C19—C20—C21 | 118.14 (14) |
N5—C8—H8 | 119.2 | C19—C20—H20 | 120.9 |
C7—C8—H8 | 119.2 | C21—C20—H20 | 120.9 |
N3—C9—C12 | 123.70 (12) | N6—C21—C20 | 130.04 (14) |
N3—C9—C7 | 116.02 (12) | N6—C21—C16 | 107.61 (12) |
C12—C9—C7 | 120.28 (12) | C20—C21—C16 | 122.26 (14) |
N3—C10—C11 | 122.97 (13) | C4—N1—C1 | 116.21 (13) |
N3—C10—C1 | 115.76 (12) | C2—N2—C3 | 115.88 (13) |
C11—C10—C1 | 121.26 (12) | C9—N3—C10 | 117.06 (12) |
C10—C11—C13 | 119.86 (12) | C7—N4—C5 | 116.42 (12) |
C10—C11—H11 | 120.1 | C6—N5—C8 | 116.34 (13) |
C13—C11—H11 | 120.1 | C15—N6—C21 | 109.40 (12) |
C9—C12—C13 | 119.33 (13) | C15—N6—H6A | 125.3 |
C9—C12—H12 | 120.3 | C21—N6—H6A | 125.3 |
C13—C12—H12 | 120.3 | ||
N1—C1—C2—N2 | 0.2 (2) | C15—C14—C16—C21 | −0.06 (14) |
C10—C1—C2—N2 | −179.25 (13) | C13—C14—C16—C21 | −179.99 (12) |
N2—C3—C4—N1 | 0.1 (2) | C21—C16—C17—C18 | 0.3 (2) |
N4—C5—C6—N5 | −0.6 (2) | C14—C16—C17—C18 | −176.23 (15) |
N4—C7—C8—N5 | −0.2 (2) | C16—C17—C18—C19 | 0.9 (2) |
C9—C7—C8—N5 | −179.50 (12) | C17—C18—C19—C20 | −1.0 (2) |
N4—C7—C9—N3 | −178.98 (12) | C18—C19—C20—C21 | −0.2 (2) |
C8—C7—C9—N3 | 0.3 (2) | C19—C20—C21—N6 | 177.50 (13) |
N4—C7—C9—C12 | 1.70 (19) | C19—C20—C21—C16 | 1.5 (2) |
C8—C7—C9—C12 | −179.00 (13) | C17—C16—C21—N6 | −178.34 (11) |
N1—C1—C10—N3 | 179.73 (12) | C14—C16—C21—N6 | −0.88 (14) |
C2—C1—C10—N3 | −0.8 (2) | C17—C16—C21—C20 | −1.56 (19) |
N1—C1—C10—C11 | −1.0 (2) | C14—C16—C21—C20 | 175.90 (12) |
C2—C1—C10—C11 | 178.47 (13) | C3—C4—N1—C1 | 0.3 (2) |
N3—C10—C11—C13 | −0.2 (2) | C2—C1—N1—C4 | −0.4 (2) |
C1—C10—C11—C13 | −179.44 (12) | C10—C1—N1—C4 | 179.03 (13) |
N3—C9—C12—C13 | −0.2 (2) | C1—C2—N2—C3 | 0.2 (2) |
C7—C9—C12—C13 | 179.10 (12) | C4—C3—N2—C2 | −0.4 (2) |
C10—C11—C13—C12 | 1.8 (2) | C12—C9—N3—C10 | 1.8 (2) |
C10—C11—C13—C14 | −178.80 (12) | C7—C9—N3—C10 | −177.52 (11) |
C9—C12—C13—C11 | −1.6 (2) | C11—C10—N3—C9 | −1.6 (2) |
C9—C12—C13—C14 | 178.97 (12) | C1—C10—N3—C9 | 177.70 (11) |
C11—C13—C14—C15 | −27.0 (2) | C8—C7—N4—C5 | 1.2 (2) |
C12—C13—C14—C15 | 152.40 (13) | C9—C7—N4—C5 | −179.48 (12) |
C11—C13—C14—C16 | 152.92 (14) | C6—C5—N4—C7 | −0.8 (2) |
C12—C13—C14—C16 | −27.7 (2) | C5—C6—N5—C8 | 1.6 (2) |
C16—C14—C15—N6 | 1.00 (14) | C7—C8—N5—C6 | −1.2 (2) |
C13—C14—C15—N6 | −179.07 (12) | C14—C15—N6—C21 | −1.60 (15) |
C15—C14—C16—C17 | 176.75 (14) | C20—C21—N6—C15 | −174.92 (13) |
C13—C14—C16—C17 | −3.2 (3) | C16—C21—N6—C15 | 1.52 (15) |
D—H···A | D—H | H···A | D···A | D—H···A |
N6—H6A···N5i | 0.88 | 2.18 | 3.0190 (19) | 160 |
C3—H3···N4ii | 0.95 | 2.54 | 3.425 (2) | 155 |
Symmetry codes: (i) x−1, y+1, z; (ii) x, −y+1/2, z−1/2. |
Acknowledgements
The authors thank Zeng-Qiang Gao for assistance with the data collection of the title compound.
Funding information
Funding for this research was provided by: National Natural Science Foundation of China (grant No. 21471092).
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