organic compounds
H-imidazol-2-yl)-3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyrazin-6-amine
of 5-(4,5-dihydro-1aDepartment of Chemistry, Tulane University, New Orleans, LA 70118, USA, bChemistry and Environmental Division, Manchester Metropolitan University, Manchester M1 5GD, England, cChemistry Department, Faculty of Science, Minia University, 61519 El-Minia, Egypt, dDepartment of Physics, Faculty of Sciences, Erciyes University, 38039 Kayseri, Turkey, eDepartment of Chemistry, Faculty of Science, Assiut University, 71515 Assiut, Egypt, and fKirkuk University, College of Science, Department of Chemistry, Kirkuk, Iraq
*Correspondence e-mail: shaabankamel@yahoo.com
In the title compound, C15H15N7, the phenyl ring is inclined by 19.86 (5)° to the mean plane of the pyrazolo[3,4-b]pyrazine core. In the crystal, N—H⋯N and C—H⋯N hydrogen bonds form [010] chains, which stack via π–π interactions [centroid–centroid distance between the pyrazole rings = 3.4322 (7) Å].
Keywords: crystal structure; pyrazolo[3,4-b]pyrazine; hydrogen bonding; π–π interactions; scaffold compounds.
CCDC reference: 1031105
1. Related literature
For the synthesis of similar pyrazolo[3,4-b]pyrazines, see: El-Emary & El-Kashef (2013). For different biological and industrial applications of pyrazolopyrazine scaffold compounds, see: El-Emary et al. (1998); El-Kashef et al. (2000); El-Emary (2006); Rangnekar (1990).
2. Experimental
2.1. Crystal data
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2.3. Refinement
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Data collection: APEX2 (Bruker, 2014); cell SAINT (Bruker, 2014); data reduction: SAINT; program(s) used to solve structure: SHELXT (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2012); software used to prepare material for publication: SHELXTL2014 (Sheldrick, 2008).
Supporting information
CCDC reference: 1031105
10.1107/S160053681402354X/hg5415sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S160053681402354X/hg5415Isup2.hkl
Supporting information file. DOI: 10.1107/S160053681402354X/hg5415Isup3.cml
The title compound has been prepared according to our reported method (El-Kashef et al., 2000). The product was crystallized from dioxan to furnish a good yield (68%) of colourles crystals (m.p. 503–505 K) which were of suffiecient quality for X-ray diffraction.
H-atoms attached to carbon were placed in calculated positions (C—H = 0.95 - 0.98 Å) while those attached to nitrogen were placed in locations derived from a difference map and their parameters adjusted to give N—H = 0.91 Å. All were included as riding contributions with isotropic displacement parameters 1.2 - 1.5 times those of the attached atoms.
Data collection: APEX2 (Bruker, 2014); cell
SAINT (Bruker, 2014); data reduction: SAINT (Bruker, 2014); program(s) used to solve structure: SHELXT (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2012); software used to prepare material for publication: SHELXTL2014 (Sheldrick, 2008).Figure 1. The title molecule with numbering scheme and 50% probability ellipsoids. The intramolecular hydrogen bond is shown as a blue dotted line. Figure 2. Plan view of the chain showing N—H···N and C—H···N hydrogen bonds as blue and black dotted lines, respectively. Figure 3. Elevation view of two chains showing the π-π interactions as green dotted lines. Figure 4. Packing viewed down the a axis. |
C15H15N7 | F(000) = 1232 |
Mr = 293.34 | Dx = 1.415 Mg m−3 |
Monoclinic, C2/c | Cu Kα radiation, λ = 1.54178 Å |
a = 7.9412 (2) Å | Cell parameters from 9946 reflections |
b = 15.7078 (3) Å | θ = 4.0–71.7° |
c = 22.3276 (4) Å | µ = 0.75 mm−1 |
β = 98.573 (1)° | T = 150 K |
V = 2754.00 (10) Å3 | Block, colourless |
Z = 8 | 0.15 × 0.10 × 0.05 mm |
Bruker D8 VENTURE PHOTON 100 CMOS diffractometer | 2685 independent reflections |
Radiation source: INCOATEC IµS micro–focus source | 2335 reflections with I > 2σ(I) |
Mirror monochromator | Rint = 0.031 |
Detector resolution: 10.4167 pixels mm-1 | θmax = 72.0°, θmin = 4.0° |
ω scans | h = −9→9 |
Absorption correction: multi-scan (SADABS; Bruker, 2014) | k = −19→18 |
Tmin = 0.93, Tmax = 0.97 | l = −25→27 |
21033 measured reflections |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: mixed |
R[F2 > 2σ(F2)] = 0.035 | H-atom parameters constrained |
wR(F2) = 0.094 | w = 1/[σ2(Fo2) + (0.047P)2 + 1.7272P] where P = (Fo2 + 2Fc2)/3 |
S = 1.04 | (Δ/σ)max < 0.001 |
2685 reflections | Δρmax = 0.23 e Å−3 |
201 parameters | Δρmin = −0.17 e Å−3 |
0 restraints | Extinction correction: SHELXL2014 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.00012 (3) |
C15H15N7 | V = 2754.00 (10) Å3 |
Mr = 293.34 | Z = 8 |
Monoclinic, C2/c | Cu Kα radiation |
a = 7.9412 (2) Å | µ = 0.75 mm−1 |
b = 15.7078 (3) Å | T = 150 K |
c = 22.3276 (4) Å | 0.15 × 0.10 × 0.05 mm |
β = 98.573 (1)° |
Bruker D8 VENTURE PHOTON 100 CMOS diffractometer | 2685 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2014) | 2335 reflections with I > 2σ(I) |
Tmin = 0.93, Tmax = 0.97 | Rint = 0.031 |
21033 measured reflections |
R[F2 > 2σ(F2)] = 0.035 | 0 restraints |
wR(F2) = 0.094 | H-atom parameters constrained |
S = 1.04 | Δρmax = 0.23 e Å−3 |
2685 reflections | Δρmin = −0.17 e Å−3 |
201 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. H-atoms attached to carbon were placed in calculated positions (C—H = 0.95 - 0.98 Å) while those attached to nitrogen were placed in locations derived from a difference map and their parameters adjusted to give N—H = 0.91 Å. All were included as riding contributions with isotropic displacement parameters 1.2 - 1.5 times those of the attached atoms. |
x | y | z | Uiso*/Ueq | ||
N1 | 0.21440 (13) | 0.23938 (6) | 0.22995 (4) | 0.0252 (2) | |
N2 | 0.24278 (14) | 0.15429 (6) | 0.24683 (5) | 0.0284 (3) | |
N3 | 0.49830 (13) | 0.27132 (6) | 0.36366 (5) | 0.0255 (2) | |
N4 | 0.31514 (13) | 0.37679 (6) | 0.27055 (4) | 0.0258 (2) | |
N5 | 0.43603 (15) | 0.49390 (7) | 0.32160 (5) | 0.0350 (3) | |
H5A | 0.5051 | 0.5149 | 0.3545 | 0.042* | |
H5B | 0.3806 | 0.5295 | 0.2931 | 0.042* | |
N6 | 0.62895 (15) | 0.47203 (7) | 0.43134 (5) | 0.0345 (3) | |
N7 | 0.69317 (15) | 0.33776 (7) | 0.46313 (5) | 0.0339 (3) | |
H7A | 0.7265 | 0.2859 | 0.4511 | 0.041* | |
C1 | 0.10360 (15) | 0.25899 (8) | 0.17597 (5) | 0.0255 (3) | |
C2 | 0.03232 (16) | 0.33968 (8) | 0.16704 (6) | 0.0292 (3) | |
H2 | 0.0600 | 0.3829 | 0.1967 | 0.035* | |
C3 | −0.07919 (17) | 0.35656 (9) | 0.11468 (6) | 0.0325 (3) | |
H3 | −0.1269 | 0.4119 | 0.1083 | 0.039* | |
C4 | −0.12216 (18) | 0.29404 (9) | 0.07151 (6) | 0.0366 (3) | |
H4 | −0.2016 | 0.3057 | 0.0363 | 0.044* | |
C5 | −0.04798 (19) | 0.21408 (9) | 0.08019 (6) | 0.0382 (3) | |
H5 | −0.0757 | 0.1711 | 0.0504 | 0.046* | |
C6 | 0.06600 (18) | 0.19648 (8) | 0.13184 (6) | 0.0322 (3) | |
H6 | 0.1183 | 0.1421 | 0.1371 | 0.039* | |
C7 | 0.30685 (15) | 0.29182 (8) | 0.27108 (5) | 0.0241 (3) | |
C8 | 0.39641 (15) | 0.23910 (8) | 0.31557 (5) | 0.0251 (3) | |
C9 | 0.35066 (16) | 0.15415 (8) | 0.29763 (6) | 0.0278 (3) | |
C10 | 0.4086 (2) | 0.07325 (9) | 0.32887 (7) | 0.0377 (3) | |
H10A | 0.3465 | 0.0253 | 0.3079 | 0.057* | |
H10B | 0.3866 | 0.0753 | 0.3709 | 0.057* | |
H10C | 0.5309 | 0.0659 | 0.3284 | 0.057* | |
C11 | 0.41803 (16) | 0.40912 (8) | 0.31815 (5) | 0.0260 (3) | |
C12 | 0.50810 (15) | 0.35545 (8) | 0.36559 (5) | 0.0253 (3) | |
C13 | 0.61270 (16) | 0.39176 (8) | 0.41964 (5) | 0.0263 (3) | |
C14 | 0.80754 (19) | 0.38977 (9) | 0.50567 (6) | 0.0366 (3) | |
H14A | 0.9268 | 0.3854 | 0.4980 | 0.044* | |
H14B | 0.8018 | 0.3736 | 0.5482 | 0.044* | |
C15 | 0.73523 (19) | 0.47864 (9) | 0.49128 (6) | 0.0380 (3) | |
H15A | 0.6658 | 0.4970 | 0.5223 | 0.046* | |
H15B | 0.8283 | 0.5203 | 0.4901 | 0.046* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0278 (5) | 0.0214 (5) | 0.0242 (5) | −0.0011 (4) | −0.0036 (4) | −0.0001 (4) |
N2 | 0.0326 (6) | 0.0213 (5) | 0.0288 (6) | −0.0016 (4) | −0.0037 (4) | 0.0005 (4) |
N3 | 0.0263 (5) | 0.0237 (5) | 0.0250 (5) | −0.0011 (4) | −0.0008 (4) | −0.0008 (4) |
N4 | 0.0269 (6) | 0.0230 (5) | 0.0256 (5) | −0.0006 (4) | −0.0019 (4) | −0.0005 (4) |
N5 | 0.0429 (7) | 0.0222 (5) | 0.0345 (6) | 0.0006 (5) | −0.0123 (5) | −0.0005 (4) |
N6 | 0.0385 (6) | 0.0279 (6) | 0.0329 (6) | −0.0012 (5) | −0.0082 (5) | −0.0059 (5) |
N7 | 0.0434 (7) | 0.0270 (6) | 0.0269 (6) | −0.0027 (5) | −0.0087 (5) | −0.0004 (4) |
C1 | 0.0244 (6) | 0.0276 (6) | 0.0233 (6) | −0.0040 (5) | −0.0007 (5) | 0.0017 (5) |
C2 | 0.0300 (7) | 0.0289 (7) | 0.0269 (6) | 0.0004 (5) | −0.0014 (5) | −0.0016 (5) |
C3 | 0.0319 (7) | 0.0319 (7) | 0.0315 (7) | 0.0023 (5) | −0.0024 (6) | 0.0031 (5) |
C4 | 0.0370 (7) | 0.0396 (8) | 0.0289 (7) | −0.0038 (6) | −0.0095 (6) | 0.0032 (6) |
C5 | 0.0465 (8) | 0.0337 (7) | 0.0301 (7) | −0.0065 (6) | −0.0088 (6) | −0.0033 (6) |
C6 | 0.0387 (7) | 0.0251 (6) | 0.0300 (7) | −0.0030 (5) | −0.0035 (6) | −0.0002 (5) |
C7 | 0.0232 (6) | 0.0249 (6) | 0.0233 (6) | −0.0013 (5) | 0.0009 (5) | −0.0011 (5) |
C8 | 0.0260 (6) | 0.0233 (6) | 0.0245 (6) | 0.0000 (5) | −0.0010 (5) | 0.0002 (5) |
C9 | 0.0300 (7) | 0.0246 (6) | 0.0270 (6) | −0.0013 (5) | −0.0018 (5) | −0.0002 (5) |
C10 | 0.0463 (8) | 0.0254 (7) | 0.0364 (7) | −0.0021 (6) | −0.0108 (6) | 0.0029 (5) |
C11 | 0.0261 (6) | 0.0244 (6) | 0.0262 (6) | 0.0006 (5) | −0.0004 (5) | −0.0016 (5) |
C12 | 0.0251 (6) | 0.0243 (6) | 0.0253 (6) | −0.0011 (5) | 0.0005 (5) | −0.0016 (5) |
C13 | 0.0259 (6) | 0.0268 (6) | 0.0252 (6) | −0.0011 (5) | 0.0007 (5) | −0.0008 (5) |
C14 | 0.0408 (8) | 0.0371 (7) | 0.0280 (7) | −0.0054 (6) | −0.0075 (6) | −0.0028 (6) |
C15 | 0.0398 (8) | 0.0359 (7) | 0.0339 (7) | −0.0033 (6) | −0.0089 (6) | −0.0089 (6) |
N1—C7 | 1.3638 (15) | C3—C4 | 1.3826 (19) |
N1—N2 | 1.3978 (14) | C3—H3 | 0.9500 |
N1—C1 | 1.4161 (16) | C4—C5 | 1.389 (2) |
N2—C9 | 1.3158 (17) | C4—H4 | 0.9500 |
N3—C12 | 1.3241 (16) | C5—C6 | 1.3836 (19) |
N3—C8 | 1.3435 (16) | C5—H5 | 0.9500 |
N4—C7 | 1.3365 (16) | C6—H6 | 0.9500 |
N4—C11 | 1.3401 (16) | C7—C8 | 1.4028 (17) |
N5—C11 | 1.3404 (16) | C8—C9 | 1.4246 (17) |
N5—H5A | 0.9100 | C9—C10 | 1.4891 (18) |
N5—H5B | 0.9099 | C10—H10A | 0.9800 |
N6—C13 | 1.2902 (17) | C10—H10B | 0.9800 |
N6—C15 | 1.4755 (17) | C10—H10C | 0.9800 |
N7—C13 | 1.3732 (16) | C11—C12 | 1.4554 (17) |
N7—C14 | 1.4620 (17) | C12—C13 | 1.4741 (16) |
N7—H7A | 0.9099 | C14—C15 | 1.525 (2) |
C1—C2 | 1.3904 (18) | C14—H14A | 0.9900 |
C1—C6 | 1.3916 (18) | C14—H14B | 0.9900 |
C2—C3 | 1.3829 (18) | C15—H15A | 0.9900 |
C2—H2 | 0.9500 | C15—H15B | 0.9900 |
C7—N1—N2 | 110.30 (10) | N3—C8—C7 | 121.67 (11) |
C7—N1—C1 | 130.20 (10) | N3—C8—C9 | 132.50 (11) |
N2—N1—C1 | 119.48 (10) | C7—C8—C9 | 105.83 (11) |
C9—N2—N1 | 106.98 (10) | N2—C9—C8 | 110.29 (11) |
C12—N3—C8 | 115.30 (10) | N2—C9—C10 | 121.41 (11) |
C7—N4—C11 | 113.36 (10) | C8—C9—C10 | 128.29 (11) |
C11—N5—H5A | 116.9 | C9—C10—H10A | 109.5 |
C11—N5—H5B | 122.3 | C9—C10—H10B | 109.5 |
H5A—N5—H5B | 120.8 | H10A—C10—H10B | 109.5 |
C13—N6—C15 | 106.19 (11) | C9—C10—H10C | 109.5 |
C13—N7—C14 | 107.03 (11) | H10A—C10—H10C | 109.5 |
C13—N7—H7A | 118.0 | H10B—C10—H10C | 109.5 |
C14—N7—H7A | 120.9 | N4—C11—N5 | 117.98 (11) |
C2—C1—C6 | 120.12 (12) | N4—C11—C12 | 122.21 (11) |
C2—C1—N1 | 120.56 (11) | N5—C11—C12 | 119.81 (11) |
C6—C1—N1 | 119.31 (11) | N3—C12—C11 | 122.30 (11) |
C3—C2—C1 | 119.46 (12) | N3—C12—C13 | 115.85 (11) |
C3—C2—H2 | 120.3 | C11—C12—C13 | 121.83 (11) |
C1—C2—H2 | 120.3 | N6—C13—N7 | 116.00 (11) |
C4—C3—C2 | 120.89 (13) | N6—C13—C12 | 124.83 (11) |
C4—C3—H3 | 119.6 | N7—C13—C12 | 119.08 (11) |
C2—C3—H3 | 119.6 | N7—C14—C15 | 101.34 (10) |
C3—C4—C5 | 119.33 (12) | N7—C14—H14A | 111.5 |
C3—C4—H4 | 120.3 | C15—C14—H14A | 111.5 |
C5—C4—H4 | 120.3 | N7—C14—H14B | 111.5 |
C6—C5—C4 | 120.54 (13) | C15—C14—H14B | 111.5 |
C6—C5—H5 | 119.7 | H14A—C14—H14B | 109.3 |
C4—C5—H5 | 119.7 | N6—C15—C14 | 105.85 (10) |
C5—C6—C1 | 119.60 (13) | N6—C15—H15A | 110.6 |
C5—C6—H6 | 120.2 | C14—C15—H15A | 110.6 |
C1—C6—H6 | 120.2 | N6—C15—H15B | 110.6 |
N4—C7—N1 | 128.29 (11) | C14—C15—H15B | 110.6 |
N4—C7—C8 | 125.12 (11) | H15A—C15—H15B | 108.7 |
N1—C7—C8 | 106.59 (10) | ||
C7—N1—N2—C9 | 0.15 (14) | N1—N2—C9—C8 | −0.06 (15) |
C1—N1—N2—C9 | 179.34 (11) | N1—N2—C9—C10 | 179.61 (12) |
C7—N1—C1—C2 | −20.6 (2) | N3—C8—C9—N2 | 178.77 (13) |
N2—N1—C1—C2 | 160.36 (11) | C7—C8—C9—N2 | −0.05 (15) |
C7—N1—C1—C6 | 159.58 (12) | N3—C8—C9—C10 | −0.9 (2) |
N2—N1—C1—C6 | −19.42 (17) | C7—C8—C9—C10 | −179.69 (14) |
C6—C1—C2—C3 | 1.55 (19) | C7—N4—C11—N5 | 179.53 (11) |
N1—C1—C2—C3 | −178.23 (11) | C7—N4—C11—C12 | −0.94 (17) |
C1—C2—C3—C4 | 0.8 (2) | C8—N3—C12—C11 | −1.44 (17) |
C2—C3—C4—C5 | −2.0 (2) | C8—N3—C12—C13 | 177.08 (10) |
C3—C4—C5—C6 | 0.9 (2) | N4—C11—C12—N3 | 2.23 (19) |
C4—C5—C6—C1 | 1.4 (2) | N5—C11—C12—N3 | −178.24 (12) |
C2—C1—C6—C5 | −2.6 (2) | N4—C11—C12—C13 | −176.20 (11) |
N1—C1—C6—C5 | 177.17 (12) | N5—C11—C12—C13 | 3.32 (18) |
C11—N4—C7—N1 | 179.70 (12) | C15—N6—C13—N7 | 0.00 (16) |
C11—N4—C7—C8 | −0.87 (18) | C15—N6—C13—C12 | 176.46 (12) |
N2—N1—C7—N4 | 179.34 (12) | C14—N7—C13—N6 | −12.26 (16) |
C1—N1—C7—N4 | 0.3 (2) | C14—N7—C13—C12 | 171.07 (11) |
N2—N1—C7—C8 | −0.18 (13) | N3—C12—C13—N6 | −175.55 (12) |
C1—N1—C7—C8 | −179.25 (12) | C11—C12—C13—N6 | 3.0 (2) |
C12—N3—C8—C7 | −0.33 (17) | N3—C12—C13—N7 | 0.80 (17) |
C12—N3—C8—C9 | −178.99 (13) | C11—C12—C13—N7 | 179.33 (11) |
N4—C7—C8—N3 | 1.63 (19) | C13—N7—C14—C15 | 17.78 (15) |
N1—C7—C8—N3 | −178.84 (11) | C13—N6—C15—C14 | 11.67 (16) |
N4—C7—C8—C9 | −179.40 (12) | N7—C14—C15—N6 | −17.76 (15) |
N1—C7—C8—C9 | 0.14 (13) |
D—H···A | D—H | H···A | D···A | D—H···A |
C6—H6···N5i | 0.95 | 2.56 | 3.3483 (17) | 140 |
N5—H5B···N2ii | 0.91 | 2.31 | 3.1702 (15) | 158 |
N5—H5A···N6 | 0.91 | 1.97 | 2.7111 (15) | 138 |
Symmetry codes: (i) −x+1/2, y−1/2, −z+1/2; (ii) −x+1/2, y+1/2, −z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
C6—H6···N5i | 0.95 | 2.56 | 3.3483 (17) | 140 |
N5—H5B···N2ii | 0.91 | 2.31 | 3.1702 (15) | 158 |
N5—H5A···N6 | 0.91 | 1.97 | 2.7111 (15) | 138 |
Symmetry codes: (i) −x+1/2, y−1/2, −z+1/2; (ii) −x+1/2, y+1/2, −z+1/2. |
Acknowledgements
The support of NSF–MRI grant No. 1228232 for the purchase of the diffractometer and Tulane University for support of the Tulane Crystallography Laboratory are gratefully acknowledged. In addition, TIE would like to express his thanks to Professor H. M. S. El-Kashef, Assiut University, for his contribution to this study.
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Pyrazine scaffold compounds are an interesting class of fused heterocyclic compounds due to their diverse properties in medicinal and applied chemistry. Pyrazolo[3,4-b]pyrazine derivatives have been reported to act as blood platelet aggregation inhibitors and bone metabolism improvers (El-Emary & El-Kashef, 2013). They also show antifungal and antiparasitic activities (El-Emary et al., 1998; El-Kashef et al., 2000; El-Emary, 2006). In addition, they are used as dye dispersants and as fluorescents (Rangnekar, 1990). In view of this medicinal importance, the crystal structure determination of the title compound was carried out and the results are presented here.
In the title compound, the pyrazolo[3,4-b]pyrazine core is planar (r.m.s. deviation 0.0089) with the phenyl ring inclined by 19.86 (5)° to it. An intramolecular N5—H5a···N6 hydrogen bond (Table 1 and Fig. 1) keeps the dihydroimidazolyl substituent nearly coplanar with the core. Intermolecular N5—H5b···N2 and C6—H6···N5 hydrogen bonds form chains of molecules (Table 1 and Fig. 2) which stack via π–π interactions between pyrazine rings (Cgi···Cgii = Cgiii··· Cgiv = 3.43 Å. Cgi: 0.5 - x, 1/2 + y, 0.5 - z; Cgii: -1/2 + x, 1/2 + y, z; Cgiii: 0.5 - x, -1/2 + y, 0.5 - z; Cgiv: -1/2 + x, -1/2 + y, z. Figs. 3 and 4). The chains run approximately parallel to (102).