2,5-Bis[4-(dimethyl-amino)-phen-yl]-3,6-dimethyl-pyrazine.

The title compound, C(22)H(26)N(4), was prepared from p-dimethyl-amino-propiophenone in six steps. The mol-ecule has no crystallographic symmetry. The dihedral angles between the pyrazine ring and the phenyl rings are 35.81 (6) and 37.11 (8)°. The dimethyl-amino groups are essentially planar (sum of the bond angles at N = 359.3 and 359.9°) and nearly coplanar with the adjacent aromatic ring [dihedral angles = 5.54 (11) and 7.40 (3)°]. This effect and the short aniline C-N bonds can be rationalised in terms of charge transfer from the amino groups to the central pyrazine ring.

Related literature

The title compound was prepared as a fundamental chromophore and as an inter­mediate for the preparation of acidochromic dyes, see: Detert & Sugiono (2005 ▶); Schmitt et al. (2008 ▶); Nemkovich et al. (2010 ▶). Conjugated oligomers with a pyrazine center and lateral donors are solvatochromic probes, see: Collette & Harper (2003 ▶) and Schmitt et al. (2011 ▶). 2,5-Diphenyl­pyrazine shows inter­planar angles of about 21° (Pieterse et al., 2000 ▶); due to steric hindrance these angles are opened up to 37–49° in the tetra­phenyl­pyrazine (Bartnik et al., 1999 ▶). The planarization of terminal amino groups and short aniline C—N bonds due to strong electronic coupling has also been observed in 2,5-bis­(p-dimethyl­amino­styr­yl)pyrazine, see: Fischer et al. (2011 ▶).

Experimental

Crystal data

C22H26N4

M = 346.47

Triclinic,

a = 9.459 (1) Å

b = 9.6368 (16) Å

c = 11.9661 (15) Å

α = 73.30 (1)°

β = 69.465 (11)°

γ = 74.446 (10)°

V = 961.2 (2) Å3

Z = 2

Cu Kα radiation

μ = 0.56 mm−1

T = 193 K

0.40 × 0.20 × 0.05 mm

Data collection

Enraf–Nonius CAD-4 diffractometer

3876 measured reflections

3646 independent reflections

2922 reflections with I > 2σ(I)

R int = 0.027

3 standard reflections every 60 min intensity decay: 2%

Refinement

R[F 2 > 2σ(F 2)] = 0.063

wR(F 2) = 0.218

S = 1.07

3646 reflections

242 parameters

H-atom parameters constrained

Δρmax = 0.43 e Å−3

Δρmin = −0.42 e Å−3

Data collection: CAD-4 Software (Enraf–Nonius, 1989 ▶); cell refinement: CAD-4 Software; data reduction: CORINC (Dräger & Gattow, 1971 ▶); program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2009 ▶); software used to prepare material for publication: PLATON.

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053681101748X/bt5544sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S160053681101748X/bt5544Isup2.hkl

Supplementary material file. DOI: 10.1107/S160053681101748X/bt5544Isup3.cdx

Supplementary material file. DOI: 10.1107/S160053681101748X/bt5544Isup4.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

C22H26N4	Z = 2
Mr = 346.47	F(000) = 372
Triclinic, P1	Dx = 1.197 Mg m−3
Hall symbol: -P 1	Melting point: 484 K
a = 9.459 (1) Å	Cu Kα radiation, λ = 1.54178 Å
b = 9.6368 (16) Å	Cell parameters from 25 reflections
c = 11.9661 (15) Å	θ = 60–69°
α = 73.30 (1)°	µ = 0.56 mm−1
β = 69.465 (11)°	T = 193 K
γ = 74.446 (10)°	Plate, yellow
V = 961.2 (2) Å3	0.40 × 0.20 × 0.05 mm

Enraf–Nonius CAD-4 diffractometer	Rint = 0.027
Radiation source: rotating anode	θmax = 70.0°, θmin = 4.0°
graphite	h = −11→11
ω/2θ scans	k = −11→0
3876 measured reflections	l = −14→13
3646 independent reflections	3 standard reflections every 60 min
2922 reflections with I > 2σ(I)	intensity decay: 2%

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)] = 0.063	H-atom parameters constrained
wR(F2) = 0.218	w = 1/[σ2(Fo2) + (0.1432P)2 + 0.2122P] where P = (Fo2 + 2Fc2)/3
S = 1.07	(Δ/σ)max < 0.001
3646 reflections	Δρmax = 0.43 e Å−3
242 parameters	Δρmin = −0.42 e Å−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.012 (2)

Experimental. 1H-NMR (CDCl3): δ = 7.55 (d, J = 8.7 Hz, 4 H, 2-H, 6-H phenyl); 6.79 (br. d, J = 8.8 Hz, 4 H, 3-H, 5-H, phenyl); 3.03 (s, 12 H, N-CH3); 2.64 (s, 6 H, pyrazin-CH3). 13C-NMR (CDCl3): δ = 150.3, 150.1, 147.5 (C-2, C-3 pyrazine, C-1 phenyl), 130.5, 127.9 (C-2, C-3, C-5, C-6 phenyl), 112.9, 41.2 (N(CH3)2), 23.3 (CH3). FD-MS : 346.5 (100%) [M+] IR (ATR): ν = 2918.7, 1607.4, 1528.3, 1438.6, 1389.5, 1359.6, 1231.2, 1194.7, 1161.9, 943.0, 818.6, 785.9, 674.0 cm-1.

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
C1	0.4300 (2)	0.7610 (2)	0.62142 (18)	0.0308 (4)
N2	0.55091 (18)	0.65153 (18)	0.59277 (15)	0.0339 (4)
C3	0.6186 (2)	0.6432 (2)	0.47567 (18)	0.0335 (5)
C4	0.5629 (2)	0.7449 (2)	0.38283 (18)	0.0321 (5)
N5	0.44665 (18)	0.85760 (18)	0.41135 (15)	0.0333 (4)
C6	0.3811 (2)	0.8678 (2)	0.52829 (18)	0.0328 (5)
C7	0.7572 (2)	0.5220 (2)	0.45446 (19)	0.0434 (6)
H7A	0.8089	0.5052	0.5165	0.065*
H7B	0.8282	0.5505	0.3731	0.065*
H7C	0.7249	0.4312	0.4599	0.065*
C8	0.2599 (2)	1.0036 (2)	0.54900 (19)	0.0407 (5)
H8A	0.1592	0.9828	0.5607	0.061*
H8B	0.2831	1.0845	0.4779	0.061*
H8C	0.2586	1.0316	0.6219	0.061*
C9	0.3625 (2)	0.7599 (2)	0.75399 (18)	0.0313 (5)
C10	0.4576 (2)	0.7140 (2)	0.82934 (18)	0.0343 (5)
H10	0.5649	0.6846	0.7941	0.041*
C11	0.4019 (2)	0.7099 (2)	0.95281 (18)	0.0345 (5)
H11	0.4708	0.6781	1.0008	0.041*
C12	0.2435 (2)	0.7525 (2)	1.00883 (17)	0.0307 (5)
C13	0.1460 (2)	0.7930 (2)	0.93438 (18)	0.0331 (5)
H13	0.0380	0.8179	0.9697	0.040*
C14	0.2057 (2)	0.7971 (2)	0.81013 (18)	0.0327 (5)
H14	0.1374	0.8263	0.7618	0.039*
N15	0.18654 (19)	0.7556 (2)	1.13101 (15)	0.0389 (5)
C16	0.0227 (2)	0.7857 (3)	1.18829 (19)	0.0425 (5)
H16A	−0.0203	0.8861	1.1522	0.064*
H16B	0.0019	0.7762	1.2761	0.064*
H16C	−0.0249	0.7152	1.1755	0.064*
C17	0.2880 (3)	0.7075 (3)	1.20702 (19)	0.0435 (5)
H17A	0.3251	0.6008	1.2163	0.065*
H17B	0.2320	0.7306	1.2875	0.065*
H17C	0.3756	0.7584	1.1687	0.065*
C18	0.6290 (2)	0.7442 (2)	0.25089 (18)	0.0313 (5)
C19	0.6822 (2)	0.6145 (2)	0.20663 (18)	0.0341 (5)
H19	0.6779	0.5222	0.2629	0.041*
C20	0.7408 (2)	0.6174 (2)	0.08291 (18)	0.0339 (5)
H20	0.7764	0.5270	0.0561	0.041*
C21	0.7490 (2)	0.7497 (2)	−0.00351 (17)	0.0310 (5)
C22	0.6928 (2)	0.8808 (2)	0.04087 (18)	0.0331 (5)
H22	0.6945	0.9734	−0.0152	0.040*
C23	0.6352 (2)	0.8763 (2)	0.16485 (17)	0.0317 (5)
H23	0.5987	0.9664	0.1921	0.038*
N24	0.8089 (2)	0.75325 (19)	−0.12682 (15)	0.0399 (5)
C25	0.8785 (3)	0.6186 (2)	−0.1704 (2)	0.0449 (6)
H25A	0.9618	0.5652	−0.1348	0.067*
H25B	0.9200	0.6421	−0.2597	0.067*
H25C	0.8010	0.5570	−0.1465	0.067*
C26	0.7970 (3)	0.8908 (2)	−0.21529 (19)	0.0436 (5)
H26A	0.6886	0.9379	−0.2025	0.065*
H26B	0.8410	0.8716	−0.2979	0.065*
H26C	0.8532	0.9562	−0.2054	0.065*

	U11	U22	U33	U12	U13	U23
C1	0.0270 (9)	0.0304 (10)	0.0347 (10)	−0.0053 (7)	−0.0072 (8)	−0.0089 (8)
N2	0.0298 (8)	0.0339 (9)	0.0336 (9)	−0.0026 (7)	−0.0059 (7)	−0.0080 (7)
C3	0.0294 (9)	0.0339 (10)	0.0331 (10)	−0.0039 (8)	−0.0054 (8)	−0.0074 (8)
C4	0.0279 (9)	0.0323 (10)	0.0359 (10)	−0.0058 (8)	−0.0081 (8)	−0.0086 (8)
N5	0.0293 (8)	0.0345 (9)	0.0344 (9)	−0.0024 (7)	−0.0086 (7)	−0.0090 (7)
C6	0.0286 (9)	0.0340 (10)	0.0354 (10)	−0.0036 (8)	−0.0092 (8)	−0.0093 (8)
C7	0.0392 (11)	0.0414 (12)	0.0367 (11)	0.0079 (9)	−0.0084 (9)	−0.0071 (9)
C8	0.0383 (11)	0.0385 (11)	0.0386 (11)	0.0019 (9)	−0.0085 (9)	−0.0101 (9)
C9	0.0299 (9)	0.0313 (10)	0.0331 (10)	−0.0047 (8)	−0.0082 (8)	−0.0099 (8)
C10	0.0243 (9)	0.0371 (11)	0.0411 (11)	−0.0020 (8)	−0.0092 (8)	−0.0122 (8)
C11	0.0285 (9)	0.0395 (11)	0.0393 (11)	−0.0049 (8)	−0.0146 (8)	−0.0097 (8)
C12	0.0306 (10)	0.0304 (10)	0.0331 (10)	−0.0073 (8)	−0.0095 (8)	−0.0083 (8)
C13	0.0238 (9)	0.0378 (11)	0.0371 (10)	−0.0036 (7)	−0.0083 (7)	−0.0104 (8)
C14	0.0271 (9)	0.0380 (11)	0.0366 (10)	−0.0060 (8)	−0.0125 (8)	−0.0095 (8)
N15	0.0325 (9)	0.0514 (11)	0.0335 (9)	−0.0063 (8)	−0.0100 (7)	−0.0111 (8)
C16	0.0375 (11)	0.0494 (13)	0.0371 (11)	−0.0048 (9)	−0.0052 (9)	−0.0143 (9)
C17	0.0486 (12)	0.0466 (13)	0.0378 (11)	−0.0036 (10)	−0.0191 (9)	−0.0097 (9)
C18	0.0254 (9)	0.0346 (10)	0.0352 (10)	−0.0055 (8)	−0.0089 (8)	−0.0096 (8)
C19	0.0323 (10)	0.0326 (10)	0.0382 (11)	−0.0050 (8)	−0.0116 (8)	−0.0081 (8)
C20	0.0318 (10)	0.0316 (10)	0.0405 (11)	−0.0039 (8)	−0.0110 (8)	−0.0123 (8)
C21	0.0249 (9)	0.0342 (11)	0.0365 (10)	−0.0033 (8)	−0.0111 (8)	−0.0113 (8)
C22	0.0323 (10)	0.0313 (10)	0.0357 (10)	−0.0056 (8)	−0.0104 (8)	−0.0071 (8)
C23	0.0281 (9)	0.0290 (10)	0.0392 (10)	−0.0038 (7)	−0.0093 (8)	−0.0115 (8)
N24	0.0459 (10)	0.0381 (10)	0.0343 (10)	−0.0021 (8)	−0.0112 (8)	−0.0120 (8)
C25	0.0479 (12)	0.0444 (12)	0.0426 (12)	0.0013 (10)	−0.0130 (10)	−0.0194 (10)
C26	0.0465 (12)	0.0432 (12)	0.0375 (11)	−0.0042 (10)	−0.0119 (9)	−0.0079 (9)

C1—N2	1.350 (2)	N15—C16	1.444 (3)
C1—C6	1.401 (3)	N15—C17	1.447 (3)
C1—C9	1.486 (3)	C16—H16A	0.9800
N2—C3	1.337 (2)	C16—H16B	0.9800
C3—C4	1.407 (3)	C16—H16C	0.9800
C3—C7	1.504 (3)	C17—H17A	0.9800
C4—N5	1.347 (2)	C17—H17B	0.9800
C4—C18	1.481 (3)	C17—H17C	0.9800
N5—C6	1.338 (2)	C18—C23	1.388 (3)
C6—C8	1.507 (3)	C18—C19	1.398 (3)
C7—H7A	0.9800	C19—C20	1.382 (3)
C7—H7B	0.9800	C19—H19	0.9500
C7—H7C	0.9800	C20—C21	1.393 (3)
C8—H8A	0.9800	C20—H20	0.9500
C8—H8B	0.9800	C21—N24	1.376 (2)
C8—H8C	0.9800	C21—C22	1.410 (3)
C9—C14	1.391 (3)	C22—C23	1.381 (3)
C9—C10	1.395 (3)	C22—H22	0.9500
C10—C11	1.376 (3)	C23—H23	0.9500
C10—H10	0.9500	N24—C25	1.442 (3)
C11—C12	1.410 (3)	N24—C26	1.445 (3)
C11—H11	0.9500	C25—H25A	0.9800
C12—N15	1.376 (2)	C25—H25B	0.9800
C12—C13	1.407 (3)	C25—H25C	0.9800
C13—C14	1.386 (3)	C26—H26A	0.9800
C13—H13	0.9500	C26—H26B	0.9800
C14—H14	0.9500	C26—H26C	0.9800
N2—C1—C6	119.83 (17)	C16—N15—C17	118.93 (17)
N2—C1—C9	115.15 (17)	N15—C16—H16A	109.5
C6—C1—C9	124.97 (17)	N15—C16—H16B	109.5
C3—N2—C1	119.37 (17)	H16A—C16—H16B	109.5
N2—C3—C4	120.69 (18)	N15—C16—H16C	109.5
N2—C3—C7	114.53 (17)	H16A—C16—H16C	109.5
C4—C3—C7	124.75 (17)	H16B—C16—H16C	109.5
N5—C4—C3	119.63 (18)	N15—C17—H17A	109.5
N5—C4—C18	115.47 (17)	N15—C17—H17B	109.5
C3—C4—C18	124.79 (17)	H17A—C17—H17B	109.5
C6—N5—C4	119.54 (17)	N15—C17—H17C	109.5
N5—C6—C1	120.72 (18)	H17A—C17—H17C	109.5
N5—C6—C8	115.08 (17)	H17B—C17—H17C	109.5
C1—C6—C8	124.14 (18)	C23—C18—C19	117.00 (18)
C3—C7—H7A	109.5	C23—C18—C4	120.18 (17)
C3—C7—H7B	109.5	C19—C18—C4	122.78 (18)
H7A—C7—H7B	109.5	C20—C19—C18	121.52 (18)
C3—C7—H7C	109.5	C20—C19—H19	119.2
H7A—C7—H7C	109.5	C18—C19—H19	119.2
H7B—C7—H7C	109.5	C19—C20—C21	121.55 (18)
C6—C8—H8A	109.5	C19—C20—H20	119.2
C6—C8—H8B	109.5	C21—C20—H20	119.2
H8A—C8—H8B	109.5	N24—C21—C20	121.82 (18)
C6—C8—H8C	109.5	N24—C21—C22	121.17 (18)
H8A—C8—H8C	109.5	C20—C21—C22	117.01 (18)
H8B—C8—H8C	109.5	C23—C22—C21	120.81 (18)
C14—C9—C10	116.81 (18)	C23—C22—H22	119.6
C14—C9—C1	123.42 (17)	C21—C22—H22	119.6
C10—C9—C1	119.72 (17)	C22—C23—C18	122.09 (18)
C11—C10—C9	122.45 (17)	C22—C23—H23	119.0
C11—C10—H10	118.8	C18—C23—H23	119.0
C9—C10—H10	118.8	C21—N24—C25	120.54 (17)
C10—C11—C12	120.62 (17)	C21—N24—C26	120.83 (17)
C10—C11—H11	119.7	C25—N24—C26	118.57 (17)
C12—C11—H11	119.7	N24—C25—H25A	109.5
N15—C12—C13	121.30 (17)	N24—C25—H25B	109.5
N15—C12—C11	121.43 (17)	H25A—C25—H25B	109.5
C13—C12—C11	117.27 (17)	N24—C25—H25C	109.5
C14—C13—C12	120.70 (17)	H25A—C25—H25C	109.5
C14—C13—H13	119.6	H25B—C25—H25C	109.5
C12—C13—H13	119.6	N24—C26—H26A	109.5
C13—C14—C9	122.06 (17)	N24—C26—H26B	109.5
C13—C14—H14	119.0	H26A—C26—H26B	109.5
C9—C14—H14	119.0	N24—C26—H26C	109.5
C12—N15—C16	120.04 (16)	H26A—C26—H26C	109.5
C12—N15—C17	120.38 (17)	H26B—C26—H26C	109.5
C6—C1—N2—C3	−2.7 (3)	C11—C12—C13—C14	−2.9 (3)
C9—C1—N2—C3	179.60 (17)	C12—C13—C14—C9	0.9 (3)
C1—N2—C3—C4	−1.5 (3)	C10—C9—C14—C13	1.7 (3)
C1—N2—C3—C7	176.75 (18)	C1—C9—C14—C13	179.07 (18)
N2—C3—C4—N5	4.4 (3)	C13—C12—N15—C16	6.7 (3)
C7—C3—C4—N5	−173.64 (19)	C11—C12—N15—C16	−173.95 (19)
N2—C3—C4—C18	−179.55 (18)	C13—C12—N15—C17	177.36 (18)
C7—C3—C4—C18	2.4 (3)	C11—C12—N15—C17	−3.3 (3)
C3—C4—N5—C6	−2.9 (3)	N5—C4—C18—C23	33.3 (3)
C18—C4—N5—C6	−179.32 (17)	C3—C4—C18—C23	−142.9 (2)
C4—N5—C6—C1	−1.3 (3)	N5—C4—C18—C19	−144.41 (19)
C4—N5—C6—C8	175.93 (17)	C3—C4—C18—C19	39.4 (3)
N2—C1—C6—N5	4.2 (3)	C23—C18—C19—C20	1.1 (3)
C9—C1—C6—N5	−178.35 (18)	C4—C18—C19—C20	178.86 (17)
N2—C1—C6—C8	−172.74 (18)	C18—C19—C20—C21	−0.3 (3)
C9—C1—C6—C8	4.7 (3)	C19—C20—C21—N24	179.26 (17)
N2—C1—C9—C14	−142.6 (2)	C19—C20—C21—C22	−0.8 (3)
C6—C1—C9—C14	39.9 (3)	N24—C21—C22—C23	−178.92 (17)
N2—C1—C9—C10	34.8 (3)	C20—C21—C22—C23	1.2 (3)
C6—C1—C9—C10	−142.8 (2)	C21—C22—C23—C18	−0.4 (3)
C14—C9—C10—C11	−2.2 (3)	C19—C18—C23—C22	−0.8 (3)
C1—C9—C10—C11	−179.68 (18)	C4—C18—C23—C22	−178.57 (17)
C9—C10—C11—C12	0.1 (3)	C20—C21—N24—C25	−5.7 (3)
C10—C11—C12—N15	−176.91 (18)	C22—C21—N24—C25	174.39 (18)
C10—C11—C12—C13	2.5 (3)	C20—C21—N24—C26	171.36 (18)
N15—C12—C13—C14	176.43 (18)	C22—C21—N24—C26	−8.5 (3)