organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

Monoclinic polymorph of 2,5-bis­[4-(di­methyl­amino)­styr­yl]-3,6-di­methyl­pyrazine

aUniversity Mainz, Duesbergweg 10-14, 55099 Mainz, Germany
*Correspondence e-mail: detert@uni-mainz.de

(Received 20 January 2011; accepted 18 February 2011; online 12 March 2011)

The title compound, C26H30N4, was prepared by condensation of tetra­methyl­pyrazine and dimethyl­amino­benzaldehyde and crystallizes from chloro­form/methanol in two different forms. Block-shaped crystals belong to the monoclinic crystal system and plates to the triclinic system. The two crystal forms differ in the arrangement of the centrosymmetric mol­ecules, which have nearly identical geometries. In the monoclinic crystals reported here, planar mol­ecules [maximum deviation = 0.062 (2) Å], with a transoid arrangement of the (E)-styryl units and completely planarized dimethylamino groups [sum of the C—N bond angles = 359.9 (2)°], form layers connected via H–π-stacking. The dihedral angle between the central and pendant rings is 1.30 (8)°. The triclinic polymorph contains two half molecules, both completed by crystallographic inversion symmetry.

Related literature

The title compound was synthesized as a fundamental chromophore in a larger project focusing on solvatochromic and acidochromic dyes for sensing applications via one and two-photon excited fluorescence, see: Nemkovich et al. (2010[Nemkovich, N. A., Detert, H. & Schmitt, V. (2010). Chem. Phys. 378, 37-41.]); Schmitt et al. (2008[Schmitt, V., Glang, S., Preis, J. & Detert, H. (2008). Adv. Sci. Technol. 55, 36-41.]); Detert & Schmitt (2006[Detert, H. & Schmitt, V. (2006). J. Phys. Org. Chem. 19, 603-607.]); Strehmel et al. (2003[Strehmel, B., Sarker, A. M. & Detert, H. (2003). ChemPhysChem, 4, 249-259.]). Starting with 2,5-dimethyl­pyrazine, linear distyryl­pyrazines had been prepared by acid-catalyzed condensations with benzaldehyde (Takahashi & Satake, 1952[Takahashi, T. & Satake, K. (1952). Yakugaku Zasshi, 8, 1188-1192 CAN 47:44597.]) as well as via Siegrist reaction with the anils of alk­oxy­benzaldehydes (Zerban, 1991[Zerban, G. (1991). PhD thesis, University of Mainz, Germany.]). Crystal data for the triclinic form have been deposited (CCDC 807782).

[Scheme 1]

Experimental

Crystal data
  • C26H30N4

  • Mr = 398.54

  • Monoclinic, P 21 /c

  • a = 6.0635 (5) Å

  • b = 15.5187 (13) Å

  • c = 12.8009 (12) Å

  • β = 113.449 (6)°

  • V = 1105.06 (17) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 0.07 mm−1

  • T = 193 K

  • 0.49 × 0.45 × 0.27 mm

Data collection
  • Bruker SMART CCD diffractometer

  • 13517 measured reflections

  • 2637 independent reflections

  • 1711 reflections with I > 2σ(I)

  • Rint = 0.057

Refinement
  • R[F2 > 2σ(F2)] = 0.056

  • wR(F2) = 0.170

  • S = 1.02

  • 2637 reflections

  • 139 parameters

  • H-atom parameters constrained

  • Δρmax = 0.27 e Å−3

  • Δρmin = −0.22 e Å−3

Data collection: SMART (Bruker, 2006[Bruker (2006). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2006[Bruker (2006). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SIR97 (Altomare et al., 1999[Altomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115-119.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]); software used to prepare material for publication: PLATON.

Supporting information


Comment top

The title compound (Fig1.) is formed via base-catalyzed condensation of p-dimethylaminobenzaldehyde and tetramethylpyrazine. Monoclinic and triclinic crystals are obtained by crystallization from chloroform/methanol.

The monoclinic crystal is built from parallel layers (Fig. 2) with a distance of the mean planes of 3.5 Å indicating a π-π-interaction of neighbouring molecules. Perpendicular to the pyrazine-N are the nitrogen atoms of the dimethylamino groups of molecules in the lower and upper layer. Each molecule is connected to six neighbouring molecules via H-π-interactions with distances H–centroid of the π-system in the range of 2.27 - 2.88 Å. These CH-π-bonds connect pyrazin-methyl groups C4—H with anilines, and dimethylamino groups C14—H with pyrazines and C15—H with aniline rings. The molecules are planar, C14 shows the largest deviation (0.062 (2) A) from the plane defined by all 15 non H-atoms. The bond length C10—N13 of only 1.368 (2) Å is close to the bond lengths in the central heterocycle (N1—C2: 1.333 (2) Å; N1—C3: 1.353 (2) Å) indicating a strong electronic interaction of terminal donors and the central pyrazine acceptor.

The triclinic form contains two independent half-molecules which both are completed by inversion symmetry [1 - x, 1 - y, 1 - z and -x, 1 - y, 1 - z], drawn with different colours in the packing diagram of Fig. 3.

These molecules are arranged in layers with a distance of 3.7 Å and a tilt angle of 4 °. The centroids of the pyrazine rings of layers A and B are collinear but the molecules are twisted about about 60 °. The layers are connected via hydrogen bonds from C14—H (A) to the aniline ring (B). Crystal data are deposited under CCDC 807782.

Related literature top

The title compound was synthesized as a fundamental chromophore in a larger project focusing on solvatochromic and acidochromic dyes for sensing applications via one and two-photon excited fluorescence, see: Nemkovich et al. (2010); Schmitt et al. (2008); Detert & Schmitt (2006); Strehmel et al. (2003). Starting with 2,5-dimethylpyrazine, linear distyrylpyrazines had been prepared by acid-catalyzed condensations with benzaldehyde (Takahashi & Satake, 1952) as well as via Siegrist reaction with the anils of alkoxybenzaldehydes (Zerban, 1991).

Crystal data for the triclinic form have been deposited (CCDC 807782).

Experimental top

The title compound was prepared by adding potassium tert-butylate (1.50 g, 16.1 mmol) to a solution of tetramethylpyrazine (0.90 g, 6.70 mmol) and 4-dimethylaminobenzaldehyde (2.00 g, 13.41 mmol) in anhydrous DMF (25 ml). The mixture was stirred at 273 K under nitrogen until the aldehyde has been consumed (TLC). The mixture was diluted with water (75 ml) and the product extracted with chloroform, the solution dried with Na2SO4 and after evaporation of the solvent, the residue recrystallized from chloroform/methanol (1:1) to yield a mixture of block- and plate-shaped, dark red crystals. Yield: 1.42 g (54%), m.p.=522 K.

Refinement top

Hydrogen atoms attached to carbons were placed at calculated positions with C—H = 0.95 Å (aromatic) or 0.98–0.99 Å (sp3 C-atom). All H atoms were refined in the riding-model approximation with isotropic displacement parameters (set at 1.2–1.5 times of the Ueq of the parent atom).

Computing details top

Data collection: SMART (Bruker, 2006); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT (Bruker, 2006); 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 (Spek, 2009).

Figures top
[Figure 1] Fig. 1. View of compound I. Displacement ellipsoids are drawn at the 50% probability level. Inversion-related atoms [1 - x, 1 - y, 1 - z] are shown with suffix a.
[Figure 2] Fig. 2. A packing section of the monoclinic crystal form viewed down the a axis.
[Figure 3] Fig. 3. A packing section of the triclinic crystal form viewed down the a axis.
4-[2-(5-{2-[4-(dimethylamino)phenyl]ethenyl}-3,6-dimethylpyrazin-2-yl)ethenyl]- N,N-dimethylaniline top
Crystal data top
C26H30N4F(000) = 428
Mr = 398.54Dx = 1.198 Mg m3
Monoclinic, P21/cMelting point: 522 K
Hall symbol: -P 2ybcMo Kα radiation, λ = 0.71073 Å
a = 6.0635 (5) ÅCell parameters from 3217 reflections
b = 15.5187 (13) Åθ = 2.6–27°
c = 12.8009 (12) ŵ = 0.07 mm1
β = 113.449 (6)°T = 193 K
V = 1105.06 (17) Å3Block, orange
Z = 20.49 × 0.45 × 0.27 mm
Data collection top
Bruker SMART CCD
diffractometer
1711 reflections with I > 2σ(I)
Radiation source: sealed TubeRint = 0.057
Graphite monochromatorθmax = 28.0°, θmin = 2.2°
CCD scanh = 77
13517 measured reflectionsk = 2019
2637 independent reflectionsl = 1616
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.056Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.170H-atom parameters constrained
S = 1.02 w = 1/[σ2(Fo2) + (0.093P)2 + 0.1486P]
where P = (Fo2 + 2Fc2)/3
2637 reflections(Δ/σ)max = 0.001
139 parametersΔρmax = 0.27 e Å3
0 restraintsΔρmin = 0.22 e Å3
Crystal data top
C26H30N4V = 1105.06 (17) Å3
Mr = 398.54Z = 2
Monoclinic, P21/cMo Kα radiation
a = 6.0635 (5) ŵ = 0.07 mm1
b = 15.5187 (13) ÅT = 193 K
c = 12.8009 (12) Å0.49 × 0.45 × 0.27 mm
β = 113.449 (6)°
Data collection top
Bruker SMART CCD
diffractometer
1711 reflections with I > 2σ(I)
13517 measured reflectionsRint = 0.057
2637 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0560 restraints
wR(F2) = 0.170H-atom parameters constrained
S = 1.02Δρmax = 0.27 e Å3
2637 reflectionsΔρmin = 0.22 e Å3
139 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.3645 (2)0.52967 (9)0.55807 (11)0.0361 (4)
C20.3898 (3)0.44536 (10)0.54641 (13)0.0340 (4)
C30.4723 (3)0.58565 (10)0.51230 (13)0.0347 (4)
C40.2626 (3)0.38669 (11)0.59782 (16)0.0437 (5)
H4A0.38080.35920.66610.066*
H4B0.17500.34230.54240.066*
H4C0.14920.42030.61850.066*
C50.4434 (3)0.67746 (11)0.52817 (15)0.0374 (4)
H50.51380.71740.49430.045*
C60.3227 (3)0.70847 (11)0.58799 (14)0.0363 (4)
H60.25430.66660.62030.044*
C70.2832 (3)0.79779 (11)0.60981 (14)0.0347 (4)
C80.1390 (3)0.81714 (11)0.66978 (16)0.0424 (5)
H80.07130.77100.69590.051*
C90.0920 (3)0.90040 (11)0.69218 (15)0.0424 (5)
H90.00740.91010.73270.051*
C100.1880 (3)0.97122 (11)0.65634 (13)0.0352 (4)
C110.3336 (3)0.95248 (11)0.59606 (14)0.0374 (4)
H110.40190.99850.57000.045*
C120.3784 (3)0.86880 (11)0.57435 (14)0.0383 (4)
H120.47760.85890.53380.046*
N130.1460 (3)1.05436 (9)0.67883 (13)0.0443 (4)
C140.0132 (4)1.07191 (13)0.73601 (18)0.0524 (5)
H14A0.16651.04210.69620.079*
H14B0.04151.13410.73570.079*
H14C0.06101.05130.81480.079*
C150.2474 (3)1.12637 (12)0.64153 (16)0.0479 (5)
H15A0.42281.12070.67240.072*
H15B0.20441.18020.66880.072*
H15C0.18381.12700.55810.072*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0347 (8)0.0396 (8)0.0399 (8)0.0014 (6)0.0210 (6)0.0010 (6)
C20.0300 (8)0.0397 (9)0.0351 (9)0.0006 (6)0.0161 (7)0.0006 (7)
C30.0304 (8)0.0415 (10)0.0342 (9)0.0024 (6)0.0151 (7)0.0013 (7)
C40.0462 (10)0.0433 (10)0.0542 (11)0.0003 (8)0.0334 (9)0.0002 (8)
C50.0374 (9)0.0388 (9)0.0416 (10)0.0012 (7)0.0215 (8)0.0008 (7)
C60.0342 (9)0.0401 (9)0.0378 (9)0.0004 (7)0.0176 (8)0.0006 (7)
C70.0340 (9)0.0390 (9)0.0359 (9)0.0022 (6)0.0191 (7)0.0006 (7)
C80.0469 (10)0.0433 (10)0.0506 (11)0.0020 (7)0.0338 (9)0.0012 (8)
C90.0449 (10)0.0476 (11)0.0493 (11)0.0020 (7)0.0343 (9)0.0006 (8)
C100.0337 (9)0.0408 (10)0.0350 (9)0.0029 (7)0.0179 (7)0.0015 (7)
C110.0388 (9)0.0398 (9)0.0418 (10)0.0027 (7)0.0249 (8)0.0008 (7)
C120.0363 (9)0.0459 (10)0.0424 (10)0.0004 (7)0.0258 (8)0.0024 (8)
N130.0517 (9)0.0399 (9)0.0532 (9)0.0051 (6)0.0336 (8)0.0023 (7)
C140.0531 (12)0.0521 (11)0.0653 (13)0.0063 (9)0.0376 (11)0.0115 (10)
C150.0501 (11)0.0409 (11)0.0577 (12)0.0017 (8)0.0268 (10)0.0050 (8)
Geometric parameters (Å, º) top
N1—C21.333 (2)C8—H80.9500
N1—C31.353 (2)C9—C101.403 (2)
C2—C3i1.413 (2)C9—H90.9500
C2—C41.504 (2)C10—N131.368 (2)
C3—C2i1.413 (2)C10—C111.415 (2)
C3—C51.459 (2)C11—C121.377 (2)
C4—H4A0.9800C11—H110.9500
C4—H4B0.9800C12—H120.9500
C4—H4C0.9800N13—C151.445 (2)
C5—C61.341 (2)N13—C141.451 (2)
C5—H50.9500C14—H14A0.9800
C6—C71.453 (2)C14—H14B0.9800
C6—H60.9500C14—H14C0.9800
C7—C121.401 (2)C15—H15A0.9800
C7—C81.406 (2)C15—H15B0.9800
C8—C91.378 (2)C15—H15C0.9800
C2—N1—C3119.01 (14)C8—C9—H9119.4
N1—C2—C3i120.87 (15)C10—C9—H9119.4
N1—C2—C4116.32 (14)N13—C10—C9122.27 (15)
C3i—C2—C4122.81 (15)N13—C10—C11121.15 (15)
N1—C3—C2i120.12 (15)C9—C10—C11116.58 (15)
N1—C3—C5117.47 (14)C12—C11—C10121.31 (15)
C2i—C3—C5122.40 (15)C12—C11—H11119.3
C2—C4—H4A109.5C10—C11—H11119.3
C2—C4—H4B109.5C11—C12—C7122.44 (16)
H4A—C4—H4B109.5C11—C12—H12118.8
C2—C4—H4C109.5C7—C12—H12118.8
H4A—C4—H4C109.5C10—N13—C15121.39 (14)
H4B—C4—H4C109.5C10—N13—C14120.01 (15)
C6—C5—C3123.56 (16)C15—N13—C14118.53 (14)
C6—C5—H5118.2N13—C14—H14A109.5
C3—C5—H5118.2N13—C14—H14B109.5
C5—C6—C7128.43 (16)H14A—C14—H14B109.5
C5—C6—H6115.8N13—C14—H14C109.5
C7—C6—H6115.8H14A—C14—H14C109.5
C12—C7—C8115.78 (15)H14B—C14—H14C109.5
C12—C7—C6124.56 (15)N13—C15—H15A109.5
C8—C7—C6119.66 (15)N13—C15—H15B109.5
C9—C8—C7122.61 (15)H15A—C15—H15B109.5
C9—C8—H8118.7N13—C15—H15C109.5
C7—C8—H8118.7H15A—C15—H15C109.5
C8—C9—C10121.28 (15)H15B—C15—H15C109.5
C3—N1—C2—C3i0.3 (3)C8—C9—C10—N13179.19 (17)
C3—N1—C2—C4179.17 (14)C8—C9—C10—C110.3 (3)
C2—N1—C3—C2i0.3 (3)N13—C10—C11—C12179.28 (15)
C2—N1—C3—C5179.15 (14)C9—C10—C11—C120.2 (2)
N1—C3—C5—C62.0 (3)C10—C11—C12—C70.2 (3)
C2i—C3—C5—C6176.81 (17)C8—C7—C12—C110.3 (3)
C3—C5—C6—C7179.74 (15)C6—C7—C12—C11179.28 (15)
C5—C6—C7—C123.1 (3)C9—C10—N13—C15179.76 (16)
C5—C6—C7—C8176.42 (18)C11—C10—N13—C150.3 (3)
C12—C7—C8—C90.4 (3)C9—C10—N13—C143.5 (3)
C6—C7—C8—C9179.23 (16)C11—C10—N13—C14177.07 (16)
C7—C8—C9—C100.4 (3)
Symmetry code: (i) x+1, y+1, z+1.

Experimental details

Crystal data
Chemical formulaC26H30N4
Mr398.54
Crystal system, space groupMonoclinic, P21/c
Temperature (K)193
a, b, c (Å)6.0635 (5), 15.5187 (13), 12.8009 (12)
β (°) 113.449 (6)
V3)1105.06 (17)
Z2
Radiation typeMo Kα
µ (mm1)0.07
Crystal size (mm)0.49 × 0.45 × 0.27
Data collection
DiffractometerBruker SMART CCD
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
13517, 2637, 1711
Rint0.057
(sin θ/λ)max1)0.659
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.056, 0.170, 1.02
No. of reflections2637
No. of parameters139
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.27, 0.22

Computer programs: SMART (Bruker, 2006), SAINT (Bruker, 2006), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009).

 

Acknowledgements

The authors are grateful to the DFG for financial support.

References

First citationAltomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115–119.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationBruker (2006). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationDetert, H. & Schmitt, V. (2006). J. Phys. Org. Chem. 19, 603–607.  Web of Science CrossRef CAS Google Scholar
First citationNemkovich, N. A., Detert, H. & Schmitt, V. (2010). Chem. Phys. 378, 37–41.  Web of Science CrossRef CAS Google Scholar
First citationSchmitt, V., Glang, S., Preis, J. & Detert, H. (2008). Adv. Sci. Technol. 55, 36–41.  CrossRef CAS Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSpek, A. L. (2009). Acta Cryst. D65, 148–155.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationStrehmel, B., Sarker, A. M. & Detert, H. (2003). ChemPhysChem, 4, 249–259.  Web of Science CrossRef PubMed CAS Google Scholar
First citationTakahashi, T. & Satake, K. (1952). Yakugaku Zasshi, 8, 1188–1192 CAN 47:44597.  CAS Google Scholar
First citationZerban, G. (1991). PhD thesis, University of Mainz, Germany.  Google Scholar

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