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The title compound, C30H18N8, is a crystallographically centrosymmetric mol­ecule. The pyrazine ring makes dihedral angles of 43.6 (3) and 33.0 (2)° with the two independent pyridine rings, and the dihedral angle between the two pyridine rings is 58.3 (3)°. The favoured orientation of the pyridine rings is such that their N atoms face each other.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801005153/bt6028sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536801005153/bt6028Isup2.hkl
Contains datablock I

CCDC reference: 165638

Key indicators

  • Single-crystal X-ray study
  • T = 298 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.041
  • wR factor = 0.104
  • Data-to-parameter ratio = 11.8

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry




Comment top

Bridging polypyridyl ligands have been actively studied in recent years as building blocks for supramolecular assemblies (Hagrman et al., 1999; Leininger et al., 2000). Some of the polypyridyl compounds are of considerable interest because of their potential functionality of their metal complexes as photonic molecular devices (Eggleston et al., 1997; Miller et al., 1999) and DNA probes (Yam et al., 1995; Holmlin et al., 1999). Incorporating a ligand with two chelating sites into the coordination sphere allows systematic construction of large supramolecular assemblies capable of acting as antennae in energy-conversion schemes, where the photochemical and redox properties of the complexes are strongly dependent on the nature of the ligands (Waterland et al., 2000). Since the stereochemistry of such compounds is so useful in the rational design of new functional materials, we report herein the crystal structure of 2,3,7,8-tetrakis(2-pyridyl)pyrazino[2,3-g]quinoxaline, (I). In this structure, there is half a molecule in the asymmetric unit and the other half is inversion related.

A perspective view of the title compound including the atomic numbering scheme is shown in Fig. 1. It consists of a pyrazino[2,3-g]quinoxaline system substituted with four pyridine rings. The two independent pyridine rings are not coplanar with each other nor with the pyrazine ring due to steric clashes between the H atoms of the pyridine rings. The torsion angle between the C—C bonds connecting the pyridine rings to the pyrazine ring (C5—C6—C7—C8) is 19.4 (3)°. The pyrazine ring makes dihedral angles of 43.6 (3) and 33.0 (2)° with the two independent pyridine rings. The dihedral angle between the two pyridine rings is 58.3 (3)° and their N atoms face each other. In the central C6 ring and the pyrazine ring, the mean deviation of any atom from the best-fit planes describing them are 0.0046 (1) and 0.0369 (3) Å, respectively. Furthermore, all non-H atoms in the pyrazino[2,3-g]quinoxaline system lie in a rough plane: the mean deviation of any non-H atoms from the best-fit plane describing them is 0.0522 (2) Å. These distortions from planarity in the molecule are similar to its analogues (Rasmussen et al., 1990; Du et al., 2001). The C—N bond distances lie in the range 1.306 (3)–1.382 (2) Å and are remarkably shorter than normal C—N single bonds (1.47 Å; Sasada, 1984) and longer than the CN double-bond distance (1.28 Å; Wang et al., 1998) due to the π-electron repulsion of the system. The C—C bond distances are in the range 1.367 (4)–1.489 (3) Å and all the bond angles are about 120°, falling within normal limits. There are no hydrogen bonds or ππ-stacking interactions between different molecules in the unit cell.

Experimental top

The title compound was synthesized by the reaction of 1,2,4,5-benzenetetramine and 2,2'-pyridyl in a 1:2 molar ratio. Single crystals suitable for X-ray diffraction were obtained by slow diffusion of diethyl ether into a CH2Cl2/CH3OH solution of the compound. The product was characterized by NMR and mass spectrometry, giving results consistent with those in the literature (Rillema & Mack, 1982).

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SMART; data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1998).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) showing 30% probability displacement ellipsoids. H atoms have been omitted.
2,3,7,8-Tetrakis(2-pyridyl)pyrazino-[2,3-g]quinoxaline top
Crystal data top
C30H18N8F(000) = 508
Mr = 490.52Dx = 1.373 Mg m3
Monoclinic, P2/cMo Kα radiation, λ = 0.71073 Å
a = 15.061 (5) ÅCell parameters from 4465 reflections
b = 6.2184 (19) Åθ = 1.5–25.0°
c = 13.908 (4) ŵ = 0.09 mm1
β = 114.398 (5)°T = 298 K
V = 1186.3 (6) Å3Prism, yellow
Z = 20.20 × 0.20 × 0.15 mm
Data collection top
Bruker SMART 1000
diffractometer
1217 reflections with I > 2σ(I)
ω scansRint = 0.035
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
θmax = 25.0°
Tmin = 0.983, Tmax = 0.987h = 1717
4515 measured reflectionsk = 37
2046 independent reflectionsl = 1616
Refinement top
Refinement on F2 w = 1/[σ2(Fo2) + (0.0466P)2]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.041(Δ/σ)max = 0.008
wR(F2) = 0.104Δρmax = 0.16 e Å3
S = 0.94Δρmin = 0.15 e Å3
2046 reflectionsExtinction correction: SHELXL97
173 parametersExtinction coefficient: 0.0092 (15)
H-atom parameters constrained
Crystal data top
C30H18N8V = 1186.3 (6) Å3
Mr = 490.52Z = 2
Monoclinic, P2/cMo Kα radiation
a = 15.061 (5) ŵ = 0.09 mm1
b = 6.2184 (19) ÅT = 298 K
c = 13.908 (4) Å0.20 × 0.20 × 0.15 mm
β = 114.398 (5)°
Data collection top
Bruker SMART 1000
diffractometer
2046 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1217 reflections with I > 2σ(I)
Tmin = 0.983, Tmax = 0.987Rint = 0.035
4515 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.041173 parameters
wR(F2) = 0.104H-atom parameters constrained
S = 0.94Δρmax = 0.16 e Å3
2046 reflectionsΔρmin = 0.15 e Å3
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. Full-MATRIX

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.24555 (13)0.7240 (3)0.07158 (14)0.0461 (5)
N20.42174 (12)0.7179 (3)0.33148 (13)0.0422 (5)
N30.31210 (11)1.0697 (3)0.34939 (13)0.0409 (5)
N40.11787 (13)0.7647 (3)0.19029 (14)0.0488 (5)
C10.22019 (16)0.6088 (4)0.01714 (18)0.0504 (6)
H3A0.18160.67460.08080.060*
C20.24769 (18)0.4002 (5)0.0196 (2)0.0585 (7)
H2A0.22670.32590.08320.070*
C30.3069 (2)0.3017 (4)0.0735 (2)0.0620 (7)
H1A0.32670.15980.07410.074*
C40.33617 (17)0.4181 (4)0.16537 (18)0.0500 (6)
H4A0.37800.35770.22930.060*
C50.30255 (14)0.6264 (3)0.16148 (16)0.0376 (5)
C60.33458 (14)0.7584 (3)0.25939 (16)0.0378 (5)
C70.27509 (14)0.9293 (3)0.27320 (15)0.0364 (5)
C80.16811 (14)0.9489 (4)0.20992 (15)0.0386 (5)
C90.12431 (16)1.1480 (4)0.18140 (17)0.0501 (6)
H9A0.16141.27320.19800.060*
C100.02475 (17)1.1561 (4)0.1280 (2)0.0642 (7)
H12A0.00641.28780.10630.077*
C110.02855 (17)0.9704 (4)0.1066 (2)0.0655 (8)
H11A0.09610.97260.07060.079*
C120.02110 (17)0.7812 (4)0.1400 (2)0.0585 (7)
H10A0.01520.65500.12680.070*
C130.45943 (14)0.8533 (3)0.41707 (16)0.0387 (5)
C140.40723 (14)1.0411 (4)0.42217 (16)0.0378 (5)
C150.44856 (15)1.1859 (4)0.50402 (16)0.0427 (6)
H15A0.41481.30960.50630.051*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0385 (10)0.0572 (13)0.0387 (11)0.0036 (9)0.0120 (9)0.0078 (10)
N20.0356 (10)0.0469 (11)0.0392 (10)0.0004 (8)0.0105 (8)0.0086 (9)
N30.0320 (10)0.0466 (12)0.0383 (10)0.0033 (8)0.0087 (8)0.0039 (9)
N40.0370 (11)0.0488 (13)0.0573 (12)0.0049 (9)0.0159 (9)0.0058 (10)
C10.0370 (13)0.0727 (18)0.0404 (13)0.0069 (12)0.0149 (11)0.0096 (13)
C20.0544 (16)0.0723 (19)0.0537 (16)0.0207 (14)0.0273 (13)0.0262 (15)
C30.0794 (19)0.0459 (16)0.0686 (18)0.0044 (14)0.0386 (16)0.0163 (15)
C40.0574 (15)0.0424 (15)0.0500 (15)0.0001 (12)0.0220 (12)0.0011 (12)
C50.0321 (11)0.0428 (13)0.0385 (12)0.0057 (10)0.0151 (10)0.0057 (10)
C60.0325 (12)0.0426 (13)0.0370 (12)0.0015 (10)0.0131 (10)0.0021 (10)
C70.0347 (11)0.0401 (13)0.0323 (11)0.0012 (10)0.0118 (9)0.0004 (10)
C80.0324 (12)0.0439 (14)0.0370 (12)0.0006 (11)0.0119 (10)0.0041 (10)
C90.0357 (13)0.0449 (15)0.0590 (15)0.0013 (11)0.0090 (11)0.0030 (12)
C100.0413 (15)0.0538 (17)0.0803 (19)0.0088 (13)0.0078 (13)0.0002 (14)
C110.0305 (13)0.0638 (19)0.086 (2)0.0004 (13)0.0083 (12)0.0091 (15)
C120.0390 (15)0.0520 (16)0.0778 (18)0.0074 (12)0.0174 (13)0.0116 (14)
C130.0321 (12)0.0432 (13)0.0387 (12)0.0011 (10)0.0123 (10)0.0053 (10)
C140.0296 (11)0.0433 (13)0.0384 (12)0.0024 (10)0.0117 (10)0.0019 (10)
C150.0340 (12)0.0431 (14)0.0452 (13)0.0063 (10)0.0106 (10)0.0084 (11)
Geometric parameters (Å, º) top
N1—C51.335 (3)C5—C61.489 (3)
N1—C11.339 (3)C6—C71.453 (3)
N2—C61.306 (3)C7—C81.488 (3)
N2—C131.375 (2)C8—C91.382 (3)
N3—C71.307 (3)C9—C101.372 (3)
N3—C141.382 (2)C10—C111.367 (4)
N4—C121.335 (3)C11—C121.369 (3)
N4—C81.338 (3)C13—C15i1.388 (3)
C1—C21.367 (4)C13—C141.426 (3)
C2—C31.376 (3)C14—C151.382 (3)
C3—C41.374 (3)C15—C13i1.388 (3)
C4—C51.384 (3)
C5—N1—C1116.6 (2)C6—C7—C8123.91 (18)
C6—N2—C13118.11 (18)N4—C8—C9123.10 (19)
C7—N3—C14118.25 (18)N4—C8—C7115.70 (19)
C12—N4—C8116.4 (2)C9—C8—C7121.01 (19)
N1—C1—C2123.9 (2)C10—C9—C8118.3 (2)
C1—C2—C3119.0 (2)C11—C10—C9119.9 (2)
C4—C3—C2118.4 (2)C10—C11—C12117.6 (2)
C3—C4—C5119.0 (2)N4—C12—C11124.7 (2)
N1—C5—C4123.1 (2)N2—C13—C15i119.82 (19)
N1—C5—C6116.48 (19)N2—C13—C14120.39 (18)
C4—C5—C6120.3 (2)C15i—C13—C14119.69 (19)
N2—C6—C7121.26 (19)C15—C14—N3119.82 (19)
N2—C6—C5116.03 (19)C15—C14—C13120.31 (18)
C7—C6—C5122.65 (18)N3—C14—C13119.69 (19)
N3—C7—C6121.07 (19)C14—C15—C13i120.0 (2)
N3—C7—C8114.82 (18)
Symmetry code: (i) x+1, y+2, z+1.

Experimental details

Crystal data
Chemical formulaC30H18N8
Mr490.52
Crystal system, space groupMonoclinic, P2/c
Temperature (K)298
a, b, c (Å)15.061 (5), 6.2184 (19), 13.908 (4)
β (°) 114.398 (5)
V3)1186.3 (6)
Z2
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.20 × 0.20 × 0.15
Data collection
DiffractometerBruker SMART 1000
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.983, 0.987
No. of measured, independent and
observed [I > 2σ(I)] reflections
4515, 2046, 1217
Rint0.035
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.041, 0.104, 0.94
No. of reflections2046
No. of parameters173
No. of restraints?
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.16, 0.15

Computer programs: SMART (Bruker, 1998), SMART, SAINT (Bruker, 1998), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 1998).

Selected geometric parameters (Å, º) top
N1—C51.335 (3)N3—C71.307 (3)
N1—C11.339 (3)N3—C141.382 (2)
N2—C61.306 (3)N4—C121.335 (3)
N2—C131.375 (2)N4—C81.338 (3)
C5—N1—C1116.6 (2)N2—C6—C5116.03 (19)
C6—N2—C13118.11 (18)N3—C7—C8114.82 (18)
C7—N3—C14118.25 (18)N4—C8—C9123.10 (19)
C12—N4—C8116.4 (2)N4—C8—C7115.70 (19)
N1—C5—C6116.48 (19)C15—C14—N3119.82 (19)
 

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