5,6-Bis(2-pyridyl)-2,3-pyrazine­dicarbo­nitrile

The crystal structure of the title compound, C₁₆H₈N₆, contains two independent mol­ecules with no significant difference in their structures. The pyrazine ring makes dihedral angles of 36.7 (2) and 36.5 (3)° with the two pyridine rings in one mol­ecule, and 43.1 (2) and 38.4 (1)° in the other. The dihedral angles between the two pyridine rings are 58.2 (2) and 56.0 (2)°, respectively. The favoured orientation of the pyridine rings is such that their N atoms face each other.

S1. Comment

Bridging polypyridyl compounds have attracted great interest as building blocks for supramolecular assemblies (Scandola et al., 1992; Scott et al., 1999). Some of the polypyridyl ligands have been actively studied in recent years because of the potential functionality of their metal complexes as molecular devices (Nallas & Brewer, 1997; Brauns et al., 1997) and DNA probes (Yam et al., 1995; Holmin, et al., 1999). In the present paper, we report the synthesis and crystal structure of a new polypyridyl compound, 5,6-Bis(2-pyridyl)-2,3-pyrazinedicarbonitrile, (I). \sch

The title compound consists of a pyrazine ring substituted with two pyridine rings and two nitrile groups. The unit cell contains two symmetry-independent molecules without significant difference in this structure (Fig. 1). The two pyridine rings are not co-planar with each other or with the pyrazine ring due to the steric clashes between the H atoms in the pyridyl rings. The torsional angles between the carbon-carbon bonds connecting the pyridine rings to pyrazine ring (C7—C5—C6—C12 and C23—C21—C22—C28) are 18.8 (3) and 20.0 (4)° for the two molecules, respectively. In the pyrazine rings, the maximum deviation of any atom from the best-fit planes describing them are 0.0663 (2) and 0.0707 (1) Å. The pyrazine rings make dihedral angles of 36.7 (2) and 36.5 (3)° with the two pyridine rings in one molecule and 43.1 (2) versus 38.4 (1)° in the other. The dihedral angles of the pyridine rings are 58.2 (2) and 56.0 (2)°, and their N atoms face each other. These distortions from planarity in the molecue are similar to its analogues (Rasmussen et al., 1990). Both nitriles in each molecule are equivalent and typical N—C triple bonds. The other C—N bond distances lie in the range 1.329 (5)–1.352 (4) Å. The bond angles of C2—C1—N1, C18—C17—N7, C4—C3—N2 and C20—C19—N8 are close to 180°. There are no hydrogen bonds or π···π stacking interactions between different molecules.

Related literature

For related literature, see: Brauns et al. (1997); Nallas & Brewer (1997); Rasmussen et al. (1990); Scandola et al. (1992); Scott et al. (1999); Yam et al. (1995).

S2. Experimental

The title compound was synthesized by stirring 1:1 molar ratio 2,2'-pyridine (0.43 g, 2.0 mmol) and diaminomaleonitrile (0.22 g, 2.0 mmol) in the presence of several drops of acetic acid in ethanol solution (50 ml) under Ar atmosphere at reflux for ca 6 h. The solvent was concentrated in vacuo to afford a colorless solid which was purified by recrystallization from CH₂Cl₂/CH₃OH to obtain the single crystals suitable for X-ray diffraction. The title compound is not stable when exposed to air for a period of several months.

S3. Refinement

H atoms were located by geometry but their parameters were not refined.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Sheldrick, 1997).

Figures

Fig. 1. The molecular structure of (I) showing 30% probability displacement ellipsoids.

6,7-dicyano-2,3-di(2-pyridyl) pyrazine

Crystal data

C16H8N6	F(000) = 1168
Mr = 284.28	Dx = 1.322 Mg m^−3
Orthorhombic, Pna21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2n	Cell parameters from 10162 reflections
a = 16.996 (2) Å	θ = 2.0–25.0°
b = 8.1356 (11) Å	µ = 0.09 mm^−1
c = 20.660 (3) Å	T = 298 K
V = 2856.8 (7) Å^3	Prism, colorless
Z = 8	0.30 × 0.25 × 0.20 mm

Data collection

BRUKER SMART 1000 diffractometer	2589 reflections with I > 2.0σ(I)
ω scans	Rint = 0.037
Absorption correction: multi-scan [SAINT (Bruker, 1998) and SADABS (Sheldrick, 1997)]	θmax = 25.0°
Tmin = 0.975, Tmax = 0.983	h = −17→20
11285 measured reflections	k = −9→9
3743 independent reflections	l = −15→24

Refinement

Refinement on F^2	w = 1/[σ^2(Fo^2) + (0.0552P)^2] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.037	(Δ/σ)max = 0.003
wR(F^2) = 0.101	Δρmax = 0.13 e Å^−3
S = 0.98	Δρmin = −0.13 e Å^−3
3743 reflections	Extinction correction: SHELXL97 (Sheldrick, 1997)
398 parameters	Extinction coefficient: 0.0062 (6)
H-atom parameters constrained

Special details

Refinement. Full-MATRIX

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
N1	0.6311 (3)	0.2871 (6)	0.5624 (2)	0.1228 (16)
N2	0.4265 (2)	0.4290 (4)	0.48212 (19)	0.0961 (12)
N3	0.69013 (15)	0.3577 (3)	0.40500 (14)	0.0626 (8)
N4	0.54378 (14)	0.4089 (3)	0.34917 (13)	0.0543 (7)
N5	0.75346 (15)	0.5233 (4)	0.25727 (15)	0.0641 (8)
N6	0.63400 (14)	0.2649 (3)	0.21124 (16)	0.0581 (8)
C1	0.6296 (2)	0.3184 (5)	0.5085 (2)	0.0826 (12)
C2	0.6241 (2)	0.3566 (4)	0.44041 (16)	0.0602 (9)
C3	0.4825 (2)	0.4150 (4)	0.45223 (19)	0.0695 (10)
C4	0.55239 (19)	0.3941 (4)	0.41345 (17)	0.0565 (8)
C5	0.68305 (17)	0.3849 (4)	0.34128 (17)	0.0521 (8)
C6	0.60770 (16)	0.3947 (4)	0.31220 (16)	0.0481 (7)
C7	0.75663 (17)	0.4087 (4)	0.30460 (18)	0.0552 (8)
C8	0.82426 (17)	0.3206 (5)	0.3196 (2)	0.0687 (10)
C9	0.8906 (2)	0.3495 (6)	0.2825 (2)	0.0842 (13)
C10	0.8882 (2)	0.4633 (6)	0.2341 (2)	0.0854 (12)
C11	0.8191 (2)	0.5478 (5)	0.2228 (2)	0.0758 (11)
C12	0.59251 (15)	0.3803 (4)	0.24177 (15)	0.0462 (7)
C13	0.53403 (17)	0.4725 (4)	0.21271 (17)	0.0553 (8)
C14	0.5191 (2)	0.4492 (4)	0.14796 (18)	0.0682 (10)
C15	0.5612 (2)	0.3319 (5)	0.11529 (19)	0.0721 (10)
C16	0.6174 (2)	0.2445 (4)	0.1482 (2)	0.0680 (11)
H8A	0.8249	0.2450	0.3534	0.082*
H9A	0.9367	0.2915	0.2906	0.101*
H10A	0.9326	0.4838	0.2091	0.102*
H11A	0.8181	0.6251	0.1896	0.091*
H13A	0.5053	0.5488	0.2365	0.066*
H14A	0.4813	0.5118	0.1268	0.082*
H15A	0.5519	0.3120	0.0716	0.087*
H16A	0.6459	0.1659	0.1254	0.082*
N7	0.32586 (19)	0.5007 (5)	0.2028 (2)	0.0980 (12)
N8	0.1291 (3)	0.6880 (6)	0.1271 (2)	0.1095 (13)
N9	0.21888 (14)	0.5689 (3)	0.33991 (13)	0.0499 (6)
N10	0.07343 (14)	0.6470 (3)	0.28673 (13)	0.0544 (7)
N11	0.13306 (14)	0.7413 (3)	0.47788 (16)	0.0596 (8)
N12	0.00725 (15)	0.5052 (3)	0.43648 (15)	0.0605 (7)
C17	0.2744 (2)	0.5338 (4)	0.2354 (2)	0.0657 (9)
C18	0.20836 (18)	0.5781 (4)	0.27597 (16)	0.0500 (8)
C19	0.1323 (2)	0.6637 (5)	0.1814 (2)	0.0713 (10)
C20	0.13843 (18)	0.6301 (4)	0.25011 (16)	0.0536 (8)
C21	0.15692 (16)	0.6009 (3)	0.37760 (16)	0.0452 (7)
C22	0.08112 (16)	0.6230 (3)	0.35011 (15)	0.0464 (7)
C23	0.17320 (16)	0.6201 (4)	0.44774 (15)	0.0476 (7)
C24	0.22946 (17)	0.5271 (4)	0.47863 (16)	0.0546 (8)
C25	0.2434 (2)	0.5521 (4)	0.54376 (19)	0.0666 (9)
C26	0.2023 (2)	0.6735 (5)	0.57491 (18)	0.0719 (10)
C27	0.1481 (2)	0.7647 (5)	0.5403 (2)	0.0697 (10)
C28	0.00712 (16)	0.6148 (3)	0.38850 (16)	0.0495 (7)
C29	−0.05674 (17)	0.7104 (4)	0.37271 (19)	0.0613 (9)
C30	−0.1236 (2)	0.6952 (5)	0.4092 (2)	0.0777 (11)
C31	−0.1253 (2)	0.5862 (5)	0.4595 (2)	0.0763 (11)
C32	−0.0589 (2)	0.4935 (5)	0.4715 (2)	0.0733 (11)
H24A	0.2578	0.4481	0.4559	0.066*
H25A	0.2798	0.4881	0.5659	0.080*
H26A	0.2107	0.6942	0.6186	0.086*
H27A	0.1207	0.8470	0.5619	0.084*
H29A	−0.0546	0.7835	0.3381	0.074*
H30A	−0.1676	0.7587	0.3998	0.093*
H31A	−0.1701	0.5749	0.4850	0.092*
H32A	−0.0601	0.4190	0.5057	0.088*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.184 (4)	0.123 (4)	0.061 (3)	0.067 (3)	−0.003 (3)	−0.005 (3)
N2	0.102 (3)	0.108 (3)	0.078 (3)	0.026 (2)	0.027 (2)	0.008 (2)
N3	0.0676 (18)	0.0604 (17)	0.060 (2)	0.0130 (13)	−0.0128 (15)	−0.0103 (15)
N4	0.0552 (15)	0.0552 (17)	0.0525 (17)	0.0018 (12)	0.0019 (13)	−0.0031 (13)
N5	0.0617 (17)	0.0562 (17)	0.075 (2)	−0.0030 (13)	0.0013 (15)	−0.0028 (16)
N6	0.0630 (16)	0.0536 (17)	0.058 (2)	0.0043 (12)	0.0052 (14)	−0.0035 (14)
C1	0.109 (3)	0.089 (3)	0.050 (3)	0.042 (2)	−0.006 (2)	−0.009 (2)
C2	0.081 (2)	0.054 (2)	0.046 (2)	0.0150 (17)	−0.0040 (19)	−0.0069 (16)
C3	0.085 (3)	0.069 (2)	0.054 (2)	0.0158 (19)	0.009 (2)	0.0021 (18)
C4	0.069 (2)	0.0488 (19)	0.051 (2)	0.0060 (15)	0.0008 (18)	−0.0016 (16)
C5	0.056 (2)	0.0439 (18)	0.057 (2)	0.0070 (14)	−0.0095 (16)	−0.0065 (15)
C6	0.0497 (17)	0.0401 (17)	0.054 (2)	0.0011 (12)	−0.0002 (17)	−0.0016 (14)
C7	0.0484 (17)	0.0496 (18)	0.067 (2)	0.0017 (14)	−0.0094 (16)	−0.0139 (18)
C8	0.0524 (18)	0.072 (2)	0.081 (3)	0.0062 (17)	−0.0108 (19)	−0.018 (2)
C9	0.058 (2)	0.087 (3)	0.108 (4)	0.0123 (19)	−0.014 (2)	−0.031 (3)
C10	0.054 (2)	0.097 (3)	0.105 (4)	−0.010 (2)	0.009 (2)	−0.029 (3)
C11	0.077 (2)	0.069 (2)	0.081 (3)	−0.0122 (19)	0.010 (2)	−0.011 (2)
C12	0.0460 (16)	0.0449 (18)	0.0476 (19)	−0.0030 (13)	0.0003 (14)	−0.0015 (15)
C13	0.0525 (17)	0.0560 (19)	0.057 (2)	0.0052 (14)	−0.0033 (16)	−0.0022 (17)
C14	0.072 (2)	0.073 (3)	0.060 (2)	0.0043 (18)	−0.0154 (19)	−0.002 (2)
C15	0.091 (3)	0.075 (3)	0.050 (2)	−0.005 (2)	−0.001 (2)	−0.003 (2)
C16	0.085 (2)	0.061 (2)	0.058 (3)	0.0025 (19)	0.012 (2)	−0.0108 (18)
N7	0.092 (2)	0.113 (3)	0.089 (3)	0.0242 (19)	0.032 (2)	0.024 (2)
N8	0.157 (3)	0.118 (3)	0.053 (3)	0.035 (3)	−0.007 (2)	0.010 (2)
N9	0.0496 (14)	0.0511 (15)	0.0491 (17)	−0.0021 (11)	0.0030 (13)	0.0031 (12)
N10	0.0580 (16)	0.0525 (17)	0.0528 (18)	0.0046 (12)	−0.0068 (13)	0.0033 (14)
N11	0.0627 (15)	0.0593 (18)	0.057 (2)	0.0062 (14)	0.0005 (15)	−0.0079 (14)
N12	0.0568 (16)	0.0566 (16)	0.068 (2)	0.0021 (13)	0.0089 (14)	0.0012 (15)
C17	0.069 (2)	0.068 (2)	0.060 (2)	0.0060 (17)	0.011 (2)	0.0092 (19)
C18	0.0562 (18)	0.0436 (18)	0.050 (2)	−0.0006 (14)	0.0074 (16)	0.0016 (15)
C19	0.091 (3)	0.064 (2)	0.060 (3)	0.0135 (18)	−0.006 (2)	0.004 (2)
C20	0.062 (2)	0.0468 (18)	0.052 (2)	0.0019 (15)	−0.0012 (16)	0.0009 (15)
C21	0.0486 (16)	0.0392 (17)	0.0480 (19)	−0.0003 (13)	−0.0017 (16)	0.0038 (14)
C22	0.0476 (18)	0.0393 (17)	0.052 (2)	0.0005 (13)	−0.0011 (15)	−0.0008 (15)
C23	0.0454 (16)	0.0478 (18)	0.050 (2)	−0.0050 (14)	0.0025 (14)	0.0004 (15)
C24	0.0502 (17)	0.061 (2)	0.053 (2)	0.0005 (14)	−0.0015 (16)	−0.0012 (17)
C25	0.071 (2)	0.072 (2)	0.056 (2)	−0.0046 (18)	−0.0134 (19)	0.009 (2)
C26	0.084 (2)	0.085 (3)	0.047 (2)	−0.010 (2)	−0.001 (2)	−0.007 (2)
C27	0.077 (2)	0.073 (3)	0.059 (3)	0.0031 (19)	0.011 (2)	−0.012 (2)
C28	0.0487 (17)	0.0450 (17)	0.055 (2)	−0.0021 (14)	−0.0015 (15)	−0.0077 (16)
C29	0.0555 (17)	0.062 (2)	0.067 (2)	0.0095 (16)	−0.0095 (18)	−0.0049 (18)
C30	0.054 (2)	0.090 (3)	0.089 (3)	0.0125 (19)	−0.002 (2)	−0.022 (3)
C31	0.053 (2)	0.092 (3)	0.084 (3)	−0.0088 (19)	0.020 (2)	−0.030 (3)
C32	0.074 (2)	0.066 (2)	0.080 (3)	−0.0142 (19)	0.021 (2)	−0.006 (2)

Geometric parameters (Å, º)

N1—C1	1.143 (6)	C17—N7	1.137 (4)
N2—C3	1.140 (4)	C17—C18	1.446 (5)
N3—C2	1.340 (4)	C18—N9	1.335 (4)
N3—C5	1.340 (4)	C18—C20	1.370 (4)
N4—C6	1.333 (3)	C19—N8	1.140 (5)
N4—C4	1.342 (4)	C19—C20	1.449 (5)
N5—C11	1.339 (4)	C20—N10	1.346 (4)
N5—C7	1.352 (4)	C21—N9	1.335 (4)
N6—C12	1.333 (4)	C21—C22	1.419 (4)
N6—C16	1.342 (5)	C21—C23	1.484 (4)
C1—C2	1.444 (5)	C22—N10	1.330 (4)
C2—C4	1.374 (4)	C22—C28	1.488 (4)
C3—C4	1.443 (5)	C23—N11	1.351 (4)
C5—C6	1.417 (4)	C23—C24	1.377 (4)
C5—C7	1.475 (4)	C24—C25	1.381 (5)
C6—C12	1.483 (4)	C25—C26	1.371 (5)
C7—C8	1.390 (4)	C26—C27	1.381 (5)
C8—C9	1.384 (5)	C27—N11	1.329 (5)
C9—C10	1.363 (6)	C28—N12	1.333 (4)
C10—C11	1.382 (5)	C28—C29	1.375 (4)
C12—C13	1.382 (4)	C29—C30	1.369 (5)
C13—C14	1.375 (5)	C30—C31	1.366 (6)
C14—C15	1.371 (5)	C31—C32	1.380 (5)
C15—C16	1.372 (5)	C32—N12	1.341 (4)
C2—N3—C5	117.5 (3)	N7—C17—C18	178.9 (4)
C6—N4—C4	118.1 (3)	N9—C18—C20	121.3 (3)
C11—N5—C7	117.0 (3)	N9—C18—C17	117.1 (3)
C12—N6—C16	115.8 (3)	C20—C18—C17	121.6 (3)
N1—C1—C2	177.5 (5)	N8—C19—C20	178.4 (4)
N3—C2—C4	121.3 (3)	N10—C20—C18	121.6 (3)
N3—C2—C1	118.6 (3)	N10—C20—C19	118.2 (3)
C4—C2—C1	120.0 (3)	C18—C20—C19	120.1 (3)
N2—C3—C4	178.6 (4)	N9—C21—C22	120.5 (3)
N4—C4—C2	121.2 (3)	N9—C21—C23	116.3 (2)
N4—C4—C3	116.7 (3)	C22—C21—C23	123.1 (3)
C2—C4—C3	122.1 (3)	N10—C22—C21	120.1 (3)
N3—C5—C6	120.5 (3)	N10—C22—C28	116.6 (3)
N3—C5—C7	116.8 (3)	C21—C22—C28	123.2 (3)
C6—C5—C7	122.8 (3)	N11—C23—C24	122.6 (3)
N4—C6—C5	119.9 (3)	N11—C23—C21	115.6 (3)
N4—C6—C12	115.3 (2)	C24—C23—C21	121.6 (3)
C5—C6—C12	124.7 (3)	C23—C24—C25	119.3 (3)
N5—C7—C8	123.4 (3)	C26—C25—C24	118.4 (3)
N5—C7—C5	115.4 (3)	C25—C26—C27	118.9 (4)
C8—C7—C5	121.3 (4)	N11—C27—C26	123.6 (4)
C9—C8—C7	117.6 (4)	N12—C28—C29	123.8 (3)
C10—C9—C8	119.8 (4)	N12—C28—C22	115.1 (3)
C9—C10—C11	119.2 (4)	C29—C28—C22	121.0 (3)
N5—C11—C10	123.0 (4)	C30—C29—C28	118.2 (4)
N6—C12—C13	123.9 (3)	C31—C30—C29	119.7 (3)
N6—C12—C6	115.3 (3)	C30—C31—C32	118.3 (4)
C13—C12—C6	120.6 (3)	N12—C32—C31	123.3 (4)
C14—C13—C12	118.7 (3)	C18—N9—C21	117.4 (3)
C15—C14—C13	118.6 (3)	C22—N10—C20	117.2 (2)
C16—C15—C14	118.7 (4)	C27—N11—C23	117.1 (3)
N6—C16—C15	124.3 (3)	C28—N12—C32	116.6 (3)