An ortho-rhom-bic polymorph of pyrazino-[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile.

The title compound, C(16)H(6)N(6), is a polymorph of the previously reported structure [Kozlov & Goldberg (2008 ▶). Acta Cryst. C64, o498-o501]. Unlike the previously reported monoclinic polymorph (space group P2(1)/c, Z = 8), the title compound reveals ortho-rhom-bic symmetry (space group Pnma, Z = 4). The mol-ecule shows crystallographic mirror symmetry, while the previously reported structure exhibits two independent mol-ecules per asymmetric unit. In the title compound, adjacent mol-ecules are essentially parallel along the c axis and tend to be vertical along the b axis with dihedral angles of 72.02 (6)°. However, in the reported polymorph, the entire crystal structure shows an anti-parallel arrangement of adjacent columns related by inversion centers and the two independent mol-ecules are nearly parallel with a dihedral angle of 2.48 (6)°.

Related literature

For ligands based on 1,10-phenanthroline in coordination chemistry, see: Rabaca et al. (2008 ▶); Stephenson et al. (2008 ▶). For reports of the title compound in coordination chemistry, see: Kulkarni et al. (2004 ▶); Stephenson & Hardie (2006 ▶); Xiao et al. (2011 ▶); Xu et al. (2002 ▶). For examples of polymorphism, see: Demirtaş et al. (2011 ▶); Jiang et al. (2000 ▶); Okabe et al. (2001 ▶); Pan & Chen (2009 ▶); Ramos Silva et al. (2011 ▶); Thallapally et al. (2004 ▶). For the previously reported polymorph, see: Kozlov & Goldberg (2008 ▶). For related structures, see: Kozlov et al. (2008 ▶).

Experimental

Crystal data

C16H6N6

M = 282.27

Orthorhombic,

a = 14.1055 (13) Å

b = 16.3331 (14) Å

c = 5.2694 (4) Å

V = 1214.00 (18) Å3

Z = 4

Mo Kα radiation

μ = 0.10 mm−1

T = 293 K

0.45 × 0.30 × 0.26 mm

Data collection

Bruker SMART CCD area-detector diffractometer

Absorption correction: multi-scan (SADABS; Bruker, 2007 ▶) T min = 0.956, T max = 0.974

4543 measured reflections

1113 independent reflections

759 reflections with I > 2σ(I)

R int = 0.046

Refinement

R[F 2 > 2σ(F 2)] = 0.041

wR(F 2) = 0.119

S = 1.06

1113 reflections

100 parameters

H-atom parameters constrained

Δρmax = 0.20 e Å−3

Δρmin = −0.24 e Å−3

Data collection: SMART (Bruker, 2007 ▶); cell refinement: SAINT-Plus (Bruker, 2007 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶) and ORTEPIII (Burnett & Johnson, 1996 ▶); software used to prepare material for publication: SHELXTL.

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811047039/zq2127sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811047039/zq2127Isup2.hkl

Supplementary material file. DOI: 10.1107/S1600536811047039/zq2127Isup3.cml

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

C16H6N6	F(000) = 576
Mr = 282.27	Dx = 1.544 Mg m−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2n	Cell parameters from 1184 reflections
a = 14.1055 (13) Å	θ = 2.9–27.5°
b = 16.3331 (14) Å	µ = 0.10 mm−1
c = 5.2694 (4) Å	T = 293 K
V = 1214.00 (18) Å3	Block, yellow
Z = 4	0.45 × 0.30 × 0.26 mm

Bruker SMART CCD area-detector diffractometer	1113 independent reflections
Radiation source: fine-focus sealed tube	759 reflections with I > 2σ(I)
graphite	Rint = 0.046
phi and ω scans	θmax = 25.0°, θmin = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 2007)	h = −16→16
Tmin = 0.956, Tmax = 0.974	k = −19→7
4543 measured reflections	l = −6→6

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.041	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.119	H-atom parameters constrained
S = 1.06	w = 1/[σ2(Fo2) + (0.0556P)2 + 0.3018P] where P = (Fo2 + 2Fc2)/3
1113 reflections	(Δ/σ)max < 0.001
100 parameters	Δρmax = 0.20 e Å−3
0 restraints	Δρmin = −0.24 e Å−3

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
N1	0.56932 (11)	0.33317 (10)	−0.1078 (3)	0.0347 (5)
N2	0.77953 (11)	0.33585 (9)	0.6140 (3)	0.0322 (4)
N3	0.92249 (13)	0.37680 (13)	1.1146 (4)	0.0539 (6)
C1	0.61818 (12)	0.29508 (11)	0.0786 (3)	0.0279 (5)
C2	0.67134 (12)	0.33802 (11)	0.2603 (3)	0.0281 (5)
C3	0.67273 (13)	0.42373 (12)	0.2476 (4)	0.0349 (5)
H3	0.7060	0.4542	0.3673	0.042*
C4	0.62440 (14)	0.46176 (13)	0.0564 (4)	0.0381 (6)
H4	0.6249	0.5185	0.0422	0.046*
C5	0.57451 (13)	0.41428 (12)	−0.1161 (4)	0.0369 (5)
H5	0.5426	0.4410	−0.2463	0.044*
C6	0.72648 (12)	0.29328 (11)	0.4470 (3)	0.0285 (5)
C7	0.83106 (12)	0.29288 (12)	0.7773 (4)	0.0317 (5)
C8	0.88437 (14)	0.33918 (13)	0.9640 (4)	0.0372 (5)

	U11	U22	U33	U12	U13	U23
N1	0.0333 (9)	0.0368 (10)	0.0339 (10)	0.0021 (7)	−0.0025 (8)	0.0040 (8)
N2	0.0305 (9)	0.0357 (9)	0.0303 (9)	−0.0020 (7)	0.0014 (8)	−0.0007 (8)
N3	0.0476 (11)	0.0703 (14)	0.0437 (12)	−0.0084 (10)	−0.0041 (10)	−0.0142 (11)
C1	0.0249 (9)	0.0318 (10)	0.0271 (11)	0.0011 (8)	0.0041 (8)	0.0010 (9)
C2	0.0255 (9)	0.0291 (10)	0.0296 (11)	0.0002 (8)	0.0036 (8)	0.0018 (9)
C3	0.0335 (11)	0.0312 (10)	0.0401 (13)	−0.0031 (9)	−0.0007 (10)	−0.0031 (10)
C4	0.0353 (11)	0.0302 (10)	0.0488 (14)	0.0018 (9)	0.0026 (11)	0.0059 (10)
C5	0.0354 (11)	0.0370 (12)	0.0382 (12)	0.0052 (9)	−0.0005 (10)	0.0082 (10)
C6	0.0253 (9)	0.0319 (9)	0.0283 (10)	−0.0016 (8)	0.0028 (8)	−0.0029 (8)
C7	0.0264 (10)	0.0428 (11)	0.0261 (11)	−0.0027 (8)	0.0008 (9)	−0.0014 (9)
C8	0.0314 (11)	0.0480 (13)	0.0321 (12)	−0.0018 (9)	0.0013 (10)	−0.0013 (11)

N1—C5	1.327 (3)	C3—C4	1.366 (3)
N1—C1	1.352 (2)	C3—H3	0.9300
N2—C7	1.327 (2)	C4—C5	1.387 (3)
N2—C6	1.348 (2)	C4—H4	0.9300
N3—C8	1.138 (3)	C5—H5	0.9300
C1—C2	1.404 (2)	C6—C6i	1.414 (4)
C1—C1i	1.473 (4)	C7—C7i	1.401 (4)
C2—C3	1.402 (3)	C7—C8	1.451 (3)
C2—C6	1.451 (2)
C5—N1—C1	117.07 (17)	C3—C4—H4	120.6
C7—N2—C6	117.02 (16)	C5—C4—H4	120.6
N1—C1—C2	122.55 (17)	N1—C5—C4	124.37 (19)
N1—C1—C1i	117.41 (10)	N1—C5—H5	117.8
C2—C1—C1i	119.97 (11)	C4—C5—H5	117.8
C3—C2—C1	118.29 (17)	N2—C6—C6i	121.05 (10)
C3—C2—C6	121.85 (17)	N2—C6—C2	118.69 (16)
C1—C2—C6	119.80 (17)	C6i—C6—C2	120.23 (10)
C4—C3—C2	118.85 (18)	N2—C7—C7i	121.93 (10)
C4—C3—H3	120.6	N2—C7—C8	116.61 (17)
C2—C3—H3	120.6	C7i—C7—C8	121.41 (11)
C3—C4—C5	118.85 (18)	N3—C8—C7	177.0 (2)
C5—N1—C1—C2	1.0 (3)	C3—C4—C5—N1	0.7 (3)
C5—N1—C1—C1i	−175.87 (13)	C7—N2—C6—C6i	−0.18 (19)
N1—C1—C2—C3	0.5 (3)	C7—N2—C6—C2	−178.16 (15)
C1i—C1—C2—C3	177.37 (12)	C3—C2—C6—N2	0.7 (3)
N1—C1—C2—C6	−176.57 (15)	C1—C2—C6—N2	177.73 (15)
C1i—C1—C2—C6	0.26 (19)	C3—C2—C6—C6i	−177.26 (13)
C1—C2—C3—C4	−1.5 (3)	C1—C2—C6—C6i	−0.26 (19)
C6—C2—C3—C4	175.52 (17)	C6—N2—C7—C7i	0.18 (19)
C2—C3—C4—C5	1.0 (3)	C6—N2—C7—C8	−177.14 (15)
C1—N1—C5—C4	−1.7 (3)