Oxalic acid-pyridine-4-carbonitrile (1/2).

In the title compound, 2C(6)H(4)N(2)·C(2)H(2)O(4), the oxalic acid mol-ecule lies about an inversion center. The pyridine ring of the pyridine-4-carbonitrile mol-ecule is almost planar, the largest deviation from the least-squares plane being 0.006 (1) Å; the nitrile N atom deviates from this plane by 0.114 (1) Å. In the crystal, the oxalic acid mol-ecules and the pyridine-4-carbonitrile mol-ecules form stacks. Neighboring mol-ecules within the stacks are related by translation in the a direction, with inter-planar distances of 3.183 (1) and 3.331 (2) Å, respectively. Each oxalic acid mol-ecule forms strong O-H⋯N hydrogen bonds with two mol-ecules of pyridine-4-carbonitrile. Besides this, there are also weak C-H⋯O inter-actions.

Related literature

For the structures and ferroelectric properties of related compounds, see: Fu et al. (2011a ▶,b ▶,c ▶); Dai & Chen (2011 ▶); Xu et al. (2011 ▶); Zheng (2011 ▶). For standard bond lengths, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C6H4N2·0.5C2H2O4

M = 149.13

Triclinic,

a = 3.6842 (6) Å

b = 7.5816 (5) Å

c = 12.4511 (1) Å

α = 78.258 (1)°

β = 85.301 (1)°

γ = 82.547 (1)°

V = 337.08 (6) Å3

Z = 2

Mo Kα radiation

μ = 0.11 mm−1

T = 298 K

0.10 × 0.03 × 0.03 mm

Data collection

Rigaku SCXmini Mercury2 diffractometer

Absorption correction: multi-scan (CrystalClear; Rigaku, 2005 ▶) T min = 0.910, T max = 1.000

3634 measured reflections

1528 independent reflections

1268 reflections with I > 2σ(I)

R int = 0.024

Refinement

R[F 2 > 2σ(F 2)] = 0.036

wR(F 2) = 0.101

S = 1.04

1528 reflections

103 parameters

1 restraint

H atoms treated by a mixture of independent and constrained refinement

Δρmax = 0.46 e Å−3

Δρmin = −0.27 e Å−3

Data collection: CrystalClear (Rigaku, 2005 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812019137/yk2054sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812019137/yk2054Isup2.hkl

Supplementary material file. DOI: 10.1107/S1600536812019137/yk2054Isup3.cml

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

C6H4N2·0.5C2H2O4	Z = 2
Mr = 149.13	F(000) = 154
Triclinic, P1	Dx = 1.469 Mg m−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 3.6842 (6) Å	Cell parameters from 1528 reflections
b = 7.5816 (5) Å	θ = 2.9–27.5°
c = 12.4511 (1) Å	µ = 0.11 mm−1
α = 78.258 (1)°	T = 298 K
β = 85.301 (1)°	Block, colourless
γ = 82.547 (1)°	0.10 × 0.03 × 0.03 mm
V = 337.08 (6) Å3

Rigaku SCXmini Mercury2 diffractometer	1528 independent reflections
Radiation source: fine-focus sealed tube	1268 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.024
Detector resolution: 13.6612 pixels mm-1	θmax = 27.5°, θmin = 2.9°
ω scans CCD profile fitting	h = −4→4
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)	k = −9→9
Tmin = 0.910, Tmax = 1.000	l = −16→16
3634 measured reflections

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)] = 0.036	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.101	H atoms treated by a mixture of independent and constrained refinement
S = 1.04	w = 1/[σ2(Fo2) + (0.065P)2] where P = (Fo2 + 2Fc2)/3
1528 reflections	(Δ/σ)max < 0.001
103 parameters	Δρmax = 0.46 e Å−3
1 restraint	Δρmin = −0.27 e Å−3

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2sigma(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
O1	0.8019 (2)	0.10266 (10)	0.37597 (6)	0.0195 (2)
H1	0.753 (4)	0.2095 (6)	0.3465 (11)	0.029*
O2	1.0250 (2)	0.22804 (10)	0.50208 (6)	0.0196 (2)
N1	0.6137 (3)	0.43796 (12)	0.27800 (8)	0.0157 (2)
N2	0.1419 (3)	1.12502 (13)	0.09513 (8)	0.0207 (2)
C4	0.5310 (3)	0.75440 (15)	0.28546 (9)	0.0147 (3)
H4A	0.5545	0.8461	0.3231	0.018*
C1	0.4759 (3)	0.47781 (15)	0.17793 (9)	0.0158 (3)
H1A	0.4592	0.3835	0.1417	0.019*
C3	0.3848 (3)	0.79346 (14)	0.18234 (9)	0.0141 (3)
C5	0.6404 (3)	0.57355 (15)	0.33014 (9)	0.0152 (3)
H5A	0.7362	0.5455	0.3992	0.018*
C2	0.3578 (3)	0.65365 (14)	0.12654 (9)	0.0150 (3)
H2A	0.2638	0.6777	0.0573	0.018*
C6	0.2532 (3)	0.97886 (14)	0.13355 (9)	0.0161 (3)
C7	0.9557 (3)	0.09891 (14)	0.46785 (8)	0.0140 (3)

	U11	U22	U33	U12	U13	U23
O1	0.0299 (5)	0.0114 (4)	0.0174 (4)	−0.0004 (3)	−0.0102 (4)	−0.0010 (3)
O2	0.0269 (5)	0.0140 (4)	0.0189 (4)	−0.0026 (3)	−0.0066 (3)	−0.0033 (3)
N1	0.0164 (5)	0.0147 (5)	0.0158 (5)	−0.0021 (4)	−0.0022 (4)	−0.0020 (4)
N2	0.0244 (6)	0.0171 (5)	0.0210 (5)	−0.0016 (4)	−0.0067 (4)	−0.0029 (4)
C4	0.0142 (5)	0.0151 (5)	0.0159 (5)	−0.0027 (4)	−0.0002 (4)	−0.0049 (4)
C1	0.0169 (6)	0.0153 (5)	0.0164 (5)	−0.0030 (4)	−0.0017 (4)	−0.0048 (4)
C3	0.0118 (5)	0.0130 (5)	0.0167 (5)	−0.0018 (4)	−0.0004 (4)	−0.0011 (4)
C5	0.0157 (5)	0.0169 (6)	0.0131 (5)	−0.0027 (4)	−0.0025 (4)	−0.0019 (4)
C2	0.0156 (6)	0.0169 (6)	0.0126 (5)	−0.0025 (4)	−0.0023 (4)	−0.0024 (4)
C6	0.0162 (6)	0.0177 (6)	0.0155 (5)	−0.0043 (4)	−0.0014 (4)	−0.0042 (4)
C7	0.0144 (5)	0.0143 (5)	0.0131 (5)	−0.0010 (4)	−0.0012 (4)	−0.0024 (4)

O1—C7	1.3113 (12)	C4—H4A	0.9300
O1—H1	0.822 (2)	C1—C2	1.3871 (15)
O2—C7	1.2075 (13)	C1—H1A	0.9300
N1—C5	1.3403 (14)	C3—C2	1.3981 (15)
N1—C1	1.3462 (13)	C3—C6	1.4505 (14)
N2—C6	1.1503 (14)	C5—H5A	0.9300
C4—C5	1.3910 (15)	C2—H2A	0.9300
C4—C3	1.3940 (14)	C7—C7i	1.557 (2)
C7—O1—H1	107.8 (11)	N1—C5—C4	122.85 (10)
C5—N1—C1	118.83 (9)	N1—C5—H5A	118.6
C5—C4—C3	117.70 (10)	C4—C5—H5A	118.6
C5—C4—H4A	121.1	C1—C2—C3	117.75 (10)
C3—C4—H4A	121.1	C1—C2—H2A	121.1
N1—C1—C2	122.74 (10)	C3—C2—H2A	121.1
N1—C1—H1A	118.6	N2—C6—C3	178.67 (12)
C2—C1—H1A	118.6	O2—C7—O1	126.63 (10)
C4—C3—C2	120.13 (10)	O2—C7—C7i	121.93 (12)
C4—C3—C6	120.12 (9)	O1—C7—C7i	111.44 (11)
C2—C3—C6	119.74 (10)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N1	0.82 (1)	1.80 (1)	2.6173 (12)	176 (2)
C4—H4A···O1ii	0.93	2.48	3.3640 (13)	160

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯N1	0.82 (1)	1.80 (1)	2.6173 (12)	176 (2)
C4—H4A⋯O1i	0.93	2.48	3.3640 (13)	160

Symmetry code: (i) .