A centrosymmetric monoclinic polymorph of N¹,N⁴-bis­­(pyridin-3-yl­methyl­­idene)benzene-1,4-di­amine

The complete molecule of the title compound, C₁₈H₁₄N₄, is generated by the application of a centre of inversion. The dihedral angle between the central benzene ring and the pyridine ring is 31.88 (7)°. In the crystal, mol­ecules are stacked in columns along the c axis and several inter­molecular π–π inter­actions are present between the six-membered rings, the shortest centroid–centroid distance being 3.937 (2) Å. The structure reported herein represents a centrosymmetric polymorph of the previously reported non-centrosymmetric (P2₁) form [Kim et al. (2005). Bull. Korean Chem. Soc. 26, 892–898].

Related literature

For the crystal structure of N¹,N⁴-bis­(pyridin-3-yl­methyl­ene)benzene-1,4-diamine, see: Kim et al. (2005). For the crystal structure of N¹,N⁴-bis­(pyridin-2-yl­methyl­ene)benzene-1,4-diamine, see: Chanda et al. (2002); Ball et al. (2004).

Experimental

Crystal data

• C₁₈H₁₄N₄

• M_r = 286.33

• Monoclinic, P 2₁ /c

• a = 16.622 (6) Å

• b = 6.171 (2) Å

• c = 7.159 (2) Å

• β = 95.732 (8)°

• V = 730.6 (4) ų

• Z = 2

• Mo Kα radiation

• μ = 0.08 mm⁻¹

• T = 200 K

• 0.22 × 0.14 × 0.11 mm

Data collection

• Bruker SMART 1000 CCD diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2000) T_min = 0.825, T_max = 1.000

• 5128 measured reflections

• 1790 independent reflections

• 1027 reflections with I > 2σ(I)

• R_int = 0.049

Refinement

• R[F² > 2σ(F²)] = 0.053

• wR(F²) = 0.152

• S = 1.03

• 1790 reflections

• 100 parameters

• H-atom parameters constrained

• Δρ_max = 0.21 e Å⁻³

• Δρ_min = −0.24 e Å⁻³

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97.

Supporting information

S1. Comment

The title compound is a polydentate Schiff-base (Fig. 1), which can act as a monodentate or bis(monodentate) ligand, that is, one N atom or two N atoms of the pyridyl groups can coordinate to a metal ion or metal ions. The crystal structure of the this compound was previously reported in the non-centrosymmetric space group P2₁ (Kim et al., 2005). The centrosymmetric structure presented here is essentially the same as the published structure and represents a new monoclinic polymorph. In the present study the compound is isomorphous with the analogous compound N¹,N⁴-bis(pyridin-2-ylmethylene)benzene-1,4-diamine (Chanda et al., 2002; Ball et al., 2004).

The asymmetric unit of the title molecule contains one half of the formula unit (Fig. 1); a centre of inversion is located in the midpoint of the compound, and therefore the two pyridyl rings are exactly parallel. The dihedral angle between the central benzene ring and the pyridine ring is 31.88 (7) °. The N2—C6/7 bond lengths and the C6—N2—C7 bond angle indicate that the imino N2 atom is sp²-hybridized [d(N2═C6) = 1.283 (2) Å and d(N2—C7) = 1.429 (2) Å; <C6—N2—C7 = 119.0 (2) °]. In the crystal structure, the molecules are stacked in columns along the c axis and several intermolecular π-π interactions are present between the six-membered rings, with a shortest centroid-centroid distance being 3.937 (2) Å (Fig. 2).

Related literature

For the crystal structure of N¹,N⁴-bis(pyridin-3-ylmethylene)benzene-1,4-diamine, see: Kim et al. (2005). For the crystal structure of N¹,N⁴-bis(pyridin-2-ylmethylene)benzene-1,4-diamine, see: Chanda et al. (2002); Ball et al. (2004).

S2. Experimental

1,4-Phenylenediamine (1.0812 g, 9.998 mmol) and 3-pyridinecarboxaldehyde (2.1447 g, 20.023 mmol) in CH₃CN (30 ml) were stirred for 3 h at room temperature. The precipitate was then separated by filtration, washed with CH₃CN and ether, and dried under vacuum, to give a yellow powder (1.8899 g). Crystals suitable for X-ray analysis were obtained by slow evaporation from its ethylacetate solution.

S3. Refinement

H atoms were positioned geometrically and allowed to ride on their respective parent atoms [C—H = 0.95 Å and U_iso(H) = 1.2U_eq(C)].

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The structure of the title compound, with displacement ellipsoids drawn at the 50% probability level; H atoms are shown as small circles of arbitrary radius. Unlabelled atoms are related by the symmetry transformation: -x, -y, 1 - z.
	Fig. 2. View of the unit-cell contents of the title compound.

N¹,N⁴-bis(pyridin-3-ylmethylidene)benzene-1,4-diamine

Crystal data

C18H14N4	F(000) = 300
Mr = 286.33	Dx = 1.301 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 1327 reflections
a = 16.622 (6) Å	θ = 2.5–28.2°
b = 6.171 (2) Å	µ = 0.08 mm^−1
c = 7.159 (2) Å	T = 200 K
β = 95.732 (8)°	Plate, yellow
V = 730.6 (4) Å^3	0.22 × 0.14 × 0.11 mm
Z = 2

Data collection

Bruker SMART 1000 CCD diffractometer	1790 independent reflections
Radiation source: fine-focus sealed tube	1027 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.049
ϕ and ω scans	θmax = 28.3°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Bruker, 2000)	h = −22→19
Tmin = 0.825, Tmax = 1.000	k = −8→8
5128 measured reflections	l = −8→9

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.053	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.152	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.064P)^2 + 0.0036P] where P = (Fo^2 + 2Fc^2)/3
1790 reflections	(Δ/σ)max < 0.001
100 parameters	Δρmax = 0.21 e Å^−3
0 restraints	Δρmin = −0.24 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
N1	0.40327 (10)	0.2126 (3)	0.3182 (2)	0.0434 (5)
N2	0.16109 (9)	0.0893 (2)	0.4230 (2)	0.0296 (4)
C1	0.32643 (12)	0.1772 (3)	0.3548 (3)	0.0374 (5)
H1	0.3091	0.0310	0.3622	0.045*
C2	0.27031 (11)	0.3394 (3)	0.3825 (3)	0.0298 (5)
C3	0.29604 (12)	0.5530 (3)	0.3732 (3)	0.0426 (6)
H3	0.2602	0.6690	0.3922	0.051*
C4	0.37490 (13)	0.5940 (3)	0.3356 (3)	0.0501 (6)
H4	0.3938	0.7387	0.3282	0.060*
C5	0.42572 (13)	0.4208 (3)	0.3092 (3)	0.0439 (6)
H5	0.4795	0.4514	0.2831	0.053*
C6	0.18734 (11)	0.2849 (3)	0.4232 (3)	0.0300 (5)
H6	0.1520	0.3990	0.4507	0.036*
C7	0.07963 (11)	0.0508 (3)	0.4617 (2)	0.0264 (4)
C8	0.06382 (11)	−0.1381 (3)	0.5601 (2)	0.0293 (5)
H8	0.1070	−0.2333	0.6006	0.035*
C9	0.01465 (11)	0.1882 (3)	0.4004 (2)	0.0286 (4)
H9	0.0243	0.3158	0.3318	0.034*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0308 (10)	0.0441 (11)	0.0568 (12)	0.0014 (8)	0.0123 (8)	0.0005 (8)
N2	0.0263 (9)	0.0297 (9)	0.0338 (8)	−0.0027 (7)	0.0080 (6)	0.0001 (7)
C1	0.0320 (12)	0.0327 (11)	0.0488 (12)	−0.0006 (8)	0.0108 (9)	0.0010 (9)
C2	0.0266 (10)	0.0296 (10)	0.0337 (10)	−0.0018 (8)	0.0057 (8)	−0.0005 (8)
C3	0.0331 (12)	0.0279 (11)	0.0688 (14)	0.0000 (9)	0.0149 (10)	−0.0012 (10)
C4	0.0388 (13)	0.0348 (12)	0.0790 (17)	−0.0103 (10)	0.0176 (11)	0.0000 (11)
C5	0.0288 (11)	0.0456 (13)	0.0586 (13)	−0.0069 (10)	0.0113 (10)	0.0003 (10)
C6	0.0261 (10)	0.0307 (11)	0.0338 (10)	0.0001 (8)	0.0060 (8)	−0.0016 (8)
C7	0.0248 (10)	0.0278 (10)	0.0274 (9)	−0.0017 (7)	0.0063 (7)	−0.0026 (7)
C8	0.0273 (10)	0.0284 (10)	0.0325 (10)	0.0003 (8)	0.0038 (8)	0.0007 (8)
C9	0.0310 (11)	0.0264 (10)	0.0288 (9)	−0.0011 (8)	0.0048 (8)	0.0018 (7)

Geometric parameters (Å, º)

N1—C5	1.341 (3)	C4—C5	1.387 (3)
N1—C1	1.347 (2)	C4—H4	0.9500
N2—C6	1.283 (2)	C5—H5	0.9500
N2—C7	1.429 (2)	C6—H6	0.9500
C1—C2	1.396 (3)	C7—C8	1.401 (2)
C1—H1	0.9500	C7—C9	1.408 (3)
C2—C3	1.389 (3)	C8—C9^i	1.396 (3)
C2—C6	1.476 (3)	C8—H8	0.9500
C3—C4	1.387 (3)	C9—C8^i	1.396 (3)
C3—H3	0.9500	C9—H9	0.9500
C5—N1—C1	116.01 (18)	N1—C5—H5	118.1
C6—N2—C7	118.98 (16)	C4—C5—H5	118.1
N1—C1—C2	124.86 (18)	N2—C6—C2	122.54 (17)
N1—C1—H1	117.6	N2—C6—H6	118.7
C2—C1—H1	117.6	C2—C6—H6	118.7
C3—C2—C1	117.39 (18)	C8—C7—C9	118.75 (16)
C3—C2—C6	121.57 (17)	C8—C7—N2	117.70 (16)
C1—C2—C6	121.03 (17)	C9—C7—N2	123.50 (16)
C4—C3—C2	118.94 (19)	C9^i—C8—C7	120.79 (16)
C4—C3—H3	120.5	C9^i—C8—H8	119.6
C2—C3—H3	120.5	C7—C8—H8	119.6
C5—C4—C3	119.1 (2)	C8^i—C9—C7	120.45 (17)
C5—C4—H4	120.5	C8^i—C9—H9	119.8
C3—C4—H4	120.5	C7—C9—H9	119.8
N1—C5—C4	123.7 (2)
C5—N1—C1—C2	0.2 (3)	C3—C2—C6—N2	176.31 (18)
N1—C1—C2—C3	−0.5 (3)	C1—C2—C6—N2	−4.7 (3)
N1—C1—C2—C6	−179.58 (18)	C6—N2—C7—C8	−145.41 (17)
C1—C2—C3—C4	0.5 (3)	C6—N2—C7—C9	37.0 (2)
C6—C2—C3—C4	179.57 (19)	C9—C7—C8—C9^i	−1.0 (3)
C2—C3—C4—C5	−0.2 (3)	N2—C7—C8—C9^i	−178.72 (16)
C1—N1—C5—C4	0.2 (3)	C8—C7—C9—C8^i	1.0 (3)
C3—C4—C5—N1	−0.2 (4)	N2—C7—C9—C8^i	178.58 (16)
C7—N2—C6—C2	−179.26 (16)

Symmetry code: (i) −x, −y, −z+1.