4-[N,N-Bis(2-cyano­ethyl)­amino]­pyridine

The title compound, 3,3'-(4-pyridyl­imino)­di­propane­nitrile, C₁₁H₁₂N₄, has a twofold axis and consists of a pyridine ring head and two cyano­ethyl tails, the three groups being linked by an N atom. The planar geometry around the amino N atom suggests conjugation with the [pi]-system of the pyridine ring. The mol­ecules are stacked in a layer structure via relatively weak to very weak intermolecular C-H...[pi] and C-H...N hydrogen-bond interactions.

S1. Comment

Hydrogen bonding is very important in determining the physical properties of materials, the conformation of biopolymers, the molecular packing and molecular recognition (Crabtree et al., 1998). Recently, more and more interest has concentrated on a series of new hydrogen-bonding interactions. These interactions are different from classical hydrogen bonding. The π-electrons, such as those of an aromatic ring and C—C or C—N multiple bonds, are shown to be able to act as weak proton acceptors (Atwood et al., 1991; Brammer et al., 1991; Shubina et al., 1997; Yao et al., 1997). It is well kown that 4-(N,N-dimethylamino)pyridine (DMAP) and its derivatives are efficient catalysts in many organic reactions (Höfle et al., 1978; Scriven, 1983; Steglich et al., 1969). As a derivative of DMAP, the title compound, (I), also has potential catalytic properties in some organic reactions (Huang et al., 1994). In this work, the X-ray crystal structure analysis of (I) has been carried out in order to investigate the intermolecular weak hydrogen-bonding interactions.

The title compound, (I), consists of a pyridine ring head and two cyanoethyl group tails (Fig. 1). Atoms N1, C3 and N2 lie on the twofold axis. The head and tails are all bonded to atom N2, which is not only in the plane of the pyridine ring, but also in the plane of the tails. The C1—C2—C3—N2 and N2—C4—C5—C6 torsion angles are 179.3 (1) and 179.0 (2)°, respectively. Similar to aminopyridines and their derivatives (Chao & Schempp et al., 1977; Ohms et al., 1983), the sum of bond angles around atom N2 is 360° (Table 1). The dihedral angle between the ring plane and the plane defined by atoms N2/C4/C4(2 − x, y, 1/2 − z) is 12.4 (2)°. The N2—C3 bond length [1.374 (3) Å] is about midway between those in 2-aminopyridine [1.351 (2) Å; Chao et al., 1975a] and 3-aminopyridine [1.384 (4) Å; Chao et al., 1975b]. This geometric conformation reflects the conjugation between the lone pair of N2 and the π-system of the pyridine ring (Chao & Schempp, 1977).

The molecules stack as a layer structure. Neighboring layers slide laterally from each other. Each layer is composed of many molecular chains. These parallel molecular chains extended along the b axis and all the molecules of a chain have the same head-to-tail orientation (Fig. 2). Adjacent chains have a different molecular orientation and they connected by C2—H2···N3(3/2 − x, 3/2 − y, −z) hydrogen bonds (Table 2). In these chains, adjacent molecules are also connected by C4—H4B···N1(x, y + 1, z) and C1—H1···N3(x, y − 1, z) hydrogen bonds (see Fig. 2). The nitrile groups also act as proton acceptors in C1—H1···Cg1(x, y − 1, z) and C1A—H1A···Cg1(2 − x, −1 + y, 1/2 − z), where Cg1 is the centre of the nitrile group. The geometry of this weak C—H···π hydrogen bond is similar to that observed in 2α-4'β-dihydroxy-2β,4'α-diethynylspiro[5.5]undec-2'-ene (Subramanian et al., 1996).

The pyridine ring planes are parallel to each other and the distance between adjacent layers is 3.687 (5) Å. This is greater than the separations observed for stacking interactions (3.3–3.6 Å; Glówka et al., 1999; Hunter et al., 1990). Neighboring layers are linked by a C5—H5A···N3(3/2 − x, −1/2 + y, 1/2 − z) hydrogen bond (see Fig.3), with a C···N distance of 3.686 (4) Å. Although this distance is longer than some hydrogen-bond lengths, it can still be considered a reasonable length for weak hydrogen bonding (Komasa et al., 1998; Taylor et al., 1982). There are other types of hydrogen bonding between adjacent layers, as shown in Fig. 3, where pyridine rings act as weak proton acceptors. One molecule in a layer bonds to two neighboring layers through a C4—H4A···Cg2(2 − x 1 − y −z) hydrogen bond, where Cg2 denotes the centroid of the pyridine ring. The C4···Cg2 distance and the angle at H4A are 3.550 (5) Å and 130.6°, respectively. The geometry of this hydrogen bond is similar to that observed in 3-O-benzyl-1,2-O-isopropylidene-5,6-dideoxy-α-D-ribo-hex-5-yno-1,4-furanose (Ciunik et al., 1998), N-(2,6-dimethylphenyl)-5-methylisoxazoe-3-carboxamide (Lutz et al., 1996) and 4-(4-H-1,2,4-triazol-4-yl)-2-Cl-phenylmethanimine (Ciunik et al., 2002).

S2. Experimental

4-Aminopyridine (8.0 g, 0.085 mol) and hydroquinone (0.02 g, 0.18 mmol) were added to acrylonitrile (50 ml). The reaction mixture was refluxed for 3 h, filtered and the solid product recrystallized from dimethylformamide (DMF). The white powder of (I) was filtered off, washed with CH₃OH, and dried in a vacuum desiccator (yield: 14.5 g, 85.2%). Colorless block-shaped single crystals of (I) (m.p. 481.1–482.7 K) were obtained by recrystallization from DMF. Elemental analysis calculated for C₁₁H₁₂N₄ (%): C 65.98, H 6.04, N 27.98; found: C 65.79, H 6.30, N 27.84. IR data (cm⁻¹): 2256 (s, CN), 1602 (s, C═N_py), 1521 (s, C═C_py). MS m/z: 201 (M+1, 100%).

S3. Refinement

The positions of all H atoms were fixed geometrically (C—H = 0.93 and 0.97 Å).

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SMART; data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXTL (Bruker, 2000); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The molecular structure of (I) with 30% probability displacement ellipsoids. Symmetry code: (A) 2 − x, y, 1/2 − z.
	Fig. 2. One crystal packing layer of (I). The moleculer chains are along the b axis. The H atoms not participating in hydrogen bonds have been omitted for clarity. Symmetry codes: (A) 2 − x, y, 1/2 − z; (B) 3/2 − x, 3/2 − y, −z; (') x, 1 + y, z.
	Fig. 3. (a) C—H···N hydrogen bond and (b) C—H···π hydrogen bond of adjacent layers viewed along the b axis. The H atoms not participating in hydrogen bonds have been omitted for clarity. Symmetry codes: (A) 2 − x, y, 1/2 − z; (A') x, 1 − y, 1/2 + z; (") 2 − x, 1 − y, −z.

3,3'-(4-pyridylimino)dipropanenitrile

Crystal data

C11H12N4	F(000) = 424
Mr = 200.25	Dx = 1.261 Mg m^−3
Monoclinic, C2/c	Melting point = 481.1–482.7 K
Hall symbol: -C 2yc	Mo Kα radiation, λ = 0.71073 Å
a = 15.355 (4) Å	Cell parameters from 756 reflections
b = 8.321 (2) Å	θ = 2.5–27.1°
c = 8.264 (2) Å	µ = 0.08 mm^−1
β = 92.12 (1)°	T = 293 K
V = 1055.2 (5) Å^3	Block, colorless
Z = 4	0.30 × 0.30 × 0.20 mm

Data collection

Bruker SMART APEX CCD area-detector diffractometer	820 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.026
Graphite monochromator	θmax = 25.0°, θmin = 2.7°
ϕ and ω scans	h = −15→18
2589 measured reflections	k = −8→9
922 independent reflections	l = −9→9

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.044	H-atom parameters constrained
wR(F^2) = 0.094	w = 1/[σ^2(Fo^2) + (0.02P)^2 + 1.2P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max = 0.012
922 reflections	Δρmax = 0.16 e Å^−3
71 parameters	Δρmin = −0.18 e Å^−3
0 restraints	Extinction correction: SHELXTL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.129 (5)

Special details

Refinement. The structure was solved by direct methods(Bruker, 2000) and successive difference Fourier syntheses. 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
C1	0.93500 (14)	0.2444 (2)	0.1855 (2)	0.0528 (5)
H1	0.8876	0.1887	0.1400	0.063*
C2	0.93152 (11)	0.4090 (2)	0.1800 (2)	0.0443 (5)
H2	0.8840	0.4607	0.1301	0.053*
C3	1.0000	0.4981 (3)	0.2500	0.0377 (6)
C4	0.93781 (11)	0.7541 (2)	0.1513 (2)	0.0429 (5)
H4A	0.9216	0.6920	0.0556	0.051*
H4B	0.9652	0.8524	0.1161	0.051*
C5	0.85573 (12)	0.7964 (2)	0.2406 (2)	0.0518 (5)
H5A	0.8270	0.6987	0.2739	0.062*
H5B	0.8714	0.8579	0.3371	0.062*
C6	0.79653 (12)	0.8899 (2)	0.1364 (3)	0.0501 (5)
N1	1.0000	0.1575 (3)	0.2500	0.0566 (7)
N2	1.0000	0.6631 (2)	0.2500	0.0429 (5)
N3	0.75322 (12)	0.9644 (2)	0.0517 (3)	0.0709 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0618 (12)	0.0431 (10)	0.0533 (11)	−0.0142 (9)	0.0000 (9)	−0.0055 (9)
C2	0.0409 (10)	0.0407 (10)	0.0508 (10)	−0.0019 (8)	−0.0052 (8)	−0.0014 (8)
C3	0.0368 (12)	0.0350 (13)	0.0412 (13)	0.000	0.0007 (10)	0.000
C4	0.0399 (10)	0.0364 (9)	0.0521 (10)	0.0014 (7)	−0.0022 (8)	0.0034 (8)
C5	0.0478 (11)	0.0496 (11)	0.0581 (11)	0.0068 (9)	0.0026 (9)	0.0042 (9)
C6	0.0379 (10)	0.0420 (10)	0.0701 (13)	0.0026 (8)	−0.0036 (9)	−0.0048 (9)
N1	0.0786 (17)	0.0354 (12)	0.0557 (14)	0.000	0.0020 (12)	0.000
N2	0.0382 (11)	0.0315 (10)	0.0580 (13)	0.000	−0.0110 (9)	0.000
N3	0.0537 (11)	0.0614 (11)	0.0961 (15)	0.0112 (9)	−0.0173 (10)	0.0018 (11)

Geometric parameters (Å, º)

C1—N1	1.328 (2)	C4—H4A	0.9700
C1—C2	1.371 (3)	C4—H4B	0.9700
C1—H1	0.9300	C5—C6	1.454 (3)
C2—C3	1.394 (2)	C5—H5A	0.9700
C2—H2	0.9300	C5—H5B	0.9700
C3—N2	1.374 (3)	C6—N3	1.132 (2)
C3—C2^i	1.394 (2)	N1—C1^i	1.328 (2)
C4—N2	1.4462 (19)	N2—C4^i	1.4462 (19)
C4—C5	1.525 (2)
N1—C1—C2	125.81 (19)	C5—C4—H4B	109.0
N1—C1—H1	117.1	H4A—C4—H4B	107.8
C2—C1—H1	117.1	C6—C5—C4	110.27 (16)
C1—C2—C3	119.27 (18)	C6—C5—H5A	109.6
C1—C2—H2	120.4	C4—C5—H5A	109.6
C3—C2—H2	120.4	C6—C5—H5B	109.6
N2—C3—C2^i	122.10 (11)	C4—C5—H5B	109.6
N2—C3—C2	122.10 (11)	H5A—C5—H5B	108.1
C2^i—C3—C2	115.8 (2)	N3—C6—C5	177.2 (2)
N2—C4—C5	112.85 (14)	C1^i—N1—C1	114.0 (2)
N2—C4—H4A	109.0	C3—N2—C4^i	121.54 (9)
C5—C4—H4A	109.0	C3—N2—C4	121.54 (9)
N2—C4—H4B	109.0	C4^i—N2—C4	116.92 (19)

Symmetry code: (i) −x+2, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···Cg1^ii	0.93	2.80	3.667 (5)	140
C1—H1···N3^ii	0.93	2.86	3.770 (5)	167
C2—H2···N3^iii	0.93	2.62	3.524 (3)	165
C4—H4A···Cg2^iv	0.97	2.84	3.550 (5)	131
C4—H4B···N1^v	0.97	2.81	3.576 (4)	136
C5—H5A···N3^vi	0.97	2.74	3.686 (4)	164

Symmetry codes: (ii) x, y−1, z; (iii) −x+3/2, −y+3/2, −z; (iv) −x+2, −y+1, −z; (v) x, y+1, z; (vi) −x+3/2, y−1/2, −z+1/2.