2,3-Bis(4-nitro­benzyl­thio)­maleo­nitrile

The maleo­nitrile moiety of the title compound, (2Z)-2,3-bis­[(4-nitro­benzyl)­sulfanyl]­but-2-ene­di­nitrile, C₁₈H₁₂N₄O₄S₂, is almost planar. The two benzene rings are nearly parallel to each other and perpendicular to the maleo­nitrile plane. Intermolecular S...S and [pi]-[pi] interactions are observed in the crystal structure.

S1. Comment

New materials with useful properties (e.g. catalytic properties) may be afforded by infinite networks constructed from building blocks of various connectivities and geometries (Venkataraman et al., 1995; Fujita et al., 1994). Generally, the building blocks are ligands either with polydentate or with groups which can be combined by weak interactions, namely hydrogen-bond, S···S or π–π interactions. Maleonitrile–dithiacrown ethers are a class of polydentate ligand, whose S and nitrile N atoms are capable of bonding to metals, thus allowing the construction of self-assemblying materials with new properties (Drexler et al., 1999) and, as a result of this, they have attracted the interest of chemists. Maleonitrile–dithioethers, on the contrary, have been studied relatively little and they are expected to construct infinite network strutures incombination with transition metals. We have recently synthesized the title compound (I), which can act as a tetradentate ligand. The nitro group is capable of acting as a hydrogen-bond acceptor and forming hydrogen bonds with hydrogen-bond donors. intermolecular π–π interactions are also possible and the title compound is therefore a potential supramolecular building block.

The molecular structure of (I) is shown in Fig. 1. The maleonitrile moiety is almost planar, and the bond lengths and angles are consistent with those of an analogous compound (Spannenberg et al., 1996). It is worth noting that the average C–S bond length linking to maleonitrile [1.750 (2) Å] is shorter than that [1.820 (2) Å] linking to benzyl. This arises from the p–π conjugation effect between the S atom and conjugated maleonitrile system. The two benzene rings adopt conformations pointing away from the maleonitrile moiety, with a dihedral angle of 7.5 (3)° between them, almost parallel to one another, and nearly perpendicular to the maleonitrile plane; the dihedral angles between the benzene rings and maleonitrile plane are 88.6 (3) and 88.1 (3)°. The intramolecular S1···S2 distance is 3.110 (2) Å and the intermolecular S2···S2(-x + 1/2, −y + 1/2, −z) distance is 3.272 (2) Å, which is shorter than that of the dmit derivative 4,5-(2-hydroxypropylenedithio)-1,3-dithiolethione (Marshallsay et al., 1993). An intermolecular π–π interaction occurs between the C13–C18 and C13–C18(-x, y, 1/2 − z) benzene rings. For the overlap pair of benzene rings, the centroid–centroid distance is 4.086 (2) Å (Spek, 1990), the shortest atom–atom distance is 3.577 (2) Å, being larger than the distance of 3.48 Å in the TCNQ complex (Nakasuji et al., 1987), and the dihedral angle between the two benzene rings is 13.2 (3)°. Infinite molecular chains are formed through intermolecular S···S and π–π interactions (Fig. 2).

S2. Experimental

The title compound was prepared by refluxing of a 2:1 molar ratio of 4-nitrobenzyl chloride and disodium maleonitriledithiolate in methanol. The precipitated product was filtered off, washed with methanol and dried under vacuum. Yellow crystals were recrystallized from an acetone–n-butanol solution of the compound (m.p. 419–421 K).

S3. Refinement

The H atoms were placed in geometrically calculated positions (C—H = 0.93 Å and N—H = 0.86 Å), with U_eq(H) = 1.2U_eq(parent atom).

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: CAD-4 Software; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); 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 the title compound. Displacement ellipsoids are shown at the 30% probability level.
	Fig. 2. View of the one-dimensional array formed by S···S and π–π interactions in the structure of (I).

Bis(4-nitrobenzyl)maleonitriledithioether

Crystal data

C18H12N4O4S2	F(000) = 1696
Mr = 412.44	Dx = 1.491 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 29.456 (6) Å	Cell parameters from 25 reflections
b = 15.440 (3) Å	θ = 1.7–8.8°
c = 8.1900 (16) Å	µ = 0.32 mm^−1
β = 99.52 (3)°	T = 293 K
V = 3673.6 (13) Å^3	Block, yellow
Z = 8	0.32 × 0.26 × 0.24 mm

Data collection

FR590 CAD-4 diffractometer	Rint = 0.016
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 1.4°
Graphite monochromator	h = −34→34
2θ/ω scans	k = 0→18
3491 measured reflections	l = 0→9
3237 independent reflections	3 standard reflections every 97 reflections
2227 reflections with I > 2σ(I)	intensity decay: 0.0%

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)] = 0.033	H-atom parameters constrained
wR(F^2) = 0.100	w = 1/[σ^2(Fo^2) + (0.0454P)^2 + 2.8648P] where P = (Fo^2 + 2Fc^2)/3
S = 1.01	(Δ/σ)max < 0.001
3237 reflections	Δρmax = 0.16 e Å^−3
254 parameters	Δρmin = −0.18 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0017 (2)

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
S1	0.13345 (2)	0.32203 (4)	0.11857 (8)	0.05237 (19)
S2	0.20796 (2)	0.30507 (4)	−0.10797 (8)	0.0524 (2)
N2	0.33696 (8)	0.65987 (15)	0.0285 (3)	0.0594 (6)
C15	0.03974 (8)	0.27761 (15)	0.0872 (3)	0.0463 (5)
C8	0.27203 (7)	0.43007 (14)	−0.1641 (3)	0.0430 (5)
O4	0.37613 (8)	0.65487 (15)	0.1055 (3)	0.0851 (7)
C5	0.15820 (8)	0.36628 (14)	−0.1722 (3)	0.0445 (5)
C6	0.24889 (8)	0.34788 (15)	−0.2312 (3)	0.0488 (6)
H6A	0.2723	0.3044	−0.2378	0.059*
H6B	0.2329	0.3585	−0.3428	0.059*
C3	0.08543 (8)	0.42297 (15)	−0.1286 (3)	0.0543 (6)
O2	−0.10169 (7)	0.16278 (16)	−0.2452 (3)	0.0858 (7)
C11	0.31496 (8)	0.57963 (15)	−0.0407 (3)	0.0461 (5)
C17	0.00946 (9)	0.13808 (17)	−0.0063 (3)	0.0602 (7)
H17A	0.0128	0.0783	−0.0128	0.072*
C14	−0.00122 (8)	0.31492 (17)	0.0138 (3)	0.0569 (6)
H14A	−0.0051	0.3745	0.0214	0.068*
C2	0.12549 (7)	0.37206 (14)	−0.0749 (3)	0.0439 (5)
N4	0.14756 (9)	0.43232 (16)	−0.4637 (3)	0.0747 (7)
O3	0.31547 (8)	0.72727 (13)	0.0082 (3)	0.0828 (6)
C10	0.27351 (9)	0.58553 (16)	−0.1444 (3)	0.0550 (6)
H10A	0.2600	0.6391	−0.1720	0.066*
C18	−0.03070 (8)	0.17816 (17)	−0.0790 (3)	0.0519 (6)
C12	0.33593 (8)	0.50177 (16)	0.0031 (3)	0.0542 (6)
H12A	0.3642	0.4994	0.0729	0.065*
C4	0.15138 (8)	0.40423 (15)	−0.3338 (3)	0.0525 (6)
C9	0.25237 (8)	0.51031 (15)	−0.2068 (3)	0.0533 (6)
H9A	0.2245	0.5133	−0.2787	0.064*
C16	0.04443 (9)	0.18847 (16)	0.0759 (3)	0.0572 (6)
H16A	0.0717	0.1623	0.1248	0.069*
N1	−0.06777 (8)	0.12568 (18)	−0.1724 (3)	0.0685 (6)
C1	0.07751 (8)	0.33186 (17)	0.1826 (3)	0.0552 (6)
H1A	0.0807	0.3163	0.2987	0.066*
H1B	0.0681	0.3921	0.1727	0.066*
C13	−0.03643 (8)	0.26564 (17)	−0.0704 (3)	0.0582 (7)
H13A	−0.0637	0.2915	−0.1206	0.070*
N3	0.05417 (8)	0.46546 (16)	−0.1708 (4)	0.0817 (8)
C7	0.31398 (8)	0.42717 (16)	−0.0592 (3)	0.0512 (6)
H7A	0.3276	0.3738	−0.0302	0.061*
O1	−0.06291 (8)	0.04733 (16)	−0.1738 (3)	0.1020 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0429 (3)	0.0578 (4)	0.0539 (4)	0.0008 (3)	0.0008 (3)	0.0086 (3)
S2	0.0425 (3)	0.0503 (4)	0.0631 (4)	0.0028 (3)	0.0051 (3)	0.0198 (3)
N2	0.0704 (15)	0.0600 (14)	0.0465 (12)	−0.0160 (12)	0.0059 (11)	0.0006 (10)
C15	0.0425 (13)	0.0510 (14)	0.0463 (13)	0.0020 (10)	0.0098 (10)	0.0001 (11)
C8	0.0436 (12)	0.0444 (13)	0.0426 (12)	−0.0009 (10)	0.0121 (10)	0.0035 (10)
O4	0.0779 (14)	0.0895 (16)	0.0780 (14)	−0.0237 (12)	−0.0162 (12)	−0.0093 (12)
C5	0.0444 (12)	0.0353 (11)	0.0493 (14)	−0.0058 (10)	−0.0057 (10)	0.0070 (10)
C6	0.0493 (13)	0.0433 (13)	0.0546 (14)	−0.0045 (10)	0.0106 (11)	0.0010 (11)
C3	0.0415 (14)	0.0429 (13)	0.0733 (17)	−0.0068 (11)	−0.0053 (12)	0.0084 (12)
O2	0.0534 (12)	0.1146 (18)	0.0803 (14)	−0.0097 (12)	−0.0156 (10)	0.0112 (13)
C11	0.0513 (13)	0.0462 (13)	0.0409 (13)	−0.0061 (11)	0.0076 (10)	0.0017 (10)
C17	0.0582 (16)	0.0462 (14)	0.0714 (17)	0.0000 (12)	−0.0037 (13)	0.0032 (13)
C14	0.0503 (14)	0.0485 (14)	0.0737 (17)	0.0077 (12)	0.0151 (13)	0.0065 (13)
C2	0.0400 (12)	0.0333 (11)	0.0534 (14)	−0.0049 (9)	−0.0070 (11)	0.0010 (10)
N4	0.0853 (18)	0.0671 (15)	0.0643 (15)	0.0039 (13)	−0.0093 (13)	0.0222 (13)
O3	0.1035 (16)	0.0481 (12)	0.0917 (16)	−0.0091 (12)	0.0008 (13)	−0.0026 (11)
C10	0.0589 (15)	0.0417 (13)	0.0614 (15)	0.0001 (11)	0.0012 (12)	0.0083 (12)
C18	0.0427 (13)	0.0610 (16)	0.0504 (14)	−0.0058 (11)	0.0030 (10)	0.0074 (12)
C12	0.0462 (14)	0.0623 (16)	0.0511 (15)	−0.0024 (12)	−0.0008 (11)	0.0047 (12)
C4	0.0476 (14)	0.0438 (13)	0.0608 (16)	−0.0011 (11)	−0.0071 (12)	0.0096 (12)
C9	0.0475 (13)	0.0498 (14)	0.0580 (15)	−0.0037 (11)	−0.0055 (11)	0.0065 (12)
C16	0.0497 (14)	0.0527 (15)	0.0636 (16)	0.0050 (12)	−0.0069 (12)	0.0037 (12)
N1	0.0542 (14)	0.0823 (18)	0.0664 (15)	−0.0138 (13)	0.0020 (12)	0.0038 (13)
C1	0.0519 (14)	0.0554 (15)	0.0590 (16)	−0.0004 (12)	0.0113 (12)	−0.0093 (12)
C13	0.0390 (13)	0.0667 (18)	0.0671 (17)	0.0039 (12)	0.0034 (12)	0.0164 (14)
N3	0.0468 (13)	0.0648 (15)	0.126 (2)	0.0011 (12)	−0.0070 (14)	0.0286 (15)
C7	0.0475 (13)	0.0458 (14)	0.0589 (15)	0.0047 (11)	0.0045 (11)	0.0072 (11)
O1	0.0839 (16)	0.0754 (16)	0.134 (2)	−0.0189 (13)	−0.0190 (14)	−0.0140 (15)

Geometric parameters (Å, º)

S1—C2	1.743 (2)	C3—N3	1.137 (3)
S1—C1	1.816 (2)	C3—C2	1.426 (3)
S2—C5	1.750 (2)	O2—N1	1.219 (3)
S2—C6	1.820 (2)	C11—C10	1.370 (3)
N2—O3	1.215 (3)	C11—C12	1.372 (3)
N2—O4	1.222 (3)	C17—C16	1.375 (3)
N2—C11	1.468 (3)	C17—C18	1.380 (3)
C15—C14	1.382 (3)	C14—C13	1.376 (4)
C15—C16	1.388 (3)	N4—C4	1.137 (3)
C15—C1	1.504 (3)	C10—C9	1.376 (3)
C8—C7	1.384 (3)	C18—C13	1.364 (4)
C8—C9	1.388 (3)	C18—N1	1.469 (3)
C8—C6	1.501 (3)	C12—C7	1.377 (3)
C5—C2	1.351 (3)	N1—O1	1.218 (3)
C5—C4	1.431 (3)
C2—S1—C1	103.48 (12)	C16—C17—C18	118.5 (2)
C5—S2—C6	103.65 (11)	C13—C14—C15	121.3 (2)
O3—N2—O4	123.4 (2)	C5—C2—C3	119.3 (2)
O3—N2—C11	118.9 (2)	C5—C2—S1	120.32 (17)
O4—N2—C11	117.7 (2)	C3—C2—S1	120.35 (19)
C14—C15—C16	118.3 (2)	C11—C10—C9	118.4 (2)
C14—C15—C1	120.8 (2)	C13—C18—C17	121.7 (2)
C16—C15—C1	120.9 (2)	C13—C18—N1	119.0 (2)
C7—C8—C9	118.5 (2)	C17—C18—N1	119.2 (2)
C7—C8—C6	120.3 (2)	C11—C12—C7	118.2 (2)
C9—C8—C6	121.1 (2)	N4—C4—C5	177.0 (3)
C2—C5—C4	120.9 (2)	C10—C9—C8	121.0 (2)
C2—C5—S2	120.13 (17)	C17—C16—C15	121.3 (2)
C4—C5—S2	118.79 (19)	O1—N1—O2	123.4 (3)
C8—C6—S2	113.98 (17)	O1—N1—C18	118.3 (2)
N3—C3—C2	178.2 (3)	O2—N1—C18	118.3 (3)
C10—C11—C12	122.5 (2)	C15—C1—S1	115.59 (17)
C10—C11—N2	118.3 (2)	C18—C13—C14	118.9 (2)
C12—C11—N2	119.2 (2)	C12—C7—C8	121.3 (2)