Diethyl 2,5-bis­[(1E)-(1H-pyrrol-2-yl­methyl­idene)amino]­thio­phene-3,4-dicarboxyl­ate

Stéphane Dufresne; W G Skene

doi:10.1107/S1600536811031576

. 2011 Aug 11;67(Pt 9):o2302. doi: 10.1107/S1600536811031576

Diethyl 2,5-bis[(1E)-(1H-pyrrol-2-ylmethylidene)amino]thiophene-3,4-dicarboxylate

Stéphane Dufresne ^a, W G Skene ^a,^*

PMCID: PMC3200839 PMID: 22058937

Abstract

In the crystal structure of the title compound, C₂₀H₂₀N₄O₄S, the azomethine group adopt E conformations. The pyrrole units are twisted by 10.31 (4) and 18.90 (5)° with respect to the central thiophene ring. The three-dimensional network is close packed and involves N—H⋯O, N—H⋯N, C—H⋯N and C—H⋯O hydrogen bonding.

Related literature

For general background, see: Dufresne et al. (2007 ▶, 2011 ▶). For thiophene azomethines, see: Dufresne et al. (2006 ▶, 2010a ▶,b ▶). For alkene comparison, see: Ruban et al. (1975 ▶); Zobel et al. (1978 ▶).

Experimental

Crystal data

C₂₀H₂₀N₄O₄S
M _r = 412.46
Orthorhombic,
a = 16.898 (3) Å
b = 12.643 (3) Å
c = 9.4220 (19) Å
V = 2012.9 (7) Å³
Z = 4
Cu Kα radiation
μ = 1.73 mm⁻¹
T = 150 K
0.10 × 0.03 × 0.03 mm

Data collection

Bruker SMART 6000 diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.841, T _max = 0.947
17313 measured reflections
3040 independent reflections
3004 reflections with I > 2σ(I)
R _int = 0.028

Refinement

R[F ² > 2σ(F ²)] = 0.024
wR(F ²) = 0.064
S = 1.04
3040 reflections
264 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.19 e Å⁻³
Δρ_min = −0.15 e Å⁻³
Absolute structure: Flack (1983) ▶, 1275 Friedel pairs
Flack parameter: 0.085 (12)

Data collection: SMART (Bruker, 2003 ▶); cell refinement: SAINT (Bruker, 2004 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶) and ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: UdMX (Marris, 2004 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811031576/zq2118sup1.cif

e-67-o2302-sup1.cif^{(20.9KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811031576/zq2118Isup2.hkl

e-67-o2302-Isup2.hkl^{(149.2KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811031576/zq2118Isup3.cml

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H100⋯O3ⁱ	0.88	2.37	3.040 (2)	133
N4—H400⋯O1ⁱⁱ	0.88	2.47	3.174 (2)	138
N4—H400⋯N2ⁱⁱ	0.88	2.59	3.2136 (19)	128
C3—H3⋯N4ⁱⁱⁱ	0.95	2.56	3.441 (2)	155
C13—H13⋯O3^iv	0.95	2.51	3.126 (2)	123

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) .

Acknowledgments

The authors acknowledge financial support from the Natural Sciences and Engineering Research Council Canada, the Centre for Self-Assembled Chemical Structures, and the Canada Foundation for Innovation. SD thanks both NSERC and the Université de Montréal for graduate scholarships.

supplementary crystallographic information

Comment

During our on-going research relating to conjugated azomethines (Dufresne et al., 2007; Dufresne & Skene, 2010a,b; Dufresne & Skene, 2011) we prepared the title compound (I), C₂₀H₂₀N₄O₄S. To the best of our knowledge, there are very few reported crystal structures of azomethines consisting of pyrrole and thiophene units together. The molecular structure was confirmed by a X-ray diffraction study (Fig. 1). Neither solvent molecules nor counter-ions were found in the closed-packing of the crystal structure.

A major point of interest is the azomethine bond which adopts the E configuration. The bond lengths for C4—C5, N2—C5 and N2—C6 are 1.429 (3), 1.294 (3) and 1.379 (2) Å, respectively. The related bonds C10—C11, N3—C10 and N3—C9 are 1.434 (3), 1.288 (3) and 1.379 (3) Å, respectively. All bond distances are consistent with those of a similar conjugated compound consisting uniquely of thiophenes with two azomethine bonds (Dufresne et al., 2006). The analogues bond lengths for the all-thiophene counterpart are: 1.441 (4), 1.272 (3) and 1.388 (3) Å. It was found that the three heterocycles of (I) are not perfectly coplanar. This was confirmed by measuring the dihedral angles between the planes described by both terminal pyrroles and the plane described by the central thiophene. The dihedral angle between the N1-pyrrole and thiophene planes is 10.31 (4)°, while that for the thiophene and N4-pyrrole planes is 18.90 (5)°. The measured angles are similar to the all-thiophene analogue whose terminal thiophenes are twisted by 9.04 (4)° and 25.07 (6)° with the central thiophene. The pyrrole N-H is involved in several N—H···O and N—H···N donor-acceptor interactions while C—H···N and C—H···O are also observed (Table 1). All these interactions are responsible for the overall extended three-dimensional crystal network (Fig. 2), while no π-stacking was found.

Experimental

In anhydrous toluene (25 mL) was added 1H-pyrrole-2-carbaldehyde to which was subsequently added DABCO, TiCl₄ in toluene at 0 °C and then diethyl 2,5-diaminothiophene-3,4-dicarboxylate was added. The mixture was then refluxed for 30 minutes and the solvent, after which the solvent was removed. Purification by flash chromatography yielded the title product as a red solid. Single crystals were obtained by slow evaporation of an acetone solution of the title compound.