Crystal structure and synthesis of 3-(1H-pyrrol-2-yl)-1-(thiophen-2-yl)propanone

The molecule is essentially planar with a maximum deviation of 0.085 Å from the mean plane through all non-H atoms. In the crystal, N—H⋯O hydrogen bonds involving the pyrrole amine and the ketone carbonyl O atoms link the molecules into [100] ribbons which form offset stacks along the b axis.


Structural commentary
The title compound 1 crystallizes in a polar non-centrosymmetric space group (Pna2 1 ) and is almost planar in its crystalline form ( Fig. 1; Table 1) with deviations ranging from À0.059 (3) (C11) to 0.085 Å (C7) from the mean plane of all non-hydrogen atoms. The pyrrole ring (N1/C8-C11) is rotated out of the plane through the ketone and thiophenyl groups (S1/O1/C1-C7) by 4.32 (10) . The aliphatic chain linking the two ring systems has a trans conformation and the nitrogen atom (N1) of the pyrrole ring is protonated. Atom N1 is oriented opposite to the sulfur atom S1 of the thiophene ring to enable intermolecular hydrogen bonding (Fig. 2). Atom S1 lies on the same side of the molecular backbone as the oxygen of the ketone (O1).

Supramolecular features
Hydrogen bonding dominates the crystal packing of 1 and occurs between the amine group and the carbonyl oxygen ( Fig. 2, Table 1), linking the molecules into a head-to-head ribbon-type assembly that extends down the a axis in an alternating X-pattern (Fig. 3). The angle between the alternating molecules in this X-pattern is 88.804 (8) . The ribbons form offset stacks along the b axis with centroid-centroid distances of 3.9257 (15) Å between the centroids of adjacent pyrrole or thiophene rings and a plane shift distance of 1.89 (3) Å between any two molecules in the three-dimensional crystal structure. C-HÁ Á ÁO interactions also occur.

Figure 2
The hydrogen bonding (dashed line) between the amine group and the carbonyl oxygen atom (Table 1). Displacement ellipsoids are drawn at the 50% probability level.

Figure 3
View of the X-pattern in the packing, viewed approximately along the a axis. Displacement ellipsoids are drawn at the 50% probability level.

Figure 1
The molecular structure of the title compound, showing the atom labelling. Displacement ellipsoids are drawn at the 50% probability level.
0.233 Å (S1); the deviations in LINFET B are smaller ranging from À0.032 Å for C22 to 0.055 Å for O2. They both exhibit the same trans conformation seen in the title molecule. Nonclassical hydrogen bonding exists between a C-H group and the carbonyl oxygen, O1 with a C-HÁ Á ÁO distance of 3.326 (6) Å . This bonding network results in three separate sheets, parallel to the a-axis. A second non-classical hydrogenbonding network [C-HÁ Á ÁO = 2.381 (4) Å ] is observed extending along the c-axis direction, generating a staggered ribbon. The combination of these two networks gives rise to a three-dimensional structure. Ískeleli et al., 2005) comprises two furan heterocycles linked by an ,-unsaturated ketone aliphatic chain. There are also two independent molecules in the asymmetric unit (SANRIJ A and SANRIJ B), both of which are less planar than 1, LINFET A and LINFET B. The largest deviation from the molecular plane is for C17 (0.157 Å ) in SANRIJ A and C18 (À0.152 Å ) in SANRIJ B. Again, a non-classical hydrogen bonding network exists [C-HÁ Á ÁO = 2.473 (18) Å ] between aryl C-H atoms and the carbonyl oxygen. Each molecule participates in two hydrogen bonds and the network extends in a linear fashion along the b-axis direction, forming a network structure.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. H atoms were placed in their expected calculated positions and refined as riding: C-H = 0.95-0.98 Å with U iso (H) = 1.2 U eq (C).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.