On-line version ISSN 0717-9707
J. Chil. Chem. Soc. vol.55 no.1 Concepción 2010
J. Chil. Chem. Soc, 55, N° 1 (2010), pág: 8-10
CRYSTAL STRUCTURE STUDY OF 1-(2-FURYL)-3-(3-METHYL-2-THIENYL)-PROPENONE,C12H10O2S
Y. MORENO1*, F. BROVELLI2, M. DAHROUCH3, R. BAGGIO4, L. MORENO5
1 Depto. de Química Analítica e Inorgánica, Fac. Cs. Químicas, Universidad de Concepción, Chile
2 Depto. de Ciencias Básicas, Campus Los Angeles, Universidad de Concepción, Chile
3 Depto. de Química Orgánica, Fac. Cs. Químicas, Universidad de Concepción, Chile
4 Departamento de Física, Comisión Nacional de Energía Atómica, Buenos Aires, Argentina.
5 Departamento de Ciencias, Universidad del Bio Bio, Casilla 447, Chillan, Chile.
This structure is related to synthesis of new polythiophene derivatives. Their most interesting aspects are to be found in their interatomic interactions, of varied type (C—H … O, C—H … π, π … π) and strength. In the title compound C12H10O2S there are two independent molecules per asymmetric unit but unlike the former one (where interatomic interactions do not "mix" them), herein both types of independent molecules are interlinked through H-bonding interactions to form broad strips along , four molecules in width and displaying a zig-zag pattern. These structures fit into each other along the  direction, in a "gear-like" fashion, giving raise to some π — π contacts.
The polythiophene family of compounds has undergone a important progress in the last few years due to their technological applications in different areas as photochemistry and electrochemistry.1-3
It is possible to synthesize conjugated polymers as organic wide-gap semi-conductors, with electronic and optoelectronic applications. In this field, polythiophenes derivatives are among those more studied for their use in organic light-emitting diodes.4-6
In general there is not much structural information available for these families. Theoretical studies show that the conformations of these molecules are the result of the interactions between the electronic coupling of the oxygen in the carbonyl group and the heteroatom in the neighboring ring, indicating a favored conformation.7-9
On the other hand, these compounds can act as ligands in order to coordínate metal ions and give origin to poly-dimensional structures, due to the particular disposition of their donor atoms, O and S.
The precursors employed have been a series of heterocyclic α,ß'-unsaturated ketones containing thiophene and/or furane rings (1,2,5) similar to the molecule reported in this work; these molecules have been studied and characterized by electrochemical and ab-initio methods.10-16
Herein we present a structural study of 1-(2-furyl)-3-(3-methyl-2-thienyl)-propenone, C12H10O2S, see scheme (1). This is the second example of a family that we have synthesized, the recently published (1,5-bis(3-methyl-2-thienyl) penta-1,4-dien-3-one, C15H14OS2)17 being he first one, and both structures present analogous intermolecular interactions. In fact, other research groups have studied similar compounds, which have in general very similar structural characteristics.18
Compound C12H10O2S was obtained following the procedure described by Brovelli et al.19
3-methyl-2-thiophenecarboxaldehyde (0,1 mol) was dissolved in acetylfuran (0, lmol). The mixture was cooled to 0°C and KOH/ethanol 20% was slowly added. The mixture was stirred for 10 h, and it was filtered and washed with cool ethanol. Pale yellow crystals were obtained from an ethanol/ water solution (5:1). The yield was 69%. Elemental Analysis (%) (exp/theo): 64.65/64.69 (C); 3.70/3.95 (H);15.43/15.67 (O); 16.22/15.70 (S).
The IR spectrum was carried out in an FTIR-NICOLET MAGNA 550.
Hydrogen atoms were placed at calculated positions (C-H: 0.93-0.97 A) and allowedto ride; methyl groups were allowedto rotate as well. Displacement factors were taken as U(H)isot = x.U(host), x: 1.2-1.5. The Table 1 shows some crystal data.
Datacollection: SMART-NT20; cell refinement: SAINT-NT20; datareduction: SAINT-NT; program(s) used to solve structure: SHELXS9721; program(s) used to refine structure: SHELXL9711; molecular graphics: SHELXTL-NT12; software used to prepare material for publication: SHELXTL-NT, PLATON.13
RESULT AND DISCUSSION
Fig. 1 shows an ellipsoid plot of the two independent molecules in C12H10O2S; both have the same conformation and consist of two terminal rings (thiophene and furane) bridged by a propenone link, which leaves both rings almost coplanar to the whole group and with their substituent atoms in cis orientation to each other. The carbonyl oxygen is in turn, trans to both heteroatoms. One of this independent propenone groups presents some disorder, accounted for in refinement by some enlarged displacement ellipsoids (see refinement section).
The IR spectrum agrees with the X-ray structure. It shows the bands typical for the functional groups, but as the molecule is almost planar (there is a small torsión angle between aromatic rings), the conjugation of C=O with C=C bond result in delocalization of % electrons in both unsaturated groups; this causes absorption at lower wave-numbers; then C=O, ~1650cm-1 ; C=C, ~1600cm-1 .
The planarity of the group is perturbed by a slight twist along the bridge axis. The rotation between rings (10.4(1), 17.8(2) is larger in the disordered moiety as are the differences between equivalent bonds, probably an artifact of refinement.
Other interesting aspects are to be found in the hydrogen atoms and their interatomic interactions of varied type (C—H … O, C—H … π, π — π) and strength.
The two independent molecules per asymmetric unit, are interlinked through some C—H … O interactions having the carbonyl oxygen as acceptor (structural data are given in Table 1) to form broad strips along , four molecules in width (Fig. 2a) and displaying a lateral zig-zag pattern (Fig. 2b). These structures fit into each other along  and  directions, in a "gear-like" fashion, and are further connected through C—H … O, C—H … π, π — π contacts described in Tables 2 and 3 respectively. Some important distances (Å) and angles (°) are given in Table 4. More information like coordinated and thermal factors of agitation can be found in the Cambridge Database (see annexed materials)
Symmetry codes: (v) 3/2 — x, 1/2 — y,1 — z; (vi) 1 — x,-y, 1 — z For the group codes, see Fig 1. ce (center-to-center distance): distance between ring centroids; da: (dihedral angle) angle between planar groups; ipd (interplanar distance): mean distance from one plañe to the neighbouring centroid. (For details, see Janiak 200025)
Crystals of C12H10O2S, were very small and weakly diffracting, providing rather poor data sets. This was confirmed by the structure solution and the refinement of the models: atoms C5' and C6' in the central bridge of one of the two independent moieties appeared severely disordered, and the attempts to model this part with split wouldn't retine properly. A metrically constrained refinement of an un-split model was thus performed, which converged smoothly at the cost of accepting large anisotropic displacement ellipsoids, elongated along the normal to the planar bridge in order to account for the disordered electrón density in the region . This problematic zone has been represented in Fig. 1 by hollow bonds.
Hydrogen atoms were placed at calculated positions (C-H: 0.93-0.97 Å) and allowed to ride; methyl groups were allowed to rotate as well. Displacement factors were taken as U(H)isot = x.U(host), x: 1.2-1.5
We acknowledge funding by project DIUC 208.021.026-1.0 and 209.021.028-1.0. CIPA Chile. Dr. Thierry Roisnel of Centre de Diffractométrie X of Université de Rennes 1 "Sciences Chimiques de Rennes" by diffraction experiences.
We also acknowledge the Spanish Research Council (CSIC) for providing us with a free-of-charge license to the CSD system (Alien, 200226).
The crystal structure has been deposited atthe Cambridge Crystallographic Data Centre and allocated the deposition number: CCDC 759088
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(Received: August 27, 2009 - Accepted: January 5, 2010)