(E)-5-(2-Thienylmethyleneamino)quinolin-8-ol

Two molecules of the title compound, C14H10N2OS, are hydrogen bonded about a center of inversion. In the molecule, the two aromatic rings are twisted by 37.27 (5)° with respect to one another. The azomethine bond is in the E configuration.

Two molecules of the title compound, C 14 H 10 N 2 OS, are hydrogen bonded about a center of inversion. In the molecule, the two aromatic rings are twisted by 37.27 (5) with respect to one another. The azomethine bond is in the E configuration.

Related literature
For information about the utility of azomethines, see: Dufresne et al. (2006); . For related structures, see: Chen et al. (1999). For an analog with an aryl ring in place of the thienyl ring, see Manecke et al. (1972).
(E)-5-(2-Thienylmethyleneamino)quinolin-8-ol S. Dufresne, A. N. Bourque and W. G. Skene Comment Compound (I) was prepared as a new ligand for metal-ligand charge transfer complexes. The structure of (I) consists of quinolin-2-ol covalently linked to a thiophene unit by an azomethine bond with more stable E isomer being observed. The crystal structure has a P21/c symmetry as seen in figure 2. No solvent molecules or counter-ions were found in the crystal structure.
The mean planes of the two aryl moieties are twisted by 37.27 (5)° from the azomethine bond to which they are connected.
This angle is smaller, i.e. 65°, (Manecke et al., 1972) than its homoaryl analogue. Steric hindrance between H6 and H10 is responsible for the twist between the mean planes similar to a thiophene azomethine, whose aryl mean planes are twisted by 33° Skene et al., 2006).
Hydrogen bonding takes place between two quinolin-8-ol moieties to form a supramolecular dimer. Figure 2 shows the two symmetry related hydrogen bonds between O1-H1···N1î^ and O1î^-H1î^···N1 that form the dimer. The length and the angle of this bond are 2.927 (2) Å and 136°, respectively. The two quinolin-2-ol involved in the hydrogen bonding are shifted by 0.593 Å.

Experimental
The title compound was synthesized by means of an acid catalyzed condensation of 5-amino-8-hydroxyquinoline with 2-thiophenecarboxaldehyde in ethanol with catalytic trifluoroacetic acid. The reaction was held at reflux for 20 h with stirring, cooled to room temperature and the volume reduced. Ice-cold distilled water was added to this solution causing a yellow solid to precipitate. The yellow solid was collected, washed with water and then dried under reduced pressure overnight. Crystals were obtained by slow evaporation of a concentrated solution of (1) in acetone.  Fig. 1. ORTEP representation of (I) with the numbering scheme adopted (Farrugia 1997). Ellipsoids drawn at 30% probability level.  as large as those based on F, and R-factors based on ALL data will be even larger.