3-(Pyridin-2-yl)coumarin

In the title compound, C14H9NO2, the dihedral angle between the pyridine ring and the lactone ring is 10.40 (3)°. The coumarin ring system is nearly planar, with a dihedral angle of 1.40 (2)° between the lactone and benzene rings. An intramolecular C—H⋯O hydrogen bond occurs. In the crystal, inversion dimers linked by pairs of C—H⋯O interactions occur, generating R 2 2(14) loops.

In the title compound, C 14 H 9 NO 2 , the dihedral angle between the pyridine ring and the lactone ring is 10.40 (3) . The coumarin ring system is nearly planar, with a dihedral angle of 1.40 (2) between the lactone and benzene rings. An intramolecular C-HÁ Á ÁO hydrogen bond occurs. In the crystal, inversion dimers linked by pairs of C-HÁ Á ÁO interactions occur, generating R 2 2 (14) loops.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
Coumarins are an important class of organic compounds, which have been extensively investigated due to their applications in biological, chemical and physical fields (Walshe, et al., 1997;Fylaktakidou, et al., 2004;Yu, et al., 2010;Trenor, et al., 2004). The photophysical and spectroscopic properties of the coumarin derivatives can be readily modified by the introduction of substituents in parent coumarin, converting themselves into more useful products and more flexibility to fit well in various applications (Griffiths, et al., 1995;Yu, et al., 2006). Among the substituted coumarins, heterocyclic groups at the 3-position have given rise to many derivatives of biological and structural importance. For example, 3-pyridyl substituted coumarins are not only known for their diverse physiological activities (Moffett, et al., 1964), but also have outstanding optical properties including high quantum yields and superior photostability (Yu, et al., 2010). In addition, 3-pyridyl substituted coumarins have attracted considerable interest due to their use as ligands for Ir (III) complexes which possess higher quantum yields and much higher brightnesses (Ren, et al., 2008;Ren, et al., 2010). In this paper, we report the synthesis and crystal structure of 3-(pyridin-2-yl)coumarin.
The molecular structure of the title compound and the ORTEP structure is shown in Fig.1. The bond lengths and angles in the molecule are within normal ranges (Allen et al., 1987). Both the pyrone and benzene rings in the coumarin motif are essentially planar. The dihedral angle between them is 1.40 (2)°, thus the coumarin moiety is essentially planar. The pyridine ring makes an angle of 10.40 (3)° with the pyrone ring, they are not coplanar.

Experimental
Salicylaldehyde (0.1 mol) and pyridine-2-acetonitrile (0.1 mol) were dissolved in 30 ml of anhydrous alcohol, and then piperidine (0.1 ml) was added stepwise under ice bath. The mixture was stirred for 12 h at room temperature, then treated with HCl (50 ml, 3.5%) and refluxed for 10 h to hydrolyze the iminocoumarin. When the reaction was finished, the acidic solution was neutralized with aqueous ammonia until the pH was 7. Colourless blocks of (I) were obtained by slow evaporation of the methanol solution at room temperature.

Refinement
Non-H atoms were refined anisotropically. H atoms were treated as riding atoms with distances C-H = 0.93 Å (ArH). The isotropic displacement parameters for all H atoms were set equal to 1.2 U eq of the carrier atom.
Figures Fig. 1. The molecular structure of (I) with displacement ellipsoids for the non-hydrogen atomes drawn at the 30% probability level.