2-Phenyl-1,3-selenazole-4-carboxylic acid

In the title compound, C10H7NO2Se, the two rings are twisted, making a dihedral angle of 12.42 (9)°. In the crystal, pairs of molecules are disposed about an inversion center, generating O—H⋯O hydrogen-bonded dimers.

In the title compound, C 10 H 7 NO 2 Se, the two rings are twisted, making a dihedral angle of 12.42 (9) . In the crystal, pairs of molecules are disposed about an inversion center, generating O-HÁ Á ÁO hydrogen-bonded dimers.

Comment
It has well been confirmed that the derivatives of selenazole are important in multiple fields such as chemistry and biochemistry owing to their biological activities (Srivastava et al., 1983;Boritzki et al.,1985). Interested in this field, we have been engaged in a major effort directed toward the development of syntheses of new selenazole carboxylic acid and their transition metal complexes. In a few of articles we have reported our partial research results (Zhao et al., 2010;Shen et al., 2011). Herein,we crystallize the organic ligand 2-phenyl-4-selenazole carboxylic acid.
The structure of the title, (C 10 H 7 NO 2 Se),suitable for X-ray, was obtained by chance. The structure of the complex is shown in Fig.1, which reveals that all atoms in each molecule are nearly coplanar in the centrosymmetric unit. The molecule is essentially planar with the dihedral angle between two neighboring rings are 12.415 (89)°. In the molecule of 2-phenyl-4selenazole carboxylic acid,the Se-C bond length range from 1.832 (2) Å-1.891 (2)Å and the angle C-Se-C is 84.78 (10)°.
The molecules arranged in the crystal at regular intervals with O-H···O hydrogen bonds. The end to end hydrogenbonding interactions lead to the formation a one-dimensional structure framework along the b axis, Fig 2. Between adjacent triple-helix chains there exist weak π···π interactions.

Experimental
Reagents and solvents used were of commercially available quality and without purified before using. K 2 Cr 2 O 7 (0.588 g, 2 mmol) was added to a mixed solution of acetic acid (50 ml) with 2-phenyl-4-selenazole carbinol (0.248 g, 1 mmol) under stirred conditions at room temperature. Few minutes later lots of red deposit appeared. After the deposit was filtered out, a light red solution was kept for evaporating. Some red single crystals were obtained about 19 days later.

Refinement
The structure was solved by direct methods and successive Fourier difference synthesis. The H atoms bonded to C atoms were positioned geometrically and refined using a riding model [aromatic C-H = 0.93 Å (U iso (H) = 1.2U eq (C))]. The H atoms bonded to O atoms were located in difference Fourier maps and refined with O-H distance restraints of 0.85 (2) and U iso (H) = 1.5U eq (O). Fig. 1 Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.