Crystallographic and conformational analysis of two novel trans-azo benzene compounds

• Published in: Structural chemistry 2009-10, Vol.20 (5), p.903-910
• Main Authors: Karabıyık, Hasan, Petek, Hande, İskeleli, Nazan Ocak, Albayrak, Çiğdem
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Computer Applications in Chemistry; Original Research; Physical Chemistry; Theoretical and Computational Chemistry
• ISSN: 1040-0400; 1572-9001
• DOI: 10.1007/s11224-009-9490-4

The molecular and crystal structure of ( E )-2-Acetyl-4-(2-bromophenyldiazenyl)phenol ( 1 ) and ( E )-2-Methyl-4-( o -tolyldiazenyl)phenol ( 2 ) were characterized and determined by single crystal X-ray diffraction method besides spectroscopic means. The periodic organization of 1 is stabilized by C–H···O type weak H-bond and Br···O type weak halogen bonding and thus, a two dimensional puckered network is established almost parallel to ( ) the plane. Molecules of 2 are linked into C (7) chains generated by translation along the [1 0 1] direction with the aid of O–H···N type H-bonds, and these chains are strengthened by C–H···π interactions involving o -tolylphenol ring. Quantum chemical studies at B3LYP/6-311 ++G(d,p) level reveal that potential barrier of the compounds around Ar–N torsions is of double minimum character unless it is defected by the presence of o -substituent groups in the vicinity of the azo bridge. The results from crystallographic and quantum chemical studies suggest that azo benzene compounds may adapt non-planar geometry apart from the most stable planar conformation, which is located on the secondary minima of double potential barrier regarding rotational motion around Ar–N bonds.