Crystal structures of four 1-(aryl)-[1,2,4]triazolo[4,3-a]quinoxaline derivatives

Abstract

The crystal structures of four 1-aryl-[1,2,4]triazolo[4,3-a]quinoxaline derivatives, 2, are reported: [aryl = 3-ClC6H4: 2a; 2-HOC6H4:2b;2,3-(HO)2C6H3: 2c; and 3,4-(MeO)2C6H3: 2d] The compounds, 2, were prepared by oxidation of substituted arenealdehyde quinoxalin-2-ylhydrazones, 1, using ferric chloride in alcohol. In each of the four compounds, the three ring -[1,2,4]triazolo[4,3-a]quinoxaline moiety is a near planar moiety, with all ring atoms within 0.1 Å of the best plane. There are large dihedral angles, 59 ± 7°, between the [1,2,4]triazolo[4,3-a]quinoxaline system and the phenyl ring. The ortho sited hydroxyl groups in 2c are jointly involved in a single OH⋯O intramolecular hydrogen bond and individually in OH⋯N intermolecular interactions, while the hydroxyl group in 2b is involved in an intermolecular OH⋯N hydrogen bond. These and weaker intermolecular interactions, including some of CH···Z (Z = O, N and or π) and π···π interactions generate the supramolecular arrangements in 2b and 2c. Intermolecular CH···Z (Z = O, N and or π) and π···π interactions are only present in 2a and 2d.