Contrasting the supramolecular structures in the isomeric pair 5-bromo-3-nitrosalicylaldehyde phenylhydrazone and 3-bromo-5-nitrosalicylaldehyde phenylhydrazone

Abstract

Isomeric 5-bromo-3-nitrosalicylaldehyde phenylhydrazone and 3-bromo-5-nitrosalicylaldehyde phenylhydrazone, C13H10BrN3O3, both crystallize with two molecules in the asymmetric unit. In both isomers, an intramolecular O—H...N hydrogen bond links the hydroxy group and the imine N atom. In the 5-bromo-3-nitro isomer, there are two independent N—H...O hydrogen-bonded chains, each molecule in the asymmetric unit forming its own chain. These chains are then linked to form a three-dimensional framework by a combination of weak C—H...O, C—H...Br, C—H...π and π–π stacking interactions. In the 3-bromo-5-nitro isomer, N—H...O hydrogen bonds link the independent molecules alternately into a zigzag chain, which is reinforced by a weak C—H...O interaction. Individual chains are linked by a C—H...Br interaction and a three-dimensional framework is generated by π–π stacking interactions.