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

Isomeric 5-bromo-3-nitrosalicylaldehyde phenylhydrazone and 3-bromo-5-nitrosalicylaldehyde phenylhydrazone, C(13)H(10)BrN(3)O(3), 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.