Structural and computational studies of azo dyes in the hydrazone form having the same pyridine-2,6-dione component (II): C.I. Disperse Yellow 119 and C.I. Disperse Yellow 211

The molecular and crystal structures of two yellow, azo disperse dyes having the same pyridine-1-ethyl-3-cyano-4-methyl-2,6-dione backbone, namely C.I. Disperse Yellow 119 and C.I. Disperse Yellow 211 were studied. Both dyes crystallize in the hydrazone form both at 291 and 120 K, with hydrogen bonding and π–π stacking interactions playing important roles in determining the packing frameworks; mean interlayer separations of 3.002(3) and 3.316(6) Å, respectively, were obtained. Theoretical calculations were undertaken to compare the energy differences between the single-crystal and the energy-minimized structures of the compounds as well as those between the pyridine-2,6-dione and the 2-hydroxy-6-pyridone isomers.