In situ metal-ion complexation and H2O2 oxidation for a pyridine-2,6-dione based disperse yellow dye

Abstract We reported herein the studies on in situ metal-ion complexation and H 2 O 2 oxidation for a pyridine-2,6-dione based heterocyclic dye (C.I. Disperse Yellow 211) in the hydrazone-tautomeric form. Our results reveal that four kinds of compounds can be isolated successfully by treating this dye with Cu(OAc) 2 ·H 2 O and H 2 O 2 in the presence of NH 3 ·H 2 O and DMF, namely oxidation and complexation product 1 , oxidation product 2 , ring-degradation (ring-opening and oxidative cleavage) product 3 and complexation product 4 . In contrast, when copper(II) and nickel(II) ions were used under the similar reaction condition just in the absence of H 2 O 2 oxidant, only direct complexation products 4 and 5 could be obtained. It is noted that organic compounds 2 and 3 adopt the same hydrazone-tautomeric form as that in C.I. Disperse Yellow 211, but all three dye-metal complexes 1 and 4 – 5 exhibit the deprotonated azo form. A possible reaction mechanism is proposed for the formation of hydroxyl-addition and ring-degradation products 1 – 3 . Furthermore, we have provided an effective preparation method for new dyes with an additional ortho phenolic hydroxyl group by H 2 O 2 oxidation, metal-ion complexation and subsequent demetallization by Na 2 S.