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 H2O2 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·H2O and H2O2 in the presence of NH3·H2O 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 H2O2 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 H2O2 oxidation, metal-ion complexation and subsequent demetallization by Na2S.