Thermal decomposition studies of schiff-base-substitute polyphenol-metal complexes

Abstract

The thermal behaviors of 2,3-bis[(2-hydroxyphenyl)methylene] diaminopyridine, oligo-2,3-bis[(2-hydroxyphenyl)methylene] diaminopyridine, and some oligo-2,3-bis[(2-hydroxyphenyl) methylene] diaminopyridine-metal complexes were studied in a nitrogen atmosphere with thermogravimetric analysis, derivative thermogravimetric analysis, and differential thermal analysis techniques. The decompositions of oligo-2,3-bis[(2-hydroxyphenyl) methylene] diamino pyridine-metal complexes occurred in multiple steps. The values of the activation energy (E) and reaction order of the thermal decomposition were calculated by means of several methods, including Coats-Redfern, Horowitz-Metzger, Madhusudanan-Krishnan-Ninan, van Krevelen, Wanjun-Yuwen-Hen-Cunxin, and MacCallum-Tanner on the basis of a single heating rate. The most appropriate method was determined for each decomposition step according to a leastsquares linear regression. The E values obtained by each method were in good agreement with each other. It was found that the E values of the complexes for the first decomposition stage followed the order EOHPMDAP-Ni < EOHPMDAP-Cd < EOHPMDAP-Cu < EOHPMDAP-Fe < EOHPMDAP-Zn < EOHPMDAP-Co > EOHPMDAP-Cr > EHPMDAP > EOHPMDAP.