Condensed heteroaromatic systems including a thiophene ring.

The thermal stabilities of 2-mercapto-3-formylbenzob]thiophene and its chelates with Cu(II) and Co(II), of 2-mercapto-3-iminomethylbenzob]thiophene and its chelates with Cu(II), Co(II), Ni(II), and Zn(II), and of N,N′-bis(2-mercaptobenzo b]-3-thenylidene)ethylenediamine and its chelates with Cu(II), Co(II), and Ni(II) were investigated by differential-thermal and thermogravimetric analysis. The temperature of the onset of decomposition and the character of the decomposirion of the ligands and chelates were established. It was found that the investigated chelates can be arranged in the following order with respect to increasing thermal stability: Cu < Co < Zn < Ni. The most thermally stable ligand is N,N-bis (2-mercaptobenzob]-3-thenylidene)ethylenediamine. The effectiveness of the ligands and chelates as stabilizers for polycaproamide fibers were compared. It was found that of the investigated compounds, the copper chelates are effective stabilizers. In a study of the thermal behavior of the copper chelates in an inert gas atmosphere it was established that the character of the thermal decomposition of the most effective of them — {it(N,N′-bis)2-mercaptobenzob]-3-thenylidene)-ethylenediaminato} Cu(II) — is identical both in the presence of air oxygen and in a nitrogen atmosphere, i.e., the chelate does not undergo oxidation at temperatures up to 270?C.