Synthesis, characterization and optimum reaction conditions of oligo-N, N′-bis (2-hydroxy-1-naphthalidene) thiosemicarbazone

The oxidative polycondenzation reaction conditions of N, N'-bis (2-hydroxy- 1-naphthalidene) thiosemicarbazone (HNTSC) using air oxygen, H2O2 and NaOCl were studied in an aqueous alkaline medium between 50-90degreesC. Oligo-N, N'-bis (2-hydroxy- 1 -naphthalidene) thiosemicarbazone was characterized by H-1-NMR, FT-IR, UV-Vis, size exclusion chromatography (SEC) and elemental analysis techniques. Solubility testing of oligomer was investigated using organic solvents such as DMF, THF, DMSO, methanol, ethanol, CHCl3, CCl4, toluene acetonitrile, ethyl acetate, concentrated H2SO4 and an aqueous alkaline solution. Using NaOCl, H2O2 and air O2 oxidants, conversion to oligo-N, N'-bis (2-hydroxy-lnaphthalidene) thiosemicarbazone (OHNTSC) of N, N'-bis (2-hydroxy- 1 -naphthalidene) thiosernicarbazone was found to be 85, 80 and 76%, respectively, in an aqueous alkaline medium. According to the SEC analyses, the number-average molecular weight, weight-average molecular weight and polydispersity index values of OHNTSC synthesized were found to be 1050gmol(-1) 1715 gmol(-1) and 1.63, using NaOCl, and 2137, 2957 gmol(-1) and 1.38, using air O-2 and 2155 gmol(-1) 4164 gmol(-1) and 1.93, using air H2O2, respectively. Also, TG analysis was shown to be unstable of oligo-N, N'-bis (2-hydroxy-1-naphthalidene) thiosernicarbazone against thermo-oxidative decomposition. The weight loss of OHNTSC was found to be 97.29% at 900 degreesC.