Synthesis, Characterization and Optimum Reaction Conditions of Oligo-N, N -bis (2-hydroxy-1-naphthalidene) Thiosemicarbazone

Abstract

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 50–90 °C. Oligo-N, N′-bis (2-hydroxy-1-naphthalidene) thiosemicarbazone was characterized by 1H-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-1-naphthalidene) thiosemicarbazone (OHNTSC) of N, N′-bis (2-hydroxy-1-naphthalidene) thiosemicarbazone 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 1050 g mol−1 1715 g mol−1 and 1.63, using NaOCl, and 2137, 2957 g mol−1 and 1.38, using air O2 and 2155 g mol−1 4164 g mol−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) thiosemicarbazone against thermo-oxidative decomposition. The weight loss of OHNTSC was found to be 97.29% at 900 °C.