Synthesis, Characterization and Anti-microbial Activity of Oligo-N-2-aminopyridinylsalicylaldimine and Some Oligomer-metal Complexes

Abstract

The oxidative polycondensation and optimum reaction conditions of N-2-aminopyridinylsalicylaldimine using air oxygen, H2O2 and NaOCl were determined in an aqueous alkaline solution between 40–90 °C. Oligo-N-2-aminopyridinylsalicylaldimine (OAPSA) was characterized by using 1H-NMR, FT-IR, UV-vis and elemental analysis. N-2-aminopyridinylsalicylaldimine was converted to oligomer by oxidizing in an aqueous alkaline medium. The number average molecular weight (M n), weight average molecular weight (M w) and polydispersity index (PDI) values were found to be 7487 g mol−1, 7901 g mol−1 and 1.06, respectively. According to these values, 70% of N-2-aminopyridinylsalicylaldimine turned into oligo-N-2-aminopyridinylsalicylaldimine. During the polycondensation reaction, a part of the azomethine (–CH=N–) groups oxidized to carboxylic (–COOH) group. Besides, the structure and properties of oligomer-metal complexes of oligo-N-2-aminopyridinyl salicylaldimine (OAPSA) with Cu (II), Ni (II), and Co (II) were studied by FT-IR, UV-vis DTA, TG and elemental analysis. Anti-microbial activities of the oligomer and its oligomer-metal complexes have been tested against C. albicans, L. monocytogenes, B. megaterium, E. coli, M. smegmatis, E. aeroginesa, P. fluorescen and B. jeoreseens. Also, according to the TG and DTA analyses, oligo-N-2-aminopyridinylsalicylaldimine and its oligomer-metal complexes were found to be stable thermo-oxidative decomposition. The weight loss of OAPSA found to be 20%, 50% and 98% at 350 °C, 535 °C and 1000 °C, respectively.