Synthesis, characterization, conductivity and thermal degradation of oligo-2-[(4-morpholin-4-yl-phenyl)imino]methylphenol and its oligomer–metal complex compounds

Abstract

Schiff base oligomer of 2-[(4-morpholin-4-yl-phenyl)imino]methylphenol (2-MPIMP) was synthesized via oxidative polycondensation reaction by using air O 2 and NaOCl oxidants in an alkaline medium between 40 and 90 °C. The structure of oligo-2-[(4-morpholin-4-yl-phenyl)imino]methylphenol (O-2-MPIMP) was characterized by using 1H, 13C NMR, FT-IR, UV–vis, size exclusion chromatography (SEC) and elemental analysis techniques. At the optimum reaction conditions, the yield of O-2-MPIMP was found to be 73% (for air O 2 oxidant) and 97% (for NaOCl oxidant). According to the SEC measurements, the number-average molecular weight ( M n), weight-average molecular weight ( M w) and polydispersity index (PDI) values of O-2-MPIMP was found to be 1725, 2030 mol −1 and 1.177, respectively, using air O 2 and 1345, 1490 g mol −1 and 1.108, using NaOCl, respectively. Oligomer–metal complex compounds were synthesized from the reactions of O-2-MPIMP with Cu 2+, Co 2+, Cd 2+, Zn 2+, Pb 2+ and Zr 4+ ions. Electrochemical the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and electrochemical energy gaps ( E ′ g ) for 2-MPIMP and O-2-MPIMP were found to be between −5.85 and −5.82, −2.63 and −2.87, 3.22 and 2.95 eV. Also, conductivity values of oligomer and oligomer–metal complex compounds were determined from their solid conductivity measurements. Conductivity measurements of doped and undoped Schiff base oligomer and its metal complexes were carried out by electrometer at room temperature and atmospheric pressure and were calculated from four-point probe technique. When iodine was used as doping agent, conductivity of this oligomer and its metal complexes were observed to be increased.