Thermal stability, conductivity, and band gaps of oligo-2-[(phenylimino) methyl] phenol and oligomer-metal complexes

Schiff base oligomer of 2-[(phenylimino) methyl] phenol (2-PIMP) was synthesized via oxidative polycondensation reaction in an alkaline medium by using air (O2) as oxidant. Oligomer-metal complex compounds were synthesized from the reactions of oligo-2-[(phenylimino) methyl] phenol (0-2-PIMP) with Co+2, Ni+2, Cu+2, Cr +3, Pb+2, and Zn+2 ions. While synthesized Schiff base oligomer was soluble in most common organic solvents, its metal complexes were only soluble in dimethylsulphoxide. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and electrochemical energy gaps (E'g) of monomer, oligomer, and oligomer-metal complexes were calculated from oxidation and reduction onset values. Also, optical band gaps (Eg) of monomer, oligomer, and oligomer-metal complexes were calculated from their absorption edges. Conductivity measurements of doped and undoped Schiff base oligomer and oligomer-metal complexes were carried out by electrometer at the room temperature and atmospheric pressure and were calculated by four-point probe technique. When iodine was used as doping agent, conductivity of oligomer and oligomer-metal complexes were observed to be increased. The weight losses of 2-PIMP, 0-2-PIMP, 0-2-PIMP-Co, O-2-PIMP-Ni, O-2-PIMP-Cu, O-2-PIMP-Cr, O-2-PIMP-Pb, and O-2-PIMP-Zn were found to be 100.00%, 79.09%, 68.28%, 65.97%, 51.33%, 70.14%, 54.13% and 66.77%, respectively, at 1000°C by using TG analyses.