Simultaneous novel synthesis of conducting and non-conducting halogenated polymers by electroinitiation of (2,4,6-trichloro- or 2,6-dichlorophenolato)Ni(II) complexes

Abstract

NiL 2(Ph) 2· xH 2O [L=3,5-dimethylpyrazole or N-methyl imidazole; Ph=DCP or TCP; x=0, 1 or 3] complexes were synthesised and characterised by analytical and spectroscopic methods using elemental analysis and FTIR. The electrochemical behavior of the complexes was studied by cyclic voltammetry in tetrabutylammoniumtetrafluoroborate– N, N-dimethylformamide electrolyte–solvent couple. Cyclic voltammogram of the complexes displayed two-step oxidation processes under the nitrogen gas atmosphere. The polymerization of the complexes was accomplished in the same solvent–electrolyte couple by the constant potential electrolysis of NiL 2(Ph) 2· xH 2O, synthesizing the poly(di- or monochlorophenylene oxide)s via free radical mechanism. The simultaneous polymerization of non-conducting polymer and conducting polymer (the conductivity of 0.7 S cm −2) were achieved by electroinitiated polymerization of Ni(DMPz) 2(TCP) 2. The structural analysis of the polymers were performed using FTIR, 1H NMR and 13C NMR spectroscopic techniques and DSC for the thermal analysis. The kinetics of the polymerization was followed by in situ UV–vis spectrophotometer during the electrolysis. The low temperature ESR spectrum of the electrolysis solution also confirmed the formation of phenol radical ( g=2.0028). One electron oxidation process of NiL 2(DCP) 2· xH 2O produces a new Ni(II) complex, Ni(L–L)(DCP) 2(S) by the rapid decomposition of Ni IIIL 2(DCP) 2 into a ligand radical producing a singlet with the g value of 2.0015. Second electron oxidation process generates oligemers, which could not be isolated from the electrolyte solution.