Synthesis and electropolymerization of new phenylene-substituted dipyrridyls. Electrochemical and spectroscopic characterization of the resulting polymers
Résumé
The present paper sets out the synthesis and electropolymerization process of 1,1’-phenylenedipyrridyl (PhDPy) and 1,1’-diphenylenedipyrridyl (DPhDPy). These compounds are prepared by Clauson-Kaas methods with 35 or 71 % yield and characterized. UV-VIS electronic absorption spectra and electrochemical methods were used to examine the effects of the electronic π-system extension in PhDPy and DPhDPy structures on the monomer properties relative to N-phenylpyrrole (N-PhPy). Also, PhDPy and DPhDPy were electropolymerized on platinum electrode by anodic oxidation in 0.1 M tetrabutylammonium hexafluorophosphate (Bu4NPF6) acetonitrile or dichloromethane solutions and characterized by electrochemical and spectroscopic techniques. The electronic π-system extension effects on the poly(PhDPy) physicochemical properties and structure were investigated by cyclic voltammetry (CV), FT-IR, UV-VIS and XPS spectroscopy and scanning electron microscopy (SEM). CV of the poly (PhDPy) films indicated a good redox behavior and an improvement of the electrochemical properties. FT-IR spectral studies indicated a linear structure of this polymer with 2,5 coupling on the pyrrole ring. SEM analysis showed that polymer film morphology changed between the oxidized and reduced states. The solid-state UV-VIS spectra of the poly(PhDPy) films on ITO were characterized by a significant red-shift of the absorption maximum, as compared to poly(N-PhPy) film. Moreover, the very low amount of poly(DPhDPy) film obtained during the electropolymerization process and electrochemical studies of electrosynthesized poly(DPhDPy) showed that the polymer properties modulated by extension of the monomer electronic π-system can be limited by steric effects.