Synthesis and spectral analysis of N-substituted pyrrole salicylaldehyde derivatives-electropolymerization of a new nickel(II)-Schiff base complex derived from 6-[3′-N-pyrrolpropoxy]-2-hydroxyacetophenone and 1,2-diaminoethane

Three dihydroxylated acetophenone derivatives 2,6-( 1a ), 2,5-( 2a ), and 2,4-dihydroxyacetophenone ( 3a ) were O-monoalkylated at moderate temperature (50 °C) using 3-bromopropyl-N-pyrrole. These monomers 6-(3′- N -pyrrolpropoxy)-2-hydroxyacetophenone ( 1b ), 5-(3′- N -pyrrolpropoxy)-2-hydroxyacetophenone ( 2b ), and 4-(3′- N -pyrrolpropoxy)-2-hydroxy acetophenone ( 3b ) were isolated with acceptable yields ( 59–70 %). Their characterization was carried out with usual spectroscopic methods such as UV–vis, FTIR, NMR 1 H, 13 C, Dept135, and elemental analysis. These pyrrolic compounds were deliberately chosen as electropolymerizable monomers to elaborate poly(pyrrole) films containing metallic centers useful as redox mediators covalently grafted on the surfaces of modified electrodes. Accordingly, we have initiated the synthesis of an original pyrrole-Ni(II)-Schiff base complex derived from 2,6-( 1b ) and 1,2-diaminoethane. This pyrrolic complex was electropolymerized onto glassy carbon (GC), platinum disk (Pt), and indium tin oxide (ITO) electrode surfaces. This electropolymerization was performed in acetonitrile via anodic oxidation of pyrrolic moieties by cyclic voltammetry. The efficiency of the electrochemical polymerization was investigated as a function of several parameters such as the nature of the electrode material, the number of voltammetric scans, and the scan rate dependence. The electrodeposited poly(pyrrole) films onto ITO surface was characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). This poly(pyrrole) matrix, containing metallic centers, was found to have good catalytic properties towards the reduction of iodobenzene and carbon dioxide CO 2 . Graphical abstract