Electrochemical and optical properties of new electrochromic and fluorescent nitrobenzoyl polypyrrole derivatives

摘要

Two new nitrobenzoyl pyrrole derivatives, 4"-nitrobenzoyl (pyrrole-1'-yl)-1-propylate (NPy) and 3",5"-dinitrobenzoyl (pyrrole-1'-yl)-1-propylate (DNPy), were synthesized and successfully polymerized by chemical and electrochemical routes. Optical and electrochemical properties of the monomers and polymers were investigated. Both conducting polymers, electrochemically prepared in 0.1 mol L~(-1) TBABF_4/ACN, were deposited onto platinum, glassy carbon or ITO electrodes and showed well-defined reversible redox processes centered around +0.65 V vs. Ag/AgCl (KCl sat.). Cyclic voltammetric studies revealed well adherent films on the electrode surface (Pt, GC, ITO). The polymer films also exhibited electrochromic behavior with color changes from pale green (reduced state) to dark grey (oxidized state), and also a significant absorbance in the infrared region (oxidized state). The monomers and respective polymers are fluorescent, with emission bands at λ_(em) = 501 nm for NPy, λ_(em) = 515 nm for DNPy and λ_(em) = 438 nm for both PNPy and PDNPy, in THF. The monomers also present fluorescence in the solid state. The HOMO and LUMO energy levels were calculated from UV-Vis (λ_(onset)) and redox potentials (E_(red/ox)~(onset)) data.