Electropolymerization of Oligothienylferrocene Complexes:  Spectroscopic and Electrochemical Characterization

Abstract

The new complexes 1,1′-bis(5-(2,2′-bithienyl))ferrocene (2) and 1,1′-bis(5-(2,2′:5′,2′′-terthienyl))ferrocene (3) have been synthesized by coupling 1,1′-bis(2-thienyl)ferrocene (1) with 2-bromothiophene and 5-bromo-2,2′-bithiophene, respectively. The cyclic voltammograms of 1-3 contain a reversible Fe II/III wave with E 1/2 between 0.37 and 0.46 V vs SCE and irreversible thiophene-based oxidation waves at higher potentials. These compounds can be electrochemically oxidized to yield solutions of the monocations 1 + -3 + . The visible-near-IR spectra of these monocations all contain low-energy bands due to an oligothienyl group to Fe III charge-transfer transition. The absorption maxima and intensities of these bands correlate to the length of the conjugation in the oligothienyl group. Above the thiophene oxidation potential and by careful exclusion of water, 2 and 3 electropolymerize resulting in the deposition of electrochromic films on the electrode surface. The films are golden-red and stable when neutral and become black upon oxidation. The cyclic voltammetry of the film growth process and the formation of electroactive films indicate that the films are conductive. Spectroelectrochemical characterization of the films demonstrates that broad, low-energy absorptions appear upon oxidation of the ferrocenyl centers and that stronger and much broader bands appear upon full oxidation of the films.

Organometallic Ferrocene- and Phosphorus-Containing Polymers: Synthesis and Characterization

“…Conducting polymers containing ferrocene on main conjugation path of polymer backbone were also synthesized [54,55]. Electrochemical experiments revealed that the ferrocene clicked PEDOT films have fast electron transfer ability and spectroelectrochemical studies show that the conducting polymer can switch from opaque purple to red then blue [56]. Ferrocene substituted donor-acceptor-donor type polymer; poly (5,8-…”

Transition-Metal-Polythiophene Hybrid Materials

“…The ruthenium oligothienylacetylide complexes 31 have been electropolymerized by our group, [51] as have the oligothienylferrocene complexes 32a, b. [52] The voltammetry of films of poly-32a and poly-32b revealed redox waves due to both the ferrocene and backbone redox couples. Spectroelectrochemical experiments on these films show that low-energy absorption bands appear upon oxidation of both the Fe centers and the conjugated backbone, and these have been attributed to charge-transfer processes in these materials.…”

Structure‐Dependent Electrochemical Behavior of Thienylplatinum(II) Complexes of N,N‐Heterocycles

“…This behavior is consistent with the formation of electroactive or conductive polymers or high oligomers. [17] Since these species are less readily soluble in the analyte solution, their formation would alter the redox pattern of the sample, and eventually render the analyte featureless in the CV scans. Polymerization is likely to take place at the thienyl site since electropolymerization of thiophene, bithiophene and substituted thiophenes is common.…”