Oxidation Pathways Involving a Sulfide-Endcapped Donor–Acceptor–Donor π-Conjugated Molecule and Antimony(V) Chloride

The oxidation pathways and products of a discrete, sulfide-endcapped donor–acceptor–donor (D/A/D) molecule, namely, propylenedioxythiophene–benzothiadiazole–propylenedioxythiophene, are investigated. The electrochemical and chemical oxidations proceed by two distinct routes. Specifically, electrochemical oxidation undergoes a sequential two-step, one-electron (1e–) oxidation route with a 117 mV difference between consecutive half-wave potentials. In contrast, chemical oxidation by antimony(V) chloride (SbCl5) causes the generation of four different oxidized species: (a) the 1e– oxidation state, (b) a decomposition product, (c) the 2e– oxidation state, and (d) a chloride adduct of the 2e– oxidation state. The decomposition product is generated by the reaction of the 1e– oxidation state with residual water, resulting in nucleophilic aromatic substitution at the sulfide group terminal positions. This reaction leads to the formation of a 2e– oxidized, oxygen atom (ketone) terminated decomposed molecule. The c...