Photochemical and Electrochemical Oxygenation of Thiophenes, Benzo[b]Thiophenes and Dibenzothiophenes; Photochemical and Electrochemical Behaviour of Their Oxygenated Intermediates and Products

Abstract

Prof. Dr. Thies Thiemann received his chemical education at the universities of Hamburg and Tuebingen, Germany. After obtaining a PhD degree in organic chemistry at the University of Hamburg, he moved to Japan for his postdoctorate at Kyushu University, Fukuoka. Thies has also worked at joined the chemistry faculty of the United Arab Emirates University in Al Ain, Abu Dhabi. His main focus is on organic synthetic chemistry, especially in the areas of steroidal and heterocyclic chemistry. He is author/co-author of over 150 papers, nine reviews, three book chapters and five patents. S-oxides and benzo[b]thiopheneS,S-dioxides 672 6. Photochemistry of thiophene S-oxides 675 7. Electrochemical oxidation and reduction of thiophenes, thiophene S-oxides and related compounds 675 8. Conclusions 676 9. References 678The photooxygenation of thiophenes, benzo[b]thiophenes and dibenzothiophenes is discussed, especially in view of the oxidative removal of these S-containing contaminants from fuels. Furthermore, the photochemistry of the intermediates and the products from these processes is detailed. Finally, an account is given of the electrooxidation of thiophenes and derivatives to the corresponding sulfoxides and sulfones as well as of the electrochemical behaviour of the intermediate thiophene S-oxides.

Matter of minutes degradation of poly(3-hexylthiophene) under illumination in air

“…30) have shown that illuminated P3HT, like many organic chromophores, is indeed a generator of singlet oxygen. In the same publication however, Manceau et al demonstrated that singlet oxygen is very unreactive with polythiophene, as has been suggested elsewhere, 40 hence singlet oxygen is not thought to go on to react to form an oxygenated defect state with P3HT, as marked out in the scheme. The most likely route for oxygenated defect formation therefore is by direct conversion from the charge transfer intermediate state.…”

“…Of the polymer degradation studies available, studies have primarily focused on the prevalent polyphenylvinylene (PPV) [24][25][26][27][28][29] and polythiophene (PT) 26,[29][30][31][32][33][34][35][37][38][39][40] family of polymers. A degradation pathway for conjugated polymers that is well supported by studies is oxidation via radical formation.…”

“…41,42 Reaction with ozone (O 3 ) is also considered to efficiently degrade conjugated polymers, [42][43][44] however it is still unclear whether its concentration in air is sufficient for ozone to be considered a relevant source of degradation. Similarly, a few reports have highlighted the role of singlet oxygen, an unstable high-energy form of ground state oxygen and a well known oxidising agent of organic compounds, 40,45,46 in the degradation of polymers. More recent results however suggest some conjugated polymers, such as polythiophene, may be unreactive to singlet oxygen.…”

Distinguishing photo-induced oxygen attack on alkyl chain versus conjugated backbone for alkylthienyl-benzodithiophene (BDTT)-based push–pull polymers

“…The products could be either a mono-or di-oxidized sulfur atom. [61][62][63] The S-O products are more likely to occur on thiophenes that are a part of a larger conjugated system, such as benzodithiophene, than those that are more isolated due to lower energy barriers. 61 Combining these results, Fig.…”