title: Radical ions from 3,3''',3''''-tris(butylsulfanyl)- 2,2':5',2'':5'',2''',5''',2'''':5'''',2'''''-sexithiophene: an experimental and theoretical study of the p- and n-doped oligomer.
abstract: The 3,3''',3'''''-tris(butylsulfanyl)- 2,2':5',2'':5'',2''',5''',2'''':5'''',2'''''-sexithiophene 1 was investigated through spectroscopic (NMR, EPR, UV/Vis-NIR), electrochemical, spectroelectrochemical and theoretical (DFT) studies. The charged species obtained upon its oxidation and reduction were characterised, showing that 1 can exist in at least five different oxidation states, that is, a neutral species, a radical cation, a dication, a radical anion, and a dianion. The long term stability of the radical cation 1+. was evidenced by the 1H NMR study in the presence of small quantities of trifluoroacetic acid (TFA). This approach allowed a comparison of the relative broadening of proton signals of 1, induced by the electron exchange process with traces of radical cation 1+., and the hfc (hyperfine coupling) constants obtained from the EPR study and DFT calculations. In the radical cation, all of the heterocyclic sulphur atoms are not significantly involved in the delocalisation of the unpaired electron, whereas the opposite holds for the radical anion. Time-dependent DFT calculations reproduced well the wavelengths of the optical transitions observed in the spectroelectrochemical experiments for all the five oxidation states and support the formation of the dianion 1(2-).
authors.affiliation: Istituto per la Sintesi e la Fotoreattività ISOF-CNR, Via P. Gobetti 101, 40129 Bologna, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Alberti
authors.forename: Barbara
authors.initials: B
authors.lastname: Ballarin
authors.forename: Maurizio
authors.initials: M
authors.lastname: Guerra
authors.forename: Dante
authors.initials: D
authors.lastname: Macciantelli
authors.forename: Adele
authors.initials: A
authors.lastname: Mucci
authors.forename: Francesca
authors.initials: F
authors.lastname: Parenti
authors.forename: Luisa
authors.initials: L
authors.lastname: Schenetti
authors.forename: Renato
authors.initials: R
authors.lastname: Seeber
authors.forename: Chiara
authors.initials: C
authors.lastname: Zanardi
mesh_terms: D000838:Anions; D001952:Bridged-Ring Compounds / Q000737:chemistry; D002412:Cations; D004563:Electrochemistry / Q000379:methods; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D013455:Sulfur / Q000737:chemistry; D013876:Thiophenes / Q000737:chemistry*; D013997:Time Factors; D014269:Trifluoroacetic Acid / Q000737:chemistry
chemical_list: C490725:3,3''',3'''''-tris(butylsulfanyl)-2,2'-5',2''-5'',2''',5''',2''''-5'''',2'''''-sexithiophene; D000838:Anions; D001952:Bridged-Ring Compounds; D002412:Cations; D005609:Free Radicals; D010714:Phosphatidylethanolamines; D011108:Polymers; D013876:Thiophenes; C094877:dioleoyl phosphatidylethanolamine; D013455:Sulfur; D014269:Trifluoroacetic Acid