title: Neutral and oxidized triisopropylsilyl end-capped oligothienoacenes: a combined electrochemical, spectroscopic, and theoretical study.
abstract: This work presents an analysis of the structural, electrochemical, and optical properties of a family of triisopropylsilyl end-capped oligothienoacenes (TIPS-Tn-TIPS, n=4-8) by combining cyclic voltammetry, spectroscopic techniques, and quantum-chemical calculations. TIPS-Tn-TIPS compounds form stable radical cations, and dications are only obtained for the longest oligomers (n=7 and 8). Oxidation leads to the quinoidization of the conjugated backbone, from which electrons are mainly extracted. The absorption and fluorescence spectra show partially resolved vibronic structures even at room temperature, due to the rigid molecular geometry. Two well-resolved vibronic progressions are observed at low temperatures due to the vibronic coupling, with normal modes showing wavenumbers of approximately 1525 and approximately 480 cm(-1). Optical absorption bands display remarkable bathochromic dispersion with the oligomer length, indicative of the extent of pi conjugation. The optical properties of the oxidized compounds are characterized by in situ UV/Vis/NIR spectroelectrochemistry. The radical cation species show two intense absorption bands emerging at energies lower than in the neutral compounds. The formation of the dication is only detected for the heptamer and the octamer, and shows a new band at intermediate energies. Optical data are interpreted with the help of density functional theory calculations performed at the B3LYP/6-31G** level, both for the neutral and the oxidized compounds.
authors.affiliation: Instituto de Ciencia Molecular, Universidad de Valencia, Valencia 46980, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Aragó
authors.forename: Pedro M
authors.initials: PM
authors.lastname: Viruela
authors.forename: Enrique
authors.initials: E
authors.lastname: Ortí
authors.forename: Reyes
authors.initials: R
authors.lastname: Malavé Osuna
authors.forename: Barbara
authors.initials: B
authors.lastname: Vercelli
authors.forename: Gianni
authors.initials: G
authors.lastname: Zotti
authors.forename: Víctor
authors.initials: V
authors.lastname: Hernández
authors.forename: Juan T
authors.initials: JT
authors.lastname: López Navarrete
authors.forename: John T
authors.initials: JT
authors.lastname: Henssler
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Matzger
authors.forename: Yoshitake
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Yamaguchi