6533b7d4fe1ef96bd1262978

RESEARCH PRODUCT

Neutral and oxidized triisopropylsilyl end-capped oligothienoacenes: a combined electrochemical, spectroscopic, and theoretical study.

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This work presents an analy- sis of the structural, electrochemical, and optical properties of a family of triisopropylsilyl end-capped oligothie- noacenes (TIPS-Tn-TIPS, n = 4-8) by combining cyclic voltammetry, spectro- scopic techniques, and quantum-chemi- cal calculations. TIPS-Tn-TIPS com- pounds form stable radical cations, and dications are only obtained for the lon- gest oligomers (n = 7 and 8). Oxidation leads to the quinoidization of the con- jugated backbone, from which elec- trons are mainly extracted. The absorp- tion and fluorescence spectra show par- tially 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 � 1525 and � 480 cm � 1 . Optical absorption bands display remarkable bathochromic dis- persion with the oligomer length, indi- cative of the extent of p conjugation. The optical properties of the oxidized compounds are characterized by in situ UV/Vis/NIR spectroelectrochemistry. The radical cation species show two in- tense absorption bands emerging at en- ergies lower than in the neutral com- pounds. 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 per- formed at the B3LYP/6-31G** level, both for the neutral and the oxidized compounds.