A detailed investigation is presented of the redox states of three oligothiophenes (nT) with 6, 9, and 12 thiophene units. While open-shell radical cations (polarons) and closed-shell dications (bipolarons) are usually invoked as the primary redox species in these systems, we have obtained evidence that the dication of the longest oligothiophene (12T) has an electronic structure with two individual polarons. The redox states of 6T, 9T, and 12T have been fully characterized using UV/visible/near-IR and ESR spectroscopy in combination with electrospray mass spectrometry. For 6T and 9T, singleelectron oxidation in dichloromethane produces the corresponding radical cations, which form spinless p dimers at lower temperatures. A second oxidation step forms dications which possess a bipolaronic electronic structure. However, the redox behavior of the longest oligothiophene, 12T, is entirely different. Radical cations of 12T disproportionate into neutral oligomers and dications, except at the lowest oxidation levels. The spectral data for doubly oxidized 12T are incompatible with those expected for a bipolaronic structure but are consistent with the formation of two individual polarons on a single chain; this interpretation is also supported by the results from correlated quantum chemical calculations.

Extremely effective cooperative effects operate during the formation of chiral stacks of C3‐symmetrical molecules in alkane solvents (a molecule is depicted on the right). The sergeants‐and‐soldiers principles as well as chiral solvation lead to a preferred helical sense in the columnar aggregates. The amplification of chirality in dynamic systems shows the precision in aggregation.

undecithiophenes, the longest characterized oligothiophenesHoeve, ten, W.; Wynberg, H.; Havinga, E.E.; Meijer, E.W.

No abstract