TY - JOUR
T1 - Redox states of long oligothiophenes
T2 - Two polarons on a single chain
AU - Van Haare, John A.E.H.
AU - Havinga, Edsko E.
AU - Van Dongen, Joost L.J.
AU - Janssen, René A.J.
AU - Cornil, Jérôme
AU - Brédas, Jean Luc
PY - 1998
Y1 - 1998
N2 - 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, single-electron oxidation in dichloromethane produces the corresponding radical cations, which form spinless π 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.
AB - 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, single-electron oxidation in dichloromethane produces the corresponding radical cations, which form spinless π 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.
KW - Conducting materials
KW - Oligomers
KW - Pi interactions
KW - Radical ions
KW - Redox chemistry
UR - http://www.scopus.com/inward/record.url?scp=0031877896&partnerID=8YFLogxK
U2 - 10.1002/(sici)1521-3765(19980807)4:8<1509::aid-chem1509>3.0.co;2-%23
DO - 10.1002/(sici)1521-3765(19980807)4:8<1509::aid-chem1509>3.0.co;2-%23
M3 - Article
AN - SCOPUS:0031877896
SN - 0947-6539
VL - 4
SP - 1509
EP - 1522
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 8
ER -