TY - JOUR
T1 - Optical, redox, and NLO properties of tricyanovinyl oligothiophenes
T2 - Comparisons between symmetric and asymmetric substitution patterns
AU - Casado, Juan
AU - Delgado, M. Carmen Ruiz
AU - Merchán, M. Carmen Rey
AU - Hernández, Victor
AU - Navarrete, Juan T.López
AU - Pappenfus, Ted M.
AU - Williams, Nathaniel
AU - Stegner, William J.
AU - Johnson, Jared C.
AU - Edlund, Brett A.
AU - Janzen, Daron E.
AU - Mann, Kent R
AU - Orduna, Jesus
AU - Villacampa, Belén
PY - 2006/7/17
Y1 - 2006/7/17
N2 - A series of tricyanovinyl (TCV)-substituted oligothiophenes was synthesized and investigated with a number of physical methods including UV/Vis, IR, and Raman spectroscopy, nonlinear optical (NLO) measurements, X-ray diffraction, and cyclic voltammetry. Mono- or disubstituted oligomers were prepared by the reaction of tetracyanoethylene with monoor dilithiated oligomers. The comparative effects of the symmetric and asymmetric substitutions in the electronic and molecular properties have been addressed. These oligomers display dramatic reductions in both their optical and electrochemical band gaps in comparison with unsubstituted mole-cules. The analysis of the electronic properties of the molecules was assisted by density functional theory calculations, which are in excellent agreement with the experimental data. TCV substitution influences the energies of the frontier orbitals, especially with respect to the stabilization of LUMO orbitals. X-ray structural characterization of a monosubstituted oligomer exhibits π-stacking with favorable intermolecular interactions. NLO results agree with the role of the intramolecular charge-transfer feature in the asymmetric samples. These results furthermore exalt the role of conformational flexibility in the disubstituted compounds and reveal an unexpected nonlinear optical activity for symmetric molecules. Regarding the electronic structure, the interpretation of the vibrational data reflects the balanced interplay between aromatic and quinoid forms, finely tuned by the chain length and substitution pattern. The electronic and structural properties are consistent with the semiconducting properties exhibited by these materials in thin film transistors (TFTs).
AB - A series of tricyanovinyl (TCV)-substituted oligothiophenes was synthesized and investigated with a number of physical methods including UV/Vis, IR, and Raman spectroscopy, nonlinear optical (NLO) measurements, X-ray diffraction, and cyclic voltammetry. Mono- or disubstituted oligomers were prepared by the reaction of tetracyanoethylene with monoor dilithiated oligomers. The comparative effects of the symmetric and asymmetric substitutions in the electronic and molecular properties have been addressed. These oligomers display dramatic reductions in both their optical and electrochemical band gaps in comparison with unsubstituted mole-cules. The analysis of the electronic properties of the molecules was assisted by density functional theory calculations, which are in excellent agreement with the experimental data. TCV substitution influences the energies of the frontier orbitals, especially with respect to the stabilization of LUMO orbitals. X-ray structural characterization of a monosubstituted oligomer exhibits π-stacking with favorable intermolecular interactions. NLO results agree with the role of the intramolecular charge-transfer feature in the asymmetric samples. These results furthermore exalt the role of conformational flexibility in the disubstituted compounds and reveal an unexpected nonlinear optical activity for symmetric molecules. Regarding the electronic structure, the interpretation of the vibrational data reflects the balanced interplay between aromatic and quinoid forms, finely tuned by the chain length and substitution pattern. The electronic and structural properties are consistent with the semiconducting properties exhibited by these materials in thin film transistors (TFTs).
KW - Electronic structure
KW - Oligothiophenes
KW - Photonics semiconductors
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U2 - 10.1002/chem.200501389
DO - 10.1002/chem.200501389
M3 - Article
C2 - 16628759
AN - SCOPUS:33746430488
SN - 0947-6539
VL - 12
SP - 5458
EP - 5470
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 21
ER -