[en] Density functional theory calculations together with highly resolved gas-phase ultraviolet photoelectron spectroscopy have been applied to oligothiophene chains with up to eight thiophene rings. One of the important parameters governing the charge transport properties in the condensed phase is the amount of energy relaxation upon ionization. Here, we investigate the impact on this parameter of the backbone flexibility present in oligothiophenes as a result of inter-ring torsional motions. With respect to oligoacenes that are characterized by a coplanar and rigid backbone, the torsional flexibility in oligothiophenes adds to the relaxation energy and leads to the broadening of the first ionization peak, making its analysis more complex.
Baitoul, M., Wery, J., Buisson, J. P., Arbuckle, G., Shah, H., Lefrant, S. & Hamdoume, M. 2000 In situ resonant Raman and optical investigations of p-doped poly(p-phenylene vinylene). Polymer 41, 6955-6964. (doi:10.1016/S0032-3861(00)00022-7)
Bao, Z. N., Feng, Y., Dodabalapur, A., Raju, V. R. & Lovinger, A. J. 1997 High-performance plastic transistors fabricated by printing techniques. Chem. Mater. 9, 1299-1301. (doi:10.1021/cm9701163)
Becke, A. D. 1988 Density-functional exchange-energy approximation with correct asymptoticbehavior. Phys. Rev. A 38, 3098-3100. (doi:10.1103/PhysRevA.38.3098)
Becke, A. D. 1993a Density-functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 98, 5648-5652. (doi:10.1063/1. 464913)
Becke, A. D. 1993b A new mixing of Hartree-Fock and local-density- functional theories. J. Chem. Phys. 98, 1372-1377. (doi:10.1063/1.464304)
Bredas, J. L. & Street, G. B. 1985 Polarons, bipolarons, and solitons in conducting polymers. Acc. Chem. Res. 18, 309-315. (doi:10.1021/ar00118a005)
Bredas, J. L., Beljonne, D., Coropceanu, V. & Cornil, J. 2004 Charge-transfer and energy-transfer processes in π-conjugated oligomers and polymers: a molecular picture. Chem. Rev. 104, 4971-5003. (doi:10.1021/cr040084k)
Casado, J. et al. 2002 Combined spectroelectrochemical and theoretical study of a vinylene-bridged sexithiophene cooligomer: analysis of the p-electron delocalization and of the electronic defects generated upon doping. J. Phys. Chem. 5106, 3872-3881. (doi:10.1021/jp0145210)
Casado, J., Pappenfus, T. M., Mann, K. R., Milian, B., Orti, E., Viruela, P. M., Ruiz Delgado, M. C., Hernandez, V. & Lopez Navarrete, J. T. 2003 UV-Vis, IR, Raman and theoretical characterization of a novel quinoid oligothiophene molecular material. J. Mol. Struct. 651-653, 665-673. (doi:10.1016/S0022-2860(02)00691-9)
Chesterfield, R. J., Newman, C. R., Pappenfus, T. M., Ewbank, P. C., Haukaas, M. H., Mann, K. R., Miller, L. L. & Frisbie, C. D. 2003 High electron mobility and ambipolar transport in organic thin-film transistors based on a pi-stacking quinoidal terthiophene. Adv. Mater. 15, 1278-1282. (doi:10.1002/adma.200305200)
Chong, D. P., Gritsenko, O. V. & Baerends, E. J. 2002 Interpretation of the Kohn-Sham orbital energies as approximate vertical ionization potentials. J. Chem. Phys. 116, 1760-1772. (doi:10.1063/1.1430255)
Cornil, J., Beljonne, D. & Bredas, J. L. 1995 Nature of optical-transitions in conjugated oligomers. 1. Theoretical characterization of neutral and doped oligo(phenylenevinylene)s. J. Chem. Phys. 103, 834-841. (doi:10.1063/1.470116)
Cornil, J., Calbert, J. P. & Bredas, J. L. 2001 Electronic structure of the pentacene single crystal: relation to transport properties. J. Am. Chem. Soc. 123, 1250-1251. (doi:10.1021/ja005700i)
Coropceanu, V., Malagoli, M., da Silva Filho, D. A., Gruhn, N. E., Bill, T. G. & Bredas, J. L. 2002a Hole- and electron-vibrational couplings in oligoacene crystals: intramolecular contributions. Phys. Rev. Lett. 89, 275503. (doi:10.1103/PhysRevLett.89.275503)
Coropceanu, V., Malagoli, M., da Silva Filho, D. A., Gruhn, N. E., Bill, T. G. & Bredas, J. L. 20026 Hole- and electron-vibrational couplings in oligoacene crystals: intramolecular contributions. Phys. Rev. Lett. 89, 275503/1-275503/4. (doi:10.1103/PhysRevLett.89.275503)
Coropceanu, V., Kwon, O., Wex, B., Kaafarani, B. R., Gruhn, N. E., Durivage, J. C., Neckers, D. C. & Bredas, J. L. 2006 Vibronic coupling in organic semiconductors: the case of fused polycyclic benzene-thiophene structures. Chem. Eur. J. 12, 2073-2080. (doi:10.1002/chem. 200500879)
da Silva, D. A. et al. 2004 Vibronic coupling in the ground and excited states of the naphthalene cation. Chem. Commun. 1702-1703. (doi:10.1039/b403828b)
da Silva, D. A., Kim, E. G. & Bredas, J. L. 2005 Transport properties in the rubrene crystal: electronic coupling and vibrational reorganization energy. Adv. Mater. 17, 1072-1076. (doi:10.1002/adma.200401866)
de Wijs, G. A., Mattheus, C. C., de Groot, R. A. & Palstra, T. T. M. 2003 Anisotropy of the mobility of pentacene from frustration. Synth. Met. 139, 109-114. (doi:10.1016/S0379-6779(03)00020-1)
Diaz-Quijada, G. A., Weinberg, N., Holdcroft, S. & Pinto, B. M. 2002 Investigation of barriers to conformational interchange in oligothiophenes and oligo(thienyl)furans. J. Phys. Chem. A 106, 1266-1276. (doi:10.1021/jp011783t)
Dimitrakopoulos, C. D. & Malenfant, P. R. L. 2002 Organic thin film transistors for large area electronics. Adv. Mater. 14, 99-117. (doi:10.1002/1521-4095(20020116)14:2〈99::AID-ADMA99〉3.0.CO;2-9)
Ditchfield, R., Hehre, W. J. & Pople, J. A. 1971 Self-consistent molecular-orbital methods. 9. Extended Gaussian-type basis for molecular-orbital studies of organic molecules. J. Chem. Phys. 54, 724-728. (doi:10.1063/1.1674902)
Facchetti, A., Mushrush, M., Yoon, M. H., Hutchison, G. R., Ratner, M. A. & Marks, T. J. 2004a Building blocks for n-type molecular and polymeric electronics. Perfluoroalkyl- versus alkylfunctionalized oligothiophenes (nT; n=2-6). Systematics of thin film microstructure, semiconductor performance, and modeling of majority charge injection in field-effect transistors. J. Am. Chem. Soc. 126, 13859-13874. (doi:10.1021/ja0489846)
Facchetti, A., Yoon, M. H., Stern, C. L., Hutchison, G. R., Ratner, M. A. & Marks, T. J. 2004b Building blocks for N-type molecular and polymeric electronics, perfluoroalkyl- versus alkylfunctionalized ligothiophenes (nTs; n=2-6). Systematic synthesis, spectroscopy, electrochemistry, and solid-state organization. J. Am. Chem. Soc. 126, 13480-13501. (doi:10.1021/ja048988a)
Fichou, D. 1999 Handbook of oligo- and polythiophenes. Weinheim, Germany; New York, NY: Wiley-VCH.
Fichou, D. 2000 Structural order in conjugated oligothiophenes and its implications on optoelectronic devices. J. Mater. Chem. 10, 571-588. (doi:10.1039/a908312j)
Frisch, M. J. et al. 1998 GAUSSIAN98. Gaussian 98 (Revision A.11). Pittsburgh, PA: Gaussian, Inc.
Geskin, V. M. & Bredas, J.-L. 2003 Polaron pair versus bipolaron on oligothiophene chains: a theoretical study of the singlet and triplet states. Chem. Phys. Chem. 4, 498-505. (doi:10.1002/cphc.200200446)
Geskin, V. M., Dkhissi, A. & Bredas, J. L. 2003 Oligothiophene radical cations: polaron structure in hybrid DFT and MP2 calculations. Int. J. Quantum Chem. 91, 350-354. (doi:10.1002/qua.10436)
Gierschner, J., Mack, H. G., Luer, L. & Oelkrug, D. 2002 Fluorescence and absorption spectra of oligophenylenevinylenes: vibronic coupling, band shapes, and solvatochromism. J. Chem. Phys. 116, 8596-8609. (doi:10.1063/1.1469612)
Gierschner, J., Cornil, J. & Egelhaaf, H.-J. 2006 Optical bandgaps of p-conjugated organic materials at the polymer limit: experiment and theory. Adv. Mater. 19, 173-191. (doi:10.1002/adma.200600277)
Gordon, M. S. 1980 The isomers of silacyclopropane. Chem. Phys. Lett. 76, 163-168. (doi:10.1016/0009-2614(80)80628-2)
Grozema, F. C., van Duijnen, P. T., Berlin, Y. A., Ratner, M. A. & Siebbeles, L. D. A. 2002 Intramolecular charge transport along isolated chains of conjugated polymers: effect of torsional disorder and polymerization defects. J. Phys. Chem. 5106, 7791-7795. (doi:10.1021/jp021114v)
Gruhn, N. E., da Silva, D. A., Bill, T. G., Malagoli, M., Coropceanu, V., Kahn, A. & Bredas, J. L. 2002 The vibrational reorganization energy in pentacene: molecular influences on charge transport. J. Am. Chem. Soc. 124, 7918-7919. (doi:10.1021/ja0175892)
Haddon, R. C., Chi, X., Itkis, M. E., Anthony, J. E., Eaton, D. L., Siegrist, T., Mattheus, C. C. & Palstra, T. T. M. 2002 Band electronic structure of one- and two-dimensional pentacene molecular crystals. J. Phys. Chem. B 106, 8288-8292. (doi:10.1021/jp0207937)
Hariharan, P. C. & Pople, J. A. 1973 Influence of polarization functions on molecular-orbital hydrogenation energies. Theor. Chim. Acta 28, 213-222. (doi:10.1007/BF00533485)
Hariharan, P. C. & Pople, J. A. 1974 Accuracy of Ah equilibrium geometries by single determinant molecular-orbital theory. Mol. Phys. 27, 209-214. (doi:10.1080/00268977400100171)
Heeney, M., Bailey, C., Genevicius, K., Shkunov, M., Sparrowe, D., Tierney, S. & McCulloch, I. 2005 Stable polythiophene semiconductors incorporating thieno[2,3-b]thiophene. J. Am. Chem. Soc. 127, 1078-1079. (doi:10.1021/ja043112p)
Hehre, W. J., Ditchfield, R. & Pople, J. A. 1972 Self-consistent molecular-orbital methods. 12. Further extensions of Gaussian-type basis sets for use in molecular-orbital studies of organic-molecules. J. Chem. Phys. 56, 2257-2261. (doi:10.1063/1.1677527)
Heimel, G., Daghofer, M., Gierschner, J., List, E. J. W., Grimsdale, A. C., Mullen, K., Beljonne, D., Bredas, J. L. & Zojer, E. 2005 Breakdown of the mirror image symmetry in the optical absorption/emission spectra of oligo(poro-phenylene)s. J. Chem. Phys. 122, 054 501. (doi:10.1063/1.1839574)
Horowitz, G., Garnier, F., Yassar, A., Hajlaoui, R. & Kouki, F. 1996 Field-effect transistor made with a sexithiophene single crystal. Adv. Mater. 8, 52-54. (doi:10.1002/adma.19960080109)
Hutchison, G. R., Ratner, M. A. & Marks, T. J. 2005 Hopping transport in conductive heterocyclic oligomers: reorganization energies and substituent effects. J. Am. Chem. Soc. 127, 2339-2350. (doi:10.1021/ja0461421)
Iwanaga, H., Naito, K. & Effenberger, F. 2000 Oligothiophene dyes for guest-host liquid crystal displays. Liq. Cryst. 27, 115-123. (doi:10.1080/026782900203281)
Jones, D., Guerra, M., Favaretto, L., Modelli, A., Fabrizio, M. & Distefano, G. 1990 Determination of the electronic-structure of thiophene oligomers and extrapolation to polythiophene. J. Phys. Chem. 94, 5761-5766. (doi:10.1021/j100378a030)
Jurchescu, O. D., Baas, J. & Palstra, T. T. M. 2004 Effect of impurities on the mobility of single crystal pentacene. Appl. Phys. Lett. 84, 3061-3063. (doi:10.1063/1.1704874)
Katz, H. E., Bao, Z. N. & Gilat, S. L. 2001 Synthetic chemistry for ultrapure, processable, and high-mobility organic transistor semiconductors. Acc. Chem. Res. 34, 359-369. (doi:10.1021/ar990114j)
Koopmans, T. 1933 The distribution of wave function and characteristic value among the individual electrons of an atom. Physica (The Hague) 1, 104-113. (doi:10.1016/S0031-8914(34)90011-2)
Kwon, O., Coropceanu, V., Gruhn, N. E., Durivage, J. C., Laquindanum, J. G., Katz, H. E., Cornil, J. & Bredas, J. L. 2004 Characterization of the molecular parameters determining charge transport in anthradithiophene. J. Chem. Phys. 120, 8186-8194. (doi:10.1063/1.1689636)
Lee, C., Yang, W. & Parr, R. G. 1988 Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. Phys. Rev. B: Condens. Matter 37, 785-789. (doi:10.1103/PhysRevB.37.785)
Lichtenberger, D. L. & Copenhaver, A. S. 1990 Ionization band profile analysis in valence photoelectron-spectroscopy. J. Electron. Spectrosc. Relat. Phenom. 50, 335-352. (doi:10.1016/0368-2048(90)87076-Z)
Lichtenberger, D. L., Kellogg, G. E., Kristofzski, J. G., Page, D., Turner, S., Klinger, G. & Lorenzen, J. 1986 Inexpensive and high-precision digital power-supply and counting interface for UPS, XPS, and Auger spectrometers. Rev. Sci. Instrum. 57, 2366. (doi:10.1063/1. 1139199)
Malagoli, M., Coropceanu, V., da Silva, D. A. & Bredas, J. L. 2004 A multimode analysis of the gas-phase photoelectron spectra in oligoacenes. J. Chem. Phys. 120, 7490-7496. (doi:10.1063/1.1687675)
Mazzeo, M., Pisignano, D., Favaretto, L., Barbarella, G., Cingolani, R. & Gigli, G. 2003 Bright oligothiophene-based light emitting diodes. Synth. Met. 139, 671-673. (doi:10.1016/S0379-6779(03)00304-7)
Mazzeo, M., Vitale, V., Della Sala, F., Anni, M., Barbarella, G., Favaretto, L., Sotgiu, G., Cingolani, R. & Gigli, G. 2005 Bright white organic light-emitting devices from a single active molecular material. Adv. Mater. 17, 34-39. (doi:10.1002/adma.200400670)
Meier, H., Stalmach, U. & Kolshorn, H. 1997 Effective conjugation length and UV/vis spectra of oligomers. Acta Polym. 48, 379-384. (doi: 10.1002/actp.1997.010480905)
Merlo, J. A. & Frisbie, C. D. 2003 Field effect conductance of conducting polymer nanofibers. J. Polym. Sci. Part B: Polym. Phys. 41, 2674-2680. (doi:10.1002/polb.10656)
Merlo, J. A., Newman, C. R., Gerlach, C. P., Kelley, T. W., Muyres, D. V., Fritz, S. E., Toney, M. F. & Frisbie, C. D. 2005 p-Channel organic semiconductors based on hybrid acenethiophene molecules for thin-film transistor applications. J. Am. Chem. Soc. 127, 3997-4009. (doi:10.1021/ja044078h)
Newman, C. R., Frisbie, C. D., da Silva Filho, D. A., Bredas, J. L., Ewbank, P. C. & Mann, K. R. 2004 Introduction to organic thin film transistors and design of n-channel organic semiconductors. Chem. Mater. 16, 4436-4451. (doi:10.1021/cm049391x)
Ong, B., Wu, Y. L., Jiang, L., Liu, P. & Murti, K. 2004 Polythiophene-based field-effect transistors with enhanced air stability. Synth. Met. 142, 49-52. (doi:10.1016/j.synthmet.2003.07.004)
Pappenfus, T. M., Chesterfield, R. J., Frisbie, C. D., Mann, K. R., Casado, J., Raff, J. D. & Miller, L. L. 2002a A pi-stacking terthiophene-based quinodimethane is an n-channel conductor in a thin film transistor. J. Am. Chem. Soc. 124, 4184-4185. (doi:10.1021/ ja025553j)
Pappenfus, T. M., Raff, J. D., Hukkanen, E. J., Burney, J. R., Casado, J., Drew, S. M., Miller, L. L. & Mann, K. R. 20026 Dinitro and quinodimethane derivatives of terthiophene that can be both oxidized and reduced. Crystal structures, spectra, and a method for analyzing quinoid contributions to structure. J. Org. Chem. 67, 6015-6024. (doi:10.1021/jo025572b)
Pisignano, D., Persano, L., Mele, E., Visconti, P., Cingolani, R., Gigli, G., Barbarella, G. & Favaretto, L. 2005 Emission properties of printed organic semiconductor lasers. Opt. Lett. 30, 260-262. (doi:10.1364/OL.30.000260)
Reimers, J. R. 2001 A practical method for the use of curvilinear coordinates in calculations of normal-mode-projected displacements and Duschinsky rotation matrices for large molecules. J. Chem. Phys. 115, 9103-9109. (doi:10.1063/1.1412875)
Roncali, J. 2005 Linear pi-conjugated systems derivatized with C-60-fullerene as molecular heterojunctions for organic photovoltaics. Chem. Soc. Rev. 34, 483-495. (doi:10.1039/b415941c)
Rubio, M., Merchan, M., Pou-Amerigo, R. & Orti, E. 2003 The low-lying excited states of 2,2′-bithiophene: a theoretical analysis. Chemphyschem 4, 1308-1315. (doi:10.1002/cphc.200300790)
Sánchez-Carrera, R. S., Coropceanu, V., da Silva Filho, D. A., Friedlein, R., Osikowicz, W., Murdey, R., Suess, C., Salaneck, W. R. & Bredas, J. L. 2006 Vibronic coupling in the ground and excited states of oligoacene cations. J. Phys. Chem. B 110, 18 904-18 911. (doi:10.1021/jp057462p)
Telesca, R., Bolink, H., Yunoki, S., Hadziioannou, G., Van Duijnen, P. T., Snijders, J. G., Jonkman, H. T. & Sawatzky, G. A. 2001 Density-functional study of the evolution of the electronic structure of oligomers of thiophene: towards a model Hamiltonian. Phys. Rev. 56315, 155 112. (doi:10.1103/PhysRevB.63.155112)
Torsi, L., Lovinger, A. J., Crone, B., Someya, T., Dodabalapur, A., Katz, H. E. & Gelperin, A. 2002 Correlation between oligothiophene thin film transistor morphology and vapor responses. J. Phys. Chem. B 106, 12563-12568. (doi:10.1021/jp021473q)
Viruela, P. M., Viruela, R. & Orti, E. 1998 Difficulties of density functional theory in predicting the torsional potential of 2,2′- bithiophene. M. J. Quantum Chem. 70, 303-312. (doi:10.1002/(SICI) 1097-461X(1998)70:2〈303::AID-QUA6〉3.0.CO;2-Y)
Zavelani-Rossi, M., Lanzani, G., Anni, M., Gigli, G., Cingolani, R., Barbarella, G. & Favaretto, L. 2003 Organic laser based on thiophene derivatives. Synth. Met. 139, 901-903. (doi:10.1016/S0379-6779(03) 00298-4)
