Density functional calculations of potential energy surface and charge transfer integrals in molecular triphenylene derivative HAT6

Zbiri, Mohamed; Johnson, Mark R.; Kearley, Gordon J.; Mulder, Fokko M.

doi:10.1007/s00214-009-0559-3

Cited by 10 publications

(14 citation statements)

References 43 publications

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“…For HAT6 the largest downfield shifts are observed for 13 C nuclei in the outer part of the aromatic core, which is consistent with the spatial distribution of the HOMO. 51,52 However, the observed shifts could correspond to a small amount of intermolecular electron transfer in the ground state of HAT6-TNF. To a first approximation, a unit positive charge on a single carbon induces a downfield shift of about 160 ppm.…”

Section: ■ Resultsmentioning

confidence: 94%

On the Morphology of a Discotic Liquid Crystalline Charge Transfer Complex

et al. 2012

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Discotic liquid crystalline (DLC) charge transfer (CT) complexes, which combine visible light absorption with rapid charge transfer characteristics within the CT complex, can have a great potential for photovoltaic applications when they can be made to self-assemble in a bulk heterojunction arrangement with separate channels for electron and hole conduction. However, the morphology of some liquid crystalline CT complexes has been under debate for many years. In particular, the liquid crystalline CT complex built from the electron acceptor 2,4,7-trinitro-9-fluorenone (TNF) and discotic molecules has been reported to have the TNF "sandwiched" either between the discotic molecules within the same column or between the columns within the aliphatic tails of the discotic molecules. We present a detailed structural study of the prototypic 1:1 mixture of the discotic 2,3,6,7,10,11-hexakis(hexyloxy)triphenylene (HAT6) and TNF. Nuclear magnetic resonance (NMR) line widths and cross-polarization rates are consistent with the picosecond time scale anisotropic thermal motions of the HAT6 and TNF molecules previously observed. By computational integration of Rietveld refinement analyses of neutron diffraction patterns with density experiments and short-range structural constraints from heteronuclear 2D NMR, we determine that the TNF molecules are vertically oriented between HAT6 columns. The data provide the insight that a morphology of separate hole conducting channels of HAT6 molecules can be realized in the liquid crystalline CT complex.

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Section: ■ Resultsmentioning

confidence: 94%

On the Morphology of a Discotic Liquid Crystalline Charge Transfer Complex

et al. 2012

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“…13 For HAT6, the twist angle of 37°we found will reduce J to about 50% compared to the optimal angle of 0°, as estimated from previous DFT calculations. 28 However, this typical twist angle does not account for a lower mobility of HAT6 compared to HBC-C12. The twist angle of about 30°f ound for HBC-C12 22 even leads to a smaller value of the transfer integral in comparison with HAT6 at 37°at a similar coreÀcore separation.…”

Section: ' Discussionmentioning

confidence: 99%

“…Moreover, they are comparable to the typical twist angle for HAT5 derived from molecular dynamics 31 and close to the minimum-energy twist angle of 30°as calculated with DFT. 28 The initial TWIST25 configuration with two columns set at 25°is closer to the equilibrium twist angle, which results in a sharper distribution. The TWIST60 distribution is broader, with a small additional peak at 60°originating from about 17% of the molecules that were not able to rotate during the relaxation.…”

Section: Comparison Of MD Simulations With Neutron Diffractionmentioning

confidence: 99%

Conformation, Defects, and Dynamics of a Discotic Liquid Crystal and Their Influence on Charge Transport

et al. 2011

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Future applications of discotic liquid crystals (DLCs) in electronic devices depend on a marked improvement of their conductivity properties. We present a study of 2,3,6,7,10,11-hexakishexyloxytriphenylene (HAT6) and show how local conformation, structural defects, and thermal motions on the picosecond time scale strongly affect the efficient charge transport in DLCs. A direct and successful comparison of classical molecular dynamics (MD) simulations with both neutron powder diffraction and quasielastic neutron scattering (QENS) give a full insight into the structural and dynamical properties of HAT6. The local conformation of HAT6 molecules is characterized by a mutual rotation (twist) angle of about 37° and typically a mutual aromatic-core distance of 3.4 Å instead of the average distance of 3.65 Å usually quoted. We show that a considerable number of structural traps is present in HAT6, which persist at the picosecond time scale. We find that the high disorder in the mutual positions of the aromatic cores is an important factor contributing to the limited conductivity of HAT6 compared to larger DLCs.

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“…[55][56][57][58][59] For HAT6 it is well established that the HOMO is located on the aromatic core. 60,61 Based on these considerations, we propose that the lowest excited state in HAT6-TNF forming the lower energy region of the excited CT-band is predominantly a π -π * type transition involving the highest occupied molecular orbitals (HOMO, HOMO-1, etc.) of HAT6 and the lowest unoccupied molecular orbitals from TNF (LUMO, LUMO+1, etc), 31(b) with a prominent role of the TNF nitro groups.…”

Section: B Raman Spectroscopymentioning

confidence: 99%

Electronic and vibronic properties of a discotic liquid-crystal and its charge transfer complex

Haverkate

Zbiri

Johnson

et al. 2014

The Journal of Chemical Physics

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Discotic liquid crystalline (DLC) charge transfer (CT) complexes combine visible light absorption and rapid charge transfer characteristics, being favorable properties for photovoltaic (PV) applications. We present a detailed study of the electronic and vibrational properties of the prototypic 1:1 mixture of discotic 2,3,6,7,10,11-hexakishexyloxytriphenylene (HAT6) and 2,4,7-trinitro-9-fluorenone (TNF). It is shown that intermolecular charge transfer occurs in the ground state of the complex: a charge delocalization of about 10 −2 electron from the HAT6 core to TNF is deduced from both Raman and our previous NMR measurements (2012)], implying the presence of permanent dipoles at the donor-acceptor interface. A combined analysis of density functional theory calculations, resonant Raman and UV-VIS absorption measurements indicate that fast relaxation occurs in the UV region due to intramolecular vibronic coupling of HAT6 quinoidal modes with lower lying electronic states. Relatively slower relaxation in the visible region the excited CT-band of the complex is also indicated, which likely involves motions of the TNF nitro groups. The fast quinoidal relaxation process in the hot UV band of HAT6 relates to pseudo-Jahn-Teller interactions in a single benzene unit, suggesting that the underlying vibronic coupling mechanism can be generic for polyaromatic hydrocarbons. Both the presence of ground state CT dipoles and relatively slow relaxation processes in the excited CT band can be relevant concerning the design of DLC based organic PV systems.

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Density functional calculations of potential energy surface and charge transfer integrals in molecular triphenylene derivative HAT6

Cited by 10 publications

References 43 publications

On the Morphology of a Discotic Liquid Crystalline Charge Transfer Complex

On the Morphology of a Discotic Liquid Crystalline Charge Transfer Complex

Conformation, Defects, and Dynamics of a Discotic Liquid Crystal and Their Influence on Charge Transport

Electronic and vibronic properties of a discotic liquid-crystal and its charge transfer complex

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