Structure and Dynamics of a Discotic Liquid‐Crystalline Charge‐Transfer Complex

Kruglova, Olga; Mendes, Eduardo; Yildirim, Zeynep; Wübbenhorst, Michael; Mulder, Fokko M.; Stride, John A.; Picken, Stephen J.; Kearley, Gordon J.

doi:10.1002/cphc.200700134

Cited by 31 publications

(38 citation statements)

References 37 publications

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“…We measured a skeletal density of 1.08 ± 0.01 g cm −3 for HAT6d-TNFd, corresponding to an increase in density of about 7% with respect to HAT6. 17 These observations indicate that the columnar morphology has drastically changed in the charge transfer compound. For a hexagonal columnar structure with the TNF sandwiched between the HAT6 molecules, the column−column distance should be about 17% smaller compared to pure HAT6.…”

Section: ■ Materials and Methodsmentioning

confidence: 95%

“…Liquid-like motions due to "flip-flopping" of the dihedral angles between the carbons of the HAT6 tails occur on a comparable time scale for the CT complex and for pristine HAT6. 17,31 Second, a rapid buildup of spin polarization is observed for the core 13 C H (within 0.1 ms for both HAT6 and HAT6-TNF at ambient temperature) and for the TNF C−H carbons (within 1 ms), revealing a more rigid environment than for the tails. Third, the resolution in the proton dimension (e.g., Figure 6) for all HAT6 and TNF signals is quite good for the solid state MAS data sets collected without homonuclear decoupling during t 1 ( 1 H) evolution.…”

Section: ■ Materials and Methodsmentioning

confidence: 96%

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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: ■ Materials and Methodsmentioning

confidence: 95%

Section: ■ Materials and Methodsmentioning

confidence: 96%

On the Morphology of a Discotic Liquid Crystalline Charge Transfer Complex

et al. 2012

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“…Earlier efforts through NMR [6 -13], dielectric spectroscopy (DS) [11][12][13][14][15][16][17][18], neutron scattering [19,20], and computer simulations [20 -22] have shed light on the dynamics. The NMR studies identified (i) the main process as reflecting the axial motion of the discs around the columnar axis [6,11] and (ii) quasiperiodic regions of high and low packing density along the columns [8] as proposed by de Gennes [23].…”

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confidence: 99%

Origin of the Complex Molecular Dynamics in Functionalized Discotic Liquid Crystals

et al. 2008

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The molecular dynamics of three dipole functionalized hexa-peri-hexabenzocoronenes have been studied using site-specific NMR techniques and dielectric spectroscopy as a function of temperature and pressure. These probes (i) suggest that the thermodynamic state completely controls the dynamic response, (ii) clarify the origin of two dynamic processes associated with the presence of two glass temperatures, and (iii) provide the first phase diagram for substances of this kind.

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“…23,33 The charge transfer compounds were obtained by mixing HAT6 (or HAT6D) with 2,4,7-trinitro-9-fluorenone (TNF) in a 1:1 molar proportion in dichloromethane. 23 The mixture was subsequently evaporated to dryness at room temperature. To remove any traces of solvent and to ensure the correct phase behavior, the resulting composite was heated to the isotropization temperature, T = 237…”

Section: A Sample Preparationmentioning

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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Structure and Dynamics of a Discotic Liquid‐Crystalline Charge‐Transfer Complex

Cited by 31 publications

References 37 publications

On the Morphology of a Discotic Liquid Crystalline Charge Transfer Complex

On the Morphology of a Discotic Liquid Crystalline Charge Transfer Complex

Origin of the Complex Molecular Dynamics in Functionalized Discotic Liquid Crystals

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

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