Discotic liquid crystals: a new generation of organic semiconductors

Sergeyev, Sergey; Pisula, Wojciech; Geerts, Yves

doi:10.1039/b417320c

Cited by 1,340 publications

(873 citation statements)

References 234 publications

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“…[1][2][3] Although electron mobility remains a challenge, these represent lightweight, flexible alternatives that are more readily processed using solution-based methods. Within this arena, the opportunities proffered by the exceptional electronic and physical properties of graphene and its derivatives are undeniable.…”

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confidence: 99%

Methoxy functionalisation: exerting synthetic control of the supramolecular and electronic structure of nitrogen-doped nanographenes

et al. 2014

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We describe a series of functionalized N-containing heterosuperbenzenes, created with a view to investigating the strategic role of methoxy substituents in (i) promoting cyclodehydrogenation and (ii) tuning the electronic properties and (iii) the supramolecular order in the resultant fused products.The dominance of inorganic semiconductors in the manufacture of optoelectronic devices and field effect transistors is gradually being undermined by the emergence of functional organic materials. [1][2][3] Although electron mobility remains a challenge, these represent lightweight, flexible alternatives that are more readily processed using solution-based methods. Within this arena, the opportunities proffered by the exceptional electronic and physical properties of graphene and its derivatives are undeniable. [4][5][6] As many aspects in the formation of large graphitic sheets are difficult to control, synthetic chemists have pioneered routes to nanographenes with impressive and varying dimensions, and an array of peripheral substituents. 7-10 Dependent on the latter are a range of material characteristics e.g. the nature of the p-p interactions, HOMO-LUMO gaps and film-forming capabilities. [11][12][13][14] The ability to manufacture graphene systems to such specificity is notably absent in exfoliation 15 /epitaxial growth 16 processes, and this makes the further development of bottom-up synthetic methodologies for the formation of next-generation and heteroatomcontaining graphenes all the more important. 10,17 Oxidative cyclodehydrogenation is a key step in the chemical formation of planarised ring systems. All-carbon systems cyclise rapidly, while heteroatom-containing polyphenylenes appear to adopt a more complex mechanism for ring closure, e.g. both partially and fully fused species tend to be generated in a single reaction. [18][19][20] Electron donating substituents both direct and promote CC bond formation under cyclodehydrogenation conditions. 21,22 Tuning the intramolecular properties of graphenes is one step in the search for technology-enabling materials. Also essential is the ability to exert some supramolecular control of structure. Disc-like molecules tend to aggregate in columnar p-p stacks which can be either enhanced or perturbed by peripheral units e.g. long chain alkyl substituted hexaperihexabenzocoronenes frequently exhibit liquid crystalline behaviour, 2 whereas their iodo-or tert-butyl-functionalised derivatives give rise to Bernal-stacked crystalline dimers. 23 This work reveals how the combination of heteroatom doping (as pioneered by Draper et al.), 17,24-26 with H-bonding peripheral substituents, can unlock some exciting new applications for nanographene materials by controlling the outcome of the synthetic process and the HOMO-LUMO gaps and intermolecular order of the end-products.The synthetic methods used to form the precursor polyphenylenes were modifications of published routes involving cyclopentadienones (generated via two-fold Knoevenagel condensations) and their subsequent [2+4] D...

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confidence: 99%

Methoxy functionalisation: exerting synthetic control of the supramolecular and electronic structure of nitrogen-doped nanographenes

et al. 2014

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“…TP-TNI derivative containing linear C 12 H 25 side chains, named as TP-TNI-C12, was synthesized by the condensation reaction between hexaaminotriphenylene and the corresponding monoanhydride bearing a n-dodecyl chain. 12 TP-TNI-C12 was obtained as an inseparable statistic mixture of cis-(symmetric) and trans-(asymmetric) isomers with a ratio of 1:3, both having good solubility in solvents such as CH 2 Figure S2). UV-vis spectroscopic studies of the TP-TNI-C12 solution indicated a broad lowest frequency absorption peak spanning 430 and 710 nm, with a peak centered at 515 nm (ε = 23900 M -1 cm -1 ) and a shoulder peak at 607 nm (ε = 12100 M -1 cm -1 ).…”

Section: Resultsmentioning

confidence: 99%

“…[1][2][3] The strong intermolecular interactions between the large planar aromatic surfaces incur favorable tendency for such molecules to stack into one-dimensional (1D) columns, which can serve as the preferred charge carrier transporting pathway through inter-stack hopping. In the solid state, these 1D columns can further organize into two dimensional suprastructures.…”

Section: Introductionmentioning

confidence: 99%

Understanding Electron Transport in Disk-Shaped Triphenylene-Tris(naphthaleneimidazole)s through Structural Modification and Theoretical Investigation

Zhang

Hanifi

Fernández‐Liencres

et al. 2017

ACS Appl. Mater. Interfaces

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ABSTRACT. Disk-shaped molecules with large aromatic π-surface are a class of organic semiconductors of which the charge carrier transport properties could be greatly facilitated by preferred intermolecular stacking of the π-surfaces. The optical and electronic properties are not only determined by the core aromatic structure of these disk-shaped molecules, but also strongly dependent on the sidechains, which directly impact the molecular self-assembly behavior in condensed phases. Triphenylene-tris(naphthaleneimidazole) (TP-TNI) is a recently reported ntype semiconductor featuring a large π-core and branched sidechains with an electron transporting mobility reaching 10 -4 cm 2 V -1 s -1 . In order to further improve material performance, a detailed study is needed to understand the dependence of carrier transporting properties on both the core electronic structure and the sidechain. Here we present the detailed synthesis and characterization of a TP-TNI derivative bearing linear sidechains, which has demonstrated a field effect electron transport mobility up to 1.3×10 -3 cm 2 V -1 s -1 . The more than one order improvement of electron transport properties over the branched side chain homologue can be correlated to ordered twisted packing in the thin film, as revealed by in situ variable temperature grazing incidence wide-angle X-ray scattering (GIWAXS) studies. In-depth theoretical understanding of the frontier orbitals, reorganization energies and charge transfer integrals of TP-TNI molecules have provided further insight into the relationship between molecular stacking geometry and charge transporting properties.3

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“…In the arrangements of such discotic liquid crystals, again coplanar motifs are frequently found. 12 The initial HBC molecules form a flat-lying monolayer, which due to the lattice matching of the molecular carbon frame and the HOPG substrate also results in a laterally well-defined seed layer. This slight constraint compared to free nucleation (as, e.g., in crystal growth) results in nucleation in the energetically nearly equivalent coplanar polymorph.…”

Section: Discussionmentioning

confidence: 99%

Lattice Matching as the Determining Factor for Molecular Tilt and Multilayer Growth Mode of the Nanographene Hexa-peri-hexabenzocoronene

Beyer

Breuer

Ndiaye

et al. 2014

ACS Appl. Mater. Interfaces

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ABSTRACT:The microstructure, morphology, and growth dynamics of hexa-peri-hexabenzocoronene (HBC, C 42 H 18 ) thin films deposited on inert substrates of similar surface energies are studied with particular emphasis on the influence of substrate symmetry and substrate−molecule lattice matching on the resulting films of this material. By combining atomic force microscopy (AFM) with X-ray diffraction (XRD), X-ray absorption spectroscopy (NEXAFS), and in situ X-ray reflectivity (XRR) measurements, it is shown that HBC forms polycrystalline films on SiO 2 , where molecules are oriented in an upright fashion and adopt the known bulk structure. Remarkably, HBC films deposited on highly oriented pyrolytic graphite (HOPG) exhibit a new, substrate-induced polymorph, where all molecules adopt a recumbent orientation with planar π-stacking. Formation of this new phase, however, depends critically on the coherence of the underlying graphite lattice since HBC grown on defective HOPG reveals the same orientation and phase as on SiO 2 . These results therefore demonstrate that the resulting film structure and morphology are not solely governed by the adsorption energy but also by the presence or absence of symmetry-and lattice-matching between the substrate and admolecules. Moreover, it highlights that weakly interacting substrates of high quality and coherence can be useful to induce new polymorphs with distinctly different molecular arrangements than the bulk structure.

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Discotic liquid crystals: a new generation of organic semiconductors

Cited by 1,340 publications

References 234 publications

Methoxy functionalisation: exerting synthetic control of the supramolecular and electronic structure of nitrogen-doped nanographenes

Methoxy functionalisation: exerting synthetic control of the supramolecular and electronic structure of nitrogen-doped nanographenes

Understanding Electron Transport in Disk-Shaped Triphenylene-Tris(naphthaleneimidazole)s through Structural Modification and Theoretical Investigation

Lattice Matching as the Determining Factor for Molecular Tilt and Multilayer Growth Mode of the Nanographene Hexa-peri-hexabenzocoronene

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