Synthesis and electronic properties of iso-alkyl substituted hexa-peri-hexabenzocoronenes (HBC’s) from a versatile new HBC synthon, hexakis(4-acetylphenyl)benzene

Chebny, Vincent J.; Gwengo, Chengeto; Gardinier, James R.; Rathore, Rajendra

doi:10.1016/j.tetlet.2008.06.005

Cited by 20 publications

(32 citation statements)

References 15 publications

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“…10 Typically, when electron-rich aromatics stack cofacially, the atoms are offset from each another. 24,25 The important finding here is that the thiophene units yield a more flexible structure relative to the parent c-HBC and that these contorted heterocyclic aromatics accommodate a wide range of electron acceptors within devices (vide infra). 10,22,26,27 Expanded Aromatic Cores c-HBC and c-DBTTC have similar optical and electronic properties.…”

Section: Contorted Hexabenzocoronenementioning

confidence: 94%

Contorted Polycyclic Aromatics

et al. 2014

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CONSPECTUS: This Account describes a body of research in the design, synthesis, and assembly of molecular materials made from strained polycyclic aromatic molecules. The strain in the molecular subunits severely distorts the aromatic molecules away from planarity. We coined the term "contorted aromatics" to describe this class of molecules. Using these molecules, we demonstrate that the curved pi-surfaces are useful as subunits to make self-assembled electronic materials. We have created and continue to study two broad classes of these "contorted aromatics": discs and ribbons. The figure that accompanies this conspectus displays the three-dimensional surfaces of a selection of these "contorted aromatics". The disc-shaped contorted molecules have well-defined conformations that create concave pi-surfaces. When these disc-shaped molecules are substituted with hydrocarbon side chains, they self-assemble into columnar superstructures. Depending on the hydrocarbon substitution, they form either liquid crystalline films or macroscopic cables. In both cases, the columnar structures are photoconductive and form p-type, hole- transporting materials in field effect transistor devices. This columnar motif is robust, allowing us to form monolayers of these columns attached to the surface of dielectrics such as silicon oxide. We use ultrathin point contacts made from individual single-walled carbon nanotubes that are separated by a few nanometers to probe the electronic properties of short stacks of a few contorted discs. We find that these materials have high mobility and can sense electron-deficient aromatic molecules. The concave surfaces of these disc-shaped contorted molecules form ideal receptors for the molecular recognition and assembly with spherical molecules such as fullerenes. These interfaces resemble ball-and-socket joints, where the fullerene nests itself in the concave surface of the contorted disc. The tightness of the binding between the two partners can be increased by creating more hemispherically shaped contorted molecules. Given the electronic structure of these contorted discs and the fullerenes, this junction is a molecular version of a p-n junction. These ball-and-socket interfaces are ideal for photoinduced charge separation. Photovoltaic devices containing these molecular recognition elements demonstrate approximately two orders of magnitude increase in charge separation. The ribbon-shaped, contorted molecules can be conceptualized as ultranarrow pieces of graphene. The contortion causes them to wind into helical ribbons. These ribbons can be formed into the active layer of field effect transistors. We substitute the ribbons with di-imides and therefore are able to transport electrons. Furthermore, these materials absorb light strongly and have ideal energetic alignment of their orbitals with conventional p-type electronic polymers. In solar cells, these contorted ribbons with commercial donor polymers have record efficiencies for non-fullerene-based solar cells. An area of interest for future explo...

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Section: Contorted Hexabenzocoronenementioning

confidence: 94%

Contorted Polycyclic Aromatics

et al. 2014

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“…In contrast, tBu HBC exhibits asingle oxidation wave at 0.64 V vs.Fc/Fc + in CH 2 Cl 2 (Supporting Information, Figure S4). [6,17] Moreover,t he expansion of the size of the graphitic core in FHBC results in as ignificant lowering of the first oxidation potential (by about 240 mV) in comparison to tBu HBC.…”

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confidence: 99%

“…At higher concentrations, tBu HBC shows abroad excimeric emission (at about 560 nm) indicating aggregate (that is,dimer,and higher oligomers) formation. [17] In contrast, the emission spectrum of FHBC does not show the appearance of anew excimeric band (Supporting Information, Figure S9).…”

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confidence: 99%

“…This is distinct from the solutionphase NMR spectra of other HBCs,w hich generally show broad signals owing to extensive aggregation. [7,8] TheU V/Vis absorption spectrum of FHBC is compared with well-known tBu HBC [6,17] in CH 2 Cl 2 in Figure 3A.E ach shows characteristic well-resolved vibronic structure;h owever, the significant expansion of the graphitic core in FHBC,leads to alarge red-shift (by about 90 nm) of its absorption bands (325, 451, and 486 nm; e 451 = 6.0 10 5 Lmol À1 cm À1 )and increased molar absorptivity compared to tBu HBC (230, 360, and 390 nm; e 360 = 1.9 10 5 Lmol À1 cm À1 ). Normalized emission spectra of FHBC and tBu HBC,a tt he same concentrations,F igure 3B,s how ar ed-shift of the emission bands of FHBC (582, 612 nm) compared to tBu HBC (486, 520 nm).…”

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confidence: 99%

“…Expansion of the chromophoric size of FHBC + C (l max = 460, 528, 664, 1261, and 1418 nm, e 1418 = 36 000 Lmol cm À1 )l eads to an increased molar absorptivity (by af actor of about 6) when compared to tBu HBC + C (l max = 550, 836, 1570, 1740, 2100 nm, e 2100 = 5700 Lmol À1 cm À1 ;S upporting Information, Figure S7). [6,17] Summarizing,w hile tBu HBC forms aggregates in neutral, excited, and radical cation states,a sj udged by,r espectively, broad NMR spectra, observation of excimeric emission (at about 560 nm), [6,17] and observation of intervalence transition (at 1200 nm) [6,17] in its radical cation spectrum in the presence of neutral tBu HBC ( Supporting Information, Figures S8,S9), such spectroscopic signatures of aggregation were completely absent in the case of FHBC.Acursory examination of the molecular structures of FHBC and tBu HBC suggests that the narrow bay areas in FHBC do not afford arrangement of two hexyl chains in as taggered (sandwich-like) dimer.O nt he other hand, the relatively wider bay areas in tBu HBC provide sufficient space for smaller methyl groups to be accommodated in as andwich-like (staggered) dimeric structure (Figure 5A).…”

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confidence: 99%

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FHBC, a Hexa‐peri‐hexabenzocoronene–Fluorene Hybrid: A Platform for Highly Soluble, Easily Functionalizable HBCs with an Expanded Graphitic Core

et al. 2017

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Materials based upon hexa-peri-hexabenzocoronenes (HBCs) show significant promise in a variety of photovoltaic applications. There remains the need, however, for a soluble, versatile, HBC-based platform, which can be tailored by incorporation of electroactive groups or groups that can prompt self-assembly. The synthesis of a HBC-fluorene hybrid is presented that contains an expanded graphitic core that is highly soluble, resists aggregation, and can be readily functionalized at its vertices. This new HBC platform can be tailored to incorporate six electroactive groups at its vertices, as exemplified by a facile synthesis of a representative hexaaryl derivative of FHBC. Synthesis of new FHBC derivatives, containing electroactive functional groups that can allow controlled self-assembly, may serve as potential long-range charge-transfer materials for photovoltaic applications.

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Robust Aromatic Cation Radicals as Redox Tunable Oxidants

Talipov

Rathore

2015

Organic Redox Systems

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Synthesis and electronic properties of iso-alkyl substituted hexa-peri-hexabenzocoronenes (HBC’s) from a versatile new HBC synthon, hexakis(4-acetylphenyl)benzene

Cited by 20 publications

References 15 publications

Contorted Polycyclic Aromatics

Contorted Polycyclic Aromatics

FHBC, a Hexa‐peri‐hexabenzocoronene–Fluorene Hybrid: A Platform for Highly Soluble, Easily Functionalizable HBCs with an Expanded Graphitic Core

Robust Aromatic Cation Radicals as Redox Tunable Oxidants

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