Bridging the Gap between Pentacene and Perfluoropentacene: Synthesis and Characterization of 2,3,9,10-Tetrafluoropentacene in the Neutral, Cationic, and Dicationic States

Shen, Bin; Geiger, Thomas; Einholz, Ralf; Reicherter, Florian; Schundelmeier, Simon; Maichle‐Mößmer, Cäcilia; Speiser, Bernd; Bettinger, Holger F.

doi:10.1021/acs.joc.7b03241

Cited by 25 publications

(47 citation statements)

References 91 publications

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“…The C−F bond lengths range between 1.36 and 1.37 Å in 10 , whereas the C−F bond lengths in 11 are shorter (1.34–1.36 Å). These values are similar to the ones found in 12 and PFP . The closest intermolecular F−F contacts in the crystal packing of 10 have a distance of 3.34 Å.…”

Section: Resultssupporting

confidence: 85%

“…[c] Calculated at the M06/6‐31G* level of theory. [d] Values differ slightly from the previous measurement and are based on additional data for conditions given in footnote [a]. [e] ox E 1/2 and red E 1/2 in 0.1 m n Bu 4 PF 6 /CH 2 Cl 2 .…”

Section: Resultsmentioning

confidence: 92%

“…The α bands follow the same trend, but the shift is smaller. The Stokes shift increases from 189 cm −1 in 12 to 327 ( 10 ) and 334 cm −1 ( 11 ), respectively.…”

Section: Resultsmentioning

confidence: 96%

“…The electrochemical redox processes associated with 12 have already been described recently, and are briefly summarized here. The radical cation and anion, as the one‐electron oxidation and reduction products of 12 , are generated in a reversible or quasi‐reversible electron transfer, respectively, at a Pt electrode in 1,2‐dichlorobenzene.…”

Section: Resultsmentioning

confidence: 99%

“…In contrast, no 13 C{ 1 H} NMR spectra could be obtained, even at 120 °C in [D 2 ]tetrachloroethane as done previously for NMR characterization of 12 . Although 12 is stable at this temperature for an extended period of time, and was indeed crystallized by slow cooling of a hot 1,2,4‐trichlorobenzene solution, isomer 10 underwent a reaction. After 3 h of heating to 120 °C, all pentacene 1 H NMR signals had completely disappeared (Figure ) and a new set of three signals (integration ratio 8:8:4) had formed, indicative of a single reaction product with the same symmetry.…”

Section: Resultsmentioning

confidence: 99%

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Modulating the Electronic and Solid‐State Structure of Organic Semiconductors by Site‐Specific Substitution: The Case of Tetrafluoropentacenes

Geiger

Schundelmeier

Hummel

et al. 2020

Chemistry A European J

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The properties as well as solid‐state structures, singlet fission, and organic field‐effect transistor (OFET) performance of three tetrafluoropentacenes (1,4,8,11: 10, 1,4,9,10: 11, 2,3,9,10: 12) are compared herein. The novel compounds 10 and 11 were synthesized in high purity from the corresponding 6,13‐etheno‐bridged precursors by reaction with dimethyl 1,2,4,5‐tetrazine‐3,6‐dicarboxylate at elevated temperatures. Although most of the molecular properties of the compounds are similar, their chemical reactivity and crystal structures differ considerably. Isomer 10 undergoes the orbital symmetry forbidden thermal [4+4] dimerization, whereas 11 and 12 are much less reactive. The isomers 11 and 12 crystallize in a herringbone motif, but 10 prefers π–π stacking. Although the energy of the first electric dipole‐allowed optical transition varies only within 370 cm−1 (0.05 eV) for the neutral compounds, this amounts to roughly 1600 cm−1 (0.20 eV) for radical cations and 1300 cm−1 (0.16 eV) for dications. Transient spectroscopy of films of 11 and 12 reveals singlet‐fission time constants (91±11, 73±3 fs, respectively) that are shorter than for pentacene (112±9 fs). OFET devices constructed from 11 and 12 show close to ideal thin‐film transistor (TFT) characteristics with electron mobilities of 2×10−3 and 6×10−2 cm2 V−1 s−1, respectively.

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Section: Resultssupporting

confidence: 85%

Section: Resultsmentioning

confidence: 92%

“…The α bands follow the same trend, but the shift is smaller. The Stokes shift increases from 189 cm −1 in 12 to 327 ( 10 ) and 334 cm −1 ( 11 ), respectively.…”

Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Modulating the Electronic and Solid‐State Structure of Organic Semiconductors by Site‐Specific Substitution: The Case of Tetrafluoropentacenes

Geiger

Schundelmeier

Hummel

et al. 2020

Chemistry A European J

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Energy Level Engineering in Organic Thin Films by Tailored Halogenation

Ortstein

Hutsch

Hinderhofer

et al. 2020

Adv Funct Materials

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In modern electronics, it is essential to adapt band structures by adjusting energy levels and band gaps. At first sight, this “band structure engineering” seems impossible in organic semiconductors, which usually exhibit localized electronic states instead of Bloch bands. However, the strong Coulomb interaction in organic semiconductors allows for a continuous shift of the ionization energy (IE) over a wide range by mixing molecules with halogenated derivatives that exhibit different quadrupole moments. Here, this effect of energy level engineering on blends of pentacene and two fluorinated derivatives, in which the position but not the number of fluorine atoms differ, is studied. Structural investigations confirm that pentacene forms intermixed phases in blends with the fluorinated species. The investigation of electronic properties and simulations reveals a much larger shift of the ionization energy (1.5 eV) than in previous studies, allowing to test this model in a range not investigated so far, and emphasizing the role of the position of the halogen atoms. The tuning effect is preserved in electronic devices such as field‐effect transistors and significantly influences device characteristics.

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Dipolar Substitution Impacts Growth and Electronic Properties of Para‐Sexiphenyl Thin Films

Aghdassi

Bhagat

et al. 2019

Adv Materials Inter

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material class over their inorganic counterparts. [1] For both OSCs based on conjugated organic molecules and conjugated polymers this is often done by modifying the peripheral substitution pattern of a given parent compound. [1,2] This can significantly alter its electronic properties, particularly those of thin films through collective electrostatic effects. [3][4][5] The energies of the OSC frontier molecular orbital levels and their energy-level alignment at heterointerfaces both with other OSCs and conductive electrodes play a crucial role in device applications. [6,7] This is mainly because interface properties define charge-injection barriers in light-emitting diodes or promote exciton dissociation in solar cells. As shown in several studies, adding strong intramolecular polar bonds, such as CF, to the parent compound allows changing the ionization energy (IE) of ordered molecular assemblies substantially, [8,9] e.g., from 4.80 eV for pentacene (PEN) to 6.65 eV for perfluoropentacene [8] in thin films grown on native silicon oxide (SiO x ). Notably, via partial fluorination of the compound this dramatic effect can be deliberately tuned. [7,10] In general, partial nonsymmetric fluorination allows introducing a net molecular It is shown that fluorination of para-sexiphenyl (6P) at the meta-or orthopositions of one terminal phenyl ring, as well as the addition of a terminal cyano-group has an eminent impact on both growth and electronic properties of thin films. X-ray diffraction techniques indicate that films of meta-substituted 6P (m-2F-6P) develop a smooth, layered structure showing crystalline order within the layers only. Contrary, both ortho-substituted (o-2F-6P) and cyano-substituted 6P (CN-6P) form films of 3D crystalline order. The correlation of structural information with data from ultraviolet photoelectron spectroscopy reveals that m-2F-6P and CN-6P do not show preferentially oriented dipoles in the film, while o-2F-6P grows with collective downward orientation of the dipole moments. The subtle difference in substitution position has a dramatic impact on the thin-film ionization energy, which increases from 5.40 (ortho) to 6.80 eV (meta) and reaches even 7.50 eV for CN-6P. The present study shows that nonsymmetric substitution, which induces molecular dipole moments via intramolecular polar bonds, strongly impacts structure, morphology, and electronic properties of thin films. Thusly modifying common conjugated organic materials represents a valuable tool to establish smooth, crystalline layers with altered energetics at hetero-interfaces with organic or electrode materials in electronic devices.Our ability to tailor the electronic properties of organic semiconductors (OSCs) by altering the chemical structure of the constituting molecules represents a key advantage of this

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Bridging the Gap between Pentacene and Perfluoropentacene: Synthesis and Characterization of 2,3,9,10-Tetrafluoropentacene in the Neutral, Cationic, and Dicationic States

Cited by 25 publications

References 91 publications

Modulating the Electronic and Solid‐State Structure of Organic Semiconductors by Site‐Specific Substitution: The Case of Tetrafluoropentacenes

Modulating the Electronic and Solid‐State Structure of Organic Semiconductors by Site‐Specific Substitution: The Case of Tetrafluoropentacenes

Energy Level Engineering in Organic Thin Films by Tailored Halogenation

Dipolar Substitution Impacts Growth and Electronic Properties of Para‐Sexiphenyl Thin Films

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