Heteroepitaxy in Organic/TMD Hybrids and Challenge to Achieve it for TMD Monolayers: The Case of Pentacene on WS2 and WSe2.

The intriguing photophysical properties of monolayer stacks of different transition-metal dichalcogenides (TMDs), revealing rich exciton physics including interfacial and moiré excitons, have recently prompted an extension of similar investigations to hybrid systems of TMDs and organic films, as the latter combine large photoabsorption cross sections with the ability to tailor energy levels by targeted synthesis. To go beyond single-molecule photoexcitations and exploit the excitonic signatures of organic solids, crystalline molecular films are required. Moreover, a defined registry on the substrate, ideally an epitaxy, is desirable to also achieve an excitonic coupling in momentum space. This poses a certain challenge as excitonic dipole moments of organic films are closely related to the molecular orientation and film structure, which critically depend on the support roughness. Using X-ray diffraction, optical polarization, and atomic force microscopy, we analyzed the structure of pentacene (PEN) multilayer films grown on WSe2(001) and WS2(001) and identified an epitaxial alignment. While (022)-oriented PEN films are formed on both substrates, their azimuthal orientations are quite different, showing an alignment of the molecular L-axis along the ⟨110⟩WSe2 and ⟨100⟩WS2 directions. This intrinsic epitaxial PEN growth depends, however, sensitively on the substrates surface quality. While it occurs on exfoliated TMD single crystals and multilayer flakes, it is hardly found on exfoliated monolayers, which often exhibit bubbles and wrinkles. This enhances the surface roughness and results in (001)-oriented PEN films with upright molecular orientation but without any azimuthal alignment. However, monolayer flakes can be smoothed by AFM operated in contact mode or by transferring to ultrasmooth substrates such as hBN, which again yields epitaxial PEN films. As different PEN orientations result in different characteristic film morphologies (elongated mesa islands vs pyramidal dendrites), which can be easily distinguished by AFM or optical microscopy, this provides a simple means to judge the roughness of the used TMD surface.

Cluster-Based Approach Utilizing Optimally Tuned TD-DFT to Calculate Absorption Spectra of Organic Semiconductor Thin Films.

The photophysics of organic semiconductor (OSC) thin films or crystals has garnered significant attention in recent years since a comprehensive theoretical understanding of the various processes occurring upon photoexcitation is crucial for assessing the efficiency of OSC materials. To date, research in this area has relied on methods using Frenkel-Holstein Hamiltonians, calculations of the GW-Bethe-Salpeter equation with periodic boundaries, or cluster-based approaches using quantum chemical methods, with each of the three approaches having distinct advantages and disadvantages. In this work, we introduce an optimally tuned, range-separated time-dependent density functional theory approach to accurately reproduce the total and polarization-resolved absorption spectra of pentacene, tetracene, and perylene thin films, all representative OSC materials. Our approach achieves excellent agreement with experimental data (mostly ≤0.1 eV) when combined with the utilization of clusters comprising multiple monomers and a standard polarizable continuum model to simulate the thin-film environment. Our protocol therefore addresses a major drawback of cluster-based approaches and makes them attractive tools for OSC investigations. Its key advantages include its independence from external, system-specific fitting parameters and its straightforward application with well-known quantum chemical program codes. It demonstrates how chemical intuition can help to reduce computational cost and still arrive at chemically meaningful and almost quantitative results.

Chemical Doping by Fluorination and Its Impact on All Energy Levels of π-Conjugated Systems.

Halogenation of organic molecules causes chemical shifts of C1s core-level binding energies that are commonly used as fingerprints to identify chemical species. Here, we use synchrotron-based X-ray photoelectron spectroscopy and density functional theory calculations to unravel such chemical shifts by examining different partially fluorinated pentacene derivatives. Core-level shifts occur even for carbon atoms distant from the fluorination positions, yielding a continuous shift of about 1.8 eV with increasing degree of fluorination for pentacenes. Since also their LUMO energies shift markedly with the degree of fluorination of the acenes, core-level shifts result in a nearly constant excitation energy of the leading π* resonance as obtained in complementary recorded K-edge X-ray absorption spectra, hence demonstrating that local fluorination affects the entire π-system, including valence and core levels. Our results thus challenge the common picture of characteristic chemical core-level energies as fingerprint signatures of fluorinated π-conjugated molecules.

Shape control in 2D molecular nanosheets by tuning anisotropic intermolecular interactions and assembly kinetics.

Since molecular materials often decompose upon exposure to radiation, lithographic patterning techniques established for inorganic materials are usually not applicable for the fabrication of organic nanostructures. Instead, molecular self-organisation must be utilised to achieve bottom-up growth of desired structures. Here, we demonstrate control over the mesoscopic shape of 2D molecular nanosheets without affecting their nanoscopic molecular packing motif, using molecules that do not form lateral covalent bonds. We show that anisotropic attractive Coulomb forces between partially fluorinated pentacenes lead to the growth of distinctly elongated nanosheets and that the direction of elongation differs between nanosheets that were grown and ones that were fabricated by partial desorption of a complete molecular monolayer. Using kinetic Monte Carlo simulations, we show that lateral intermolecular interactions alone are sufficient to rationalise the different kinetics of structure formation during nanosheet growth and desorption, without inclusion of interactions between the molecules and the supporting MoS2 substrate. By comparison of the behaviour of differently fluorinated molecules, experimentally and computationally, we can identify properties of molecules with regard to interactions and molecular packing motifs that are required for an effective utilisation of the observed effect.

F-Center-Mediated Growth of Patterned Organic Semiconductor Films on Alkali Halides.

Organic semiconductors combine flexible tailoring of their optoelectronic properties by synthetic means with strong light-matter coupling, which is advantageous for organic electronic device applications. Although spatially selective deposition has been demonstrated, lateral patterning of organic films with simultaneous control of molecular and crystalline orientation is lacking as traditional lithography is not applicable. Here, a new patterning approach based on surface-localized F-centers (halide vacancies) generated by electron irradiation of alkali halides is presented, which allows structural control of molecular adlayers. Combining optical and atomic force microscopy, X-ray diffraction, and density functional theory (DFT) calculations, it is shown that dinaphthothienothiophene (DNTT) molecules adopt an upright orientation on pristine KCl surfaces, while the F-centers stabilize a recumbent orientation, and that these orientations are maintained in thicker films. This specific nucleation results also in different crystallographic morphologies, namely, densely packed islands and jagged fibers, each epitaxially aligned on the KCl surface. Spatially selective surface irradiation can also be used to create patterns of F-centers and thus laterally patterned DNTT films, which can be further transferred to any (including elastomer) substrate due to the water solubility of the alkali halide growth templates.

Novel Poxin Stable cGAMP-Derivatives Are Remarkable STING Agonists.

2',3'-cGAMP is a cyclic A- and G-containing dinucleotide second messenger, which is formed upon cellular recognition of foreign cytosolic DNA as part of the innate immune response. The molecule binds to the adaptor protein STING, which induces an immune response characterized by the production of type I interferons and cytokines. The development of STING-binding molecules with both agonistic as well as antagonistic properties is currently of tremendous interest to induce or enhance antitumor or antiviral immunity on the one hand, or to treat autoimmune diseases on the other hand. To escape the host innate immune recognition, some viruses encode poxin endonucleases that cleave 2',3'-cGAMP. Here we report that dideoxy-2',3'-cGAMP (1) and analogs thereof, which lack the secondary ribose-OH groups, form a group of poxin-stable STING agonists. Despite their reduced affinity to STING, particularly the compound constructed from two A nucleosides, dideoxy-2',3'-cAAMP (2), features an unusually high antitumor response in mice.

Template and Temperature-Controlled Polymorph Formation in Squaraine Thin Films.

Controlling the polymorph formation in organic semiconductor thin films by the choice of processing parameters is a key factor for targeted device performance. Small molecular semiconductors such as the prototypical anilino squaraine compound with branched butyl chains as terminal functionalization (SQIB) allow both solution and vapor phase deposition methods. SQIB has been considered for various photovoltaic applications mainly as amorphous isotropic thin films due to its broad absorption within the visible to deep-red spectral range. The two known crystalline polymorphs adopting a monoclinic and orthorhombic crystal phase show characteristic Frenkel excitonic spectral signatures of overall H-type and J-type aggregates, respectively, with additional pronounced Davydov splitting. This gives a recognizable polarized optical response of crystalline thin films suitable for identification of the polymorphs. Both phases emerge with a strongly preferred out-of-plane and rather random in-plane orientation in spin-casted thin films depending on subsequent thermal annealing. By contrast, upon vapor deposition on dielectric and conductive substrates, such as silicon dioxide, potassium chloride, graphene, and gold, the polymorph expression depends basically on the choice of growth substrate. The same pronounced out-of-plane orientation is adopted in all crystalline cases, but with a surface templated in-plane alignment in case of crystalline substrates. Strikingly, the amorphous isotropic thin films obtained by vapor deposition cannot be crystallized by thermal postannealing, which is a key feature for the spin-casted thin films, here monitored by polarized in situ microscopy. Combining X-ray diffraction, atomic force microscopy, ellipsometry, and polarized spectro-microscopy, we identify the processing-dependent evolution of the crystal phases, correlating morphology and molecular orientations within the textured SQIB films.

Chemical Synthesis of the Fluorescent, Cyclic Dinucleotides cth GAMP.

The cGAS-STING pathway is known for its role in sensing cytosolic DNA introduced by a viral infection, bacterial invasion or tumorigenesis. Free DNA is recognized by the cyclic GMP-AMP synthase (cGAS) catalyzing the production of 2',3'-cyclic guanosine monophosphate-adenosine monophosphate (2',3'-cGAMP) in mammals. This cyclic dinucleotide acts as a second messenger, activating the stimulator of interferon genes (STING) that finally triggers the transcription of interferon genes and inflammatory cytokines. Due to the therapeutic potential of this pathway, both the production and the detection of cGAMP via fluorescent moieties for assay development is of great importance. Here, we introduce the paralleled synthetic access to the intrinsically fluorescent, cyclic dinucleotides 2'3'-cth GAMP and 3'3'-cth GAMP based on phosphoramidite and phosphate chemistry, adaptable for large scale synthesis. We examine their binding properties to murine and human STING and confirm biological activity including interferon induction by 2'3'-cth GAMP in THP-1 monocytes. Two-photon imaging revealed successful cellular uptake of 2'3'-cth GAMP in THP-1 cells.

Regioselective Fluorination of Acenes: Tailoring of Molecular Electronic Levels and Solid-State Properties.

Optoelectronic properties of molecular solids are important for organic electronic devices and are largely determined by the adopted molecular packing motifs. In this study, we analyzed such structure-property relationships for the partially regioselective fluorinated tetracenes 1,2,12-trifluorotetracene, 1,2,10,12-tetrafluorotetracene and 1,2,9,10,11-pentafluorotetracene that were further compared with tetracene and perfluoro-tetracene. Quantum chemical DFT calculations in combination with optical absorption spectroscopy data show that the frontier orbital energies are lowered with the degree of fluorination, while their optical gap is barely affected. However, the crystal structure changes from a herringbone packing motif of tetracene towards a planar stacking motif of the fluorinated tetracene derivatives, which is accompanied by the formation of excimers and leads to strongly red-shifted photoluminescence with larger lifetimes.

Polarization Resolved Optical Excitation of Charge-Transfer Excitons in PEN:PFP Cocrystalline Films: Limits of Nonperiodic Modeling.

Charge-transfer excitons (CTXs) at organic donor/acceptor interfaces are considered important intermediates for charge separation in photovoltaic devices. Crystalline model systems provide microscopic insights into the nature of such states as they enable microscopic structure-property investigations. Here, we use angular-resolved UV/vis absorption spectroscopy to characterize the CTXs of crystalline pentacene:perfluoro-pentacene (PEN:PFP) films allowing determination of the polarization of this state. This analysis is complemented by first-principles many-body calculations, performed on the three-dimensional PEN:PFP cocrystal, which confirm that the lowest-energy excitation is a CTX. Analogous simulations performed on bimolecular clusters are unable to reproduce this state. We ascribe this failure to the lack of long-range interactions and wave function periodicity in these cluster calculations, which appear to remain a valid tool for modeling properties of organic materials ruled by local intermolecular couplings.

Temperature-programmed desorption of large molecules: influence of thin film structure and origin of intermolecular repulsion.

Although the exact knowledge of the binding energy of organic adsorbates on solid surfaces is of vital importance for the realization of molecular nanostructures and the theoretical modelling of molecule-substrate interactions, an experimental determination is by no means trivial. Temperature-programmed desorption (TPD) is a widely used technique that can provide such information, but a quantitative analysis requires detailed knowledge of the pre-exponential factor of desorption and is therefore rarely performed on a quantitative level for larger molecules that often exhibit notable mutual intermolecular interactions. Here, we provide a thorough anlysis of TPD data of monolayers of pentacene and perfluoropentacene adsorbed on Au(111) that serve as a model system for polycyclic aromatic hydrocarbons adsorbed on noble metal surfaces. We show that the pre-exponential factor varies by several orders of magnitude with the surface coverage and evolves in a step-like fashion due to the sudden activation of a rotational degree of freedom during thermally controlled monolayer desorption. Using complementary coverage-dependent work function measurements, the interface dipole moments were determined. This allows to identify the origin and quantify the relative contributions of the lateral intermolecular interactions, which we modelled by force field calculations. This analysis clearly shows that the main cause for intermolecular repulsion are electrostatic interactions between the intramolecular charge distributions, while interface dipoles play only a minor role.

BusR senses bipartite DNA binding motifs by a unique molecular ruler architecture.

The cyclic dinucleotide second messenger c-di-AMP is a major player in regulation of potassium homeostasis and osmolyte transport in a variety of bacteria. Along with various direct interactions with proteins such as potassium channels, the second messenger also specifically binds to transcription factors, thereby altering the processes in the cell on the transcriptional level. We here describe the structural and biochemical characterization of BusR from the human pathogen Streptococcus agalactiae. BusR is a member of a yet structurally uncharacterized subfamily of the GntR family of transcription factors that downregulates transcription of the genes for the BusA (OpuA) glycine-betaine transporter upon c-di-AMP binding. We report crystal structures of full-length BusR, its apo and c-di-AMP bound effector domain, as well as cryo-EM structures of BusR bound to its operator DNA. Our structural data, supported by biochemical and biophysical data, reveal that BusR utilizes a unique domain assembly with a tetrameric coiled-coil in between the binding platforms, serving as a molecular ruler to specifically recognize a 22 bp separated bipartite binding motif. Binding of c-di-AMP to BusR induces a shift in equilibrium from an inactivated towards an activated state that allows BusR to bind the target DNA, leading to transcriptional repression.

Assessment of Diadenylate Cyclase and c-di-AMP-phosphodiesterase Activities Using Thin-layer and Ion Exchange Chromatography.

All living cells use cyclic nucleotides as second messengers for signal sensing and transduction. Cyclic di-3',5'-adenosine monophosphate (c-di-AMP) is primarily involved in the control of bacterial and euryarcheal osmoadaptation and is produced by diadenylate cyclases from two molecules of ATP. Specific phosphodiesterases hydrolyze c-di-AMP to the linear phosphoadenylate adenosine 5'-pApA or to AMP. Different methods including high-performance liquid chromatography (HPLC), thin-layer chromatography (TLC) and ion exchange chromatography (IEX) can be used to determine activities of c-di-AMP-synthesizing and degrading enzymes. Here, we describe in detail the TLC and IEX methods adapted for characterization of the diadenylate cyclase DisA and the phosphodiesterase AtaC from Streptomyces venezuelae. TLC allows quick and easy separation of radioactive-labeled substrates and products, while IEX avoids utilization of potentially hazardous radioactive substrates and can be used as a good substitute if an HPLC system is not available. Unlike in TLC assays, samples cannot be analyzed in parallel by using the IEX assay, thus it is more time consuming.

Selective saturation of step-edges as a tool to control the growth of molecular fibres.

The concept of bottom-up self-organisation has become a promising alternative for structuring molecular materials, which are hardly accessible by conventional top-down approaches such as lithography due to their limited chemical robustness. While these materials often tend to form three-dimensional, crystalline islands or fibres upon film growth, the size and orientation of such fibres are mainly governed by appropriate preparation conditions as well as microscopic interactions at the interface with the supporting surface. Substrate surface defects such as vacancies or step-edges, which cannot be completely ruled out on real surfaces on the mesoscopic scale, can act as preferred nucleation sites for molecules that leads to parasitic film growth competing with their intrinsic alignment prevailing on an ideal surface. In the present study, we demonstrate for the case of para-quaterphenyl (p-4P) that the presence of azimuthally disordered, fibres on Ag(111) surfaces can be understood as a superposition of step-mediated nucleation and the intrinsic epitaxial fibre growth on ideal surfaces. We validate the concept by purposely exposing the silver substrates briefly to oxygen or even ambient air to passivate the more reactive step-sites, which hampers subsequently grown molecular films to nucleate at these step-edges. This yields a truly epitaxial alignment as well as an enlargement of the fibres present on the whole sample.

Charge Transfer Excitation and Asymmetric Energy Transfer at the Interface of Pentacene-Perfluoropentacene Heterostacks.

High-performance solar cells demand efficient charge-carrier excitation, separation, and extraction. These requirements hold particularly true for molecular photovoltaics, where large exciton binding energies render charge separation challenging at their commonly complex donor-acceptor interface structure. Among others, charge-transfer (CT) states are considered to be important precursors for exciton dissociation and charge separation. However, the general nature of CT excitons and their formation pathways remain unclear. Layered quasiplanar crystalline molecular heterostructures of the prototypical donor-acceptor system pentacene-perfluoropentacene studied at cryogenic temperatures are a paramount model system to gain insights into the underlying physical mechanism. In particular, a detailed experiment-theory analysis on a layered heterojunction featuring perfluoropentacene in its π-stacked polymorph and pentacene in the Siegrist phase indicates that exciton diffusion in unitary films can influence the formation efficiency of CT excitons localized at internal interfaces for these conditions. The correlation of the structural characteristics, that is, the molecular arrangement at the interfaces, with their absorption and photoluminescence excitation spectra is consistent with exciton transfer from pentacene to the CT exciton state only, whereas no transfer of excitons from the perfluoropentacene is detected. Electronic structure calculations of the model systems and investigation of coupling matrix elements between the various electronic states involved suggest hampered exciton diffusion toward the internal interface in the perfluoropentacene films. The asymmetric energy landscape around an idealized internal donor-acceptor interface thus is identified as a reason for asymmetric energy transfer. Thus, long-range effects apparently can influence charge separation in crystalline molecular heterostructures, similar to band gap bowing, which is well established for inorganic pn-junctions.

Pentacene/perfluoropentacene bilayers on Au(111) and Cu(111): impact of organic-metal coupling strength on molecular structure formation.

As crucial element in organic opto-electronic devices, heterostructures are of pivotal importance. In this context, a comprehensive study of the properties on a simplified model system of a donor-acceptor (D-A) bilayer structure is presented, using ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED) and normal-incidence X-ray standing wave (NIXSW) measurements. Pentacene (PEN) as donor and perfluoropentacene (PFP) as acceptor material are chosen to produce bilayer structures on Au(111) and Cu(111) by sequential monolayer deposition of the two materials. By comparing the adsorption behavior of PEN/PFP bilayers on such weakly and strongly interacting substrates, it is found that: (i) the adsorption distance of the first layer (PEN or PFP) indicates physisorption on Au(111), (ii) the characteristics of the bilayer structure on Au(111) are (almost) independent of the deposition sequence, and hence, (iii) in both cases a mixed bilayer is formed on the Au substrate. This is in striking contrast to PFP/PEN bilayers on Cu(111), where strong chemisorption pins PEN molecules to the metal surface and no intermixing is induced by subsequent PFP deposition. The results illustrate the strong tendency of PEN and PFP molecules to mix, which has important implications for the fabrication of PEN/PFP heterojunctions.

Structural basis for sequestration and autoinhibition of cGAS by chromatin.

Cyclic GMP-AMP synthase (cGAS) is an innate immune sensor for cytosolic microbial DNA1. After binding DNA, cGAS synthesizes the messenger 2'3'-cyclic GMP-AMP (cGAMP)2-4, which triggers cell-autonomous defence and the production of type I interferons and pro-inflammatory cytokines via the activation of STING5. In addition to responding to cytosolic microbial DNA, cGAS also recognizes mislocalized cytosolic self-DNA and has been implicated in autoimmunity and sterile inflammation6,7. Specificity towards pathogen- or damage-associated DNA was thought to be caused by cytosolic confinement. However, recent findings place cGAS robustly in the nucleus8-10, where tight tethering of chromatin is important to prevent autoreactivity to self-DNA8. Here we show how cGAS is sequestered and inhibited by chromatin. We provide a cryo-electron microscopy structure of the cGAS catalytic domain bound to a nucleosome, which shows that cGAS does not interact with the nucleosomal DNA, but instead interacts with histone 2A-histone 2B, and is tightly anchored to the 'acidic patch'. The interaction buries the cGAS DNA-binding site B, and blocks the formation of active cGAS dimers. The acidic patch robustly outcompetes agonistic DNA for binding to cGAS, which suggests that nucleosome sequestration can efficiently inhibit cGAS, even when accessible DNA is nearby, such as in actively transcribed genomic regions. Our results show how nuclear cGAS is sequestered by chromatin and provides a mechanism for preventing autoreactivity to nuclear self-DNA.

C-Terminal Motifs of the MTW1 Complex Cooperatively Stabilize Outer Kinetochore Assembly in Budding Yeast.

Kinetochores are macromolecular protein assemblies at centromeres that mediate accurate chromosome segregation during cell division. The outer kinetochore KNL1SPC105, MIS12MTW1, and NDC80NDC80 complexes assemble the KMN network, which harbors the sites of microtubule binding and spindle assembly checkpoint signaling. The buildup of the KMN network that transmits microtubule pulling forces to budding yeast point centromeres is poorly understood. Here, we identify 225 inter-protein crosslinks by mass spectrometry on KMN complexes isolated from Saccharomyces cerevisiae that delineate the KMN subunit connectivity for outer kinetochore assembly. C-Terminal motifs of Nsl1 and Mtw1 recruit the SPC105 complex through Kre28, and both motifs aid tethering of the NDC80 complex by the previously reported Dsn1 C terminus. We show that a hub of three C-terminal MTW1 subunit motifs mediates the cooperative stabilization of the KMN network, which is augmented by a direct NDC80-SPC105 association.

Van der Waals Bound Organic/2D Insulator Hybrid Structures: Epitaxial Growth of Acene Films on hBN(001) and the Influence of Surface Defects.

Combining 2D materials with functional molecular films enables the fabrication of van der Waals bound organic/inorganic hybrids that are of interest for future device architectures. Recently, the 2D dielectric hexagonal boron nitride (hBN) has received particular attention since exfoliation allows the preparation of crystalline layers which have been utilized as ultrathin dielectrics in electronic devices. Here, we have studied the formation and structure of molecular films of the prototypical organic semiconductors pentacene (PEN) and perfluoropentacene (PFP) on hBN. Special attention was paid to the influence of substrate surface defects on the film formation by comparing molecular films that were grown on hBN substrates of various quality, including single crystals (representing the most ideal surface), briefly ion bombarded substrates, and exfoliated flakes. While X-ray diffraction (XRD) yields precise information about the crystalline structure of films grown on (large) single crystals, it is hardly applicable to analyze the films formed on exfoliated flakes because of their small size. Here, we demonstrate that in the case of flakes detailed structural analyses of the molecular films are possible by combining atomic force microscopy (AFM) with microspot UV/vis spectroscopy and optical polarization microscopy. On well-ordered hBN single crystal surfaces both acenes form very smooth and epitaxial crystalline films where molecules adopt a recumbent orientation (even in 100 nm thick films). By contrast, both materials adopt an upright molecular orientation and different polymorphs on defective hBN surfaces and reveal distinctly different film morphologies. On exfoliated flakes, PFP shows a film structure similar to that on the hBN single crystals, while PEN films exhibit a structure as on defective hBN substrates. In addition, a pronounced decoration of defect steps, which are probably created by the exfoliation process, was observed for PEN leading to the formation of tall and extended fibers where molecules adopt a recumbent orientation. The present study reveals different robustness in film growth on exfoliated hBN flakes for various molecules, which has to be considered in their device integration, especially with regard to their optoelectronic properties such as light absorption or charge transport, which depend critically on the molecular orientation and crystalline order.

Unilaterally Fluorinated Acenes: Synthesis and Solid-State Properties.

The rapid development of organic electronics is closely related to the availability of molecular materials with specific electronic properties. Here, we introduce a novel synthetic route enabling a unilateral functionalization of acenes along their long side, which is demonstrated by the synthesis of 1,2,10,11,12,14-hexafluoropentacene (1) and the related 1,2,9,10,11-pentafluorotetracene (2). Quantum chemical DFT calculations in combination with optical and X-ray absorption spectroscopy data indicate that the single-molecule properties of 1 are a connecting link between the organic semiconductor model systems pentacene (PEN) and perfluoropentacene (PFP). In contrast, the crystal structure analysis reveals a different packing motif than for the parent molecules. This can be related to distinct F⋅⋅⋅H interactions identified in the corresponding Hirshfeld surface analysis and also affects solid-state properties such as the exciton binding energy and the sublimation enthalpy.