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Ionic discotic liquid crystals combine ion conduction with fluid, yet ordered, liquid crystal phases at ambient temperature, making them suitable nanomaterials for ion transport and energy storage. A series of Janus-type hexa-peri-hexabenzocoronenes (HBCs) with ionic (sulfonate) groups covalently bonded to the HBC core, and tetraalkylammonium counterions (sizes from 0.15 to 0.95 nm) are synthesized and investigated with respect to the self-assembly and ion dynamics. We find that the counterion size affects the nanoscale self-assembly and ionic conductivity in opposite ways. Smaller counterions act as structure formers, whereas larger ones act as structure breakers. The latter exhibits the highest ion dc-conductivity. We quantify the effect of Coulomb interactions on the self-assembly, the glass temperature Tg (which was found to vary by 30 K), and the dc-conductivity (varying by 4 orders of magnitude). The precise synthesis of tailor-made ionic discotic liquid crystals with the HBC core and the characterization of their physical properties revealed that ion-conduction and nanoscale self-assembly in HBCs can be modulated by tuning electrostatic interactions, e.g., by adjusting the size of counterions. [ABSTRACT FROM AUTHOR]

The photooxidative stability of a series of doubly bridged anthracenes was evaluated after their preparation via twofold macrocyclization of a bis(resorcinyl)anthracene. Lightfastness correlates with the energy levels of the highest occupied molecular orbital (HOMO), resulting in superior stability of the tetraesters compared to the tetraethers. The lengths and steric demand of the linker only plays a minor role for the ester‐based compounds, which can be prepared in reasonable yields and thus tested in proof‐of‐concept organic light‐emitting diodes. Double ester‐bridging allows deep blue electro‐luminescence, highlighting the importance of the choice of the functional groups used for macrocyclization. [ABSTRACT FROM AUTHOR]

Four substituted nonacenes were prepared and characterized by UV‐vis and EPR spectroscopy and X‐ray crystallography. The compounds are the most stable and soluble nonacenes to date – due to six strategically placed triisopropylsilyl(TIPS)‐ethynyl groups. They are stable for several weeks in the solid state. In dilute solution their half‐life is 5–9 h. Crystal structure analyses of two nonacenes prove their structures. A nonacene derivative was tested in a solution‐processed transistor and exhibits ambipolar charge transport (μe=0.007 cm2/Vs; μh=0.023 cm2/Vs). [ABSTRACT FROM AUTHOR]

Two series of regioisomeric dicyanomethylene substituted dithienodiazatetracenes with formal para‐ or ortho‐quinodimethane subunits were synthesized and characterized. Whereas the para‐isomers (p‐n, diradical index y0=0.01) are stable and isolable, the ortho‐isomer (y0=0.98) dimerizes into a covalent azaacene cage. Four elongated σ‐CC bonds are formed and the former triisopropylsilyl(TIPS) ‐ethynylene groups transformed into cumulene units. The azaacene cage dimer (o‐1)2 was characterized by X‐ray single crystal structure analysis and temperature‐dependent infrared (IR), electron paramagnetic resonance (EPR, solid‐state), nuclear magnetic resonance (NMR) and ultraviolet‐visible (UV/Vis) spectroscopies (solution) indicating reformation of o‐1. [ABSTRACT FROM AUTHOR]

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We present the synthesis of two sets of spiro‐connected azaacene dimers. Their geometry and electronic coupling are critically determined by a secondary linker, i. e. an etheno‐ and an ethano‐bridge. The core fragment of the etheno‐bridged dimer corresponds to a conformationally locked cis‐stilbene. Optoelectronic properties, single crystal X‐ray structures and stability with respect to oxidation of the conjugated and non‐conjugated dimers are reported and compared. The conjugated dimers exhibit smaller optical gaps and bathochromically shifted absorption maxima, but are prone to unexpected oxygen addition, dearomatizing one of the azaacene substituents. [ABSTRACT FROM AUTHOR]

We report the synthesis and optoelectronic properties of 16 thiophene‐based heterophenoquinones. These compounds were accessed in a convergent and modular approach, allowing for their efficient synthesis. Tuning of the optical band gap was achieved through π‐extension by annulation of a benzene or tropone moiety to the thiophene, oxidation, change of the heteroatom or by attachment of a donor substituent to the thiophene core. The resulting compounds display intense colors covering the entire visible spectrum. We identified structure‐property relationships and their impact on the HOMO and LUMO levels. Additionally, these materials change color upon reduction and according to in situ ultraviolet‐visible‐near infrared (UV‐vis‐NIR) and electron paramagnetic resonance (EPR) spectro‐electrochemistry, they are promising electrochromes with cathodic color changes. Seven different electrochromic devices were constructed which all displayed a change in color upon reduction, demonstrating the potential of these new dyes in for example tintable glass. [ABSTRACT FROM AUTHOR]

Singlet fission is slowed down on diffusional timescales in highly concentrated solutions compared to thin films for a tetracene-like molecule. The underlying mechanism suggests competing intersystem crossing and singlet fission, where in the latter singlets are converted directly to triplets without an intermediate excimer state.

An oxidation reaction of hydroxyhomosumanene on silica gel providing homosumanene ortho‐quinone and its synthetic application for azaacene‐fused homosumanenes is described. Hydroxyhomosumanene is photochemically oxidized by air, when it is coated on silica gel; this aerobic oxidation proceeds faster than that of planar analogues. The difference of such reactivity was attributed to the unusual keto‐enol tautomerization due to structural difference between planar and curved π‐system. The homosumanene ortho‐quinone was used in the synthesis of several azaacene‐fused homosumanenes, azaacenohomosumanenes. X‐ray diffraction analysis of the single crystals revealed their columnar stacking structures due to the interactions between each bowl. Azaacenohomosumanenes exhibited high electron affinity due to the combination of buckybowl and electron‐deficient azaacene moieties. [ABSTRACT FROM AUTHOR]

Cyclopentannulation was explored as a strategy to access large, stable azaarenes. Buchwald–Hartwig coupling of previously reported di‐ and tetrabrominated cyclopentannulated N,N′‐dihydrotetraazapentacenes furnished stable azaarenes with up to 13 six‐membered rings in a row and a length of 3.1 nm. Their optoelectronic and semi‐conducting properties as well as their aromaticity were investigated. [ABSTRACT FROM AUTHOR]