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Using a thermodynamic database approach (CALPHAD), thermodynamic parameters of crystal growth of 31 stoichiometric and non-stoichiometric glasses are calculated. Together with these parameters, the measured growth rates, taken from both literature and in-house measurements, are interpreted in the framework of four interface-controlled growth models: normal, screw-dislocation, 2D growth and a combination of the latter two. A multiple linear regression model is used to explain the maximum crystal growth rate and viscosity at the liquidus temperature with the above growth mechanisms. This finding seems to reflect a general trend and can therefore be used to avoid unintentional devitrification phenomena or to derive their temperature-time range based on the sole knowledge of glass viscosity and liquidus temperature. In future research, it can also help to reduce the experimental workload required for the development of novel glasses and glass-ceramics. [Display omitted] [ABSTRACT FROM AUTHOR]

A series of cruciform aryl‐substituted quinoxalinophenanthrophenazine derivatives (QPPs) was synthesized through Suzuki‐Miyaura cross‐coupling of a 2,7‐diborylated pyrene tetraketal building block. The QPPs were analyzed for their optoelectronic properties by absorption and emission spectroscopy, cyclic voltammetry and quantum‐chemical calculations. The solid‐state packing was investigated as well and evaluated for its charge transport properties by calculated charge transfer integrals. [ABSTRACT FROM AUTHOR]

In materials chemistry of polycyclic aromatic compounds (PACs) the kind of aggregation and the spatial arrangement of the π‐planes are of utmost importance, e. g. for charge transport properties. Unfortunately, controlling these during crystallization is not trivial. In the past decade, we have introduced one‐fold triptycene end‐capping of quinoxalinophenanthrophenazines (QPPs) and other related structures to overcome this problem. When two instead of one triptycene end‐caps are introduced, packing is largely suppressed, making typical PACs or pigments soluble in common organic solvents – which is another important property for such compounds to be processable from solution. In this account an overview of our research on using triptycene end‐capping as dual strategy is given. [ABSTRACT FROM AUTHOR]

A six‐step synthesis towards a tribenzotriquinacene (TBTQ) bearing three quinoxalinophenanthrophenazine (QPP) units is presented. The optoelectronic properties are investigated and the effect of the three‐dimensional arrangement of the individual QPP planes is examined using optical spectroscopy, electrochemical analysis and quantum‐chemical calculations. [ABSTRACT FROM AUTHOR]

Previously it was demonstrated that triptycene end‐capping can be used as a crystal engineering strategy to direct the packing of quinoxalinophenanthrophenazines (QPPs) towards cofacially stacked π dimers with large molecular overlap resulting in high charge transfer integrals. Remarkably, this packing motif was formed under different crystallization conditions and with a variety of derivatives bearing additional functional groups or aromatic substituents. Benzothienobenzothiophene (BTBT) and its derivatives are known as some of the best performing compounds for organic field‐effect transistors. Here, the triptycene end‐capping concept is introduced to this class of compounds and polymorphic crystal structures are investigated to evaluate the potential of triptycene end‐caps as synthons for crystal engineering. [ABSTRACT FROM AUTHOR]

Five di‐ and tetracyano‐substituted pyrene‐fused pyrazaacenes were synthesized and studied as potential electron acceptors in the solid state. Single crystals of all compounds were grown and the crystal packing studied by DFT calculations (transfer integrals and reorganization energies) to get insight into possible use for semiconducting charge transport. [ABSTRACT FROM AUTHOR]

Triptycene end‐capped quinoxalinophenanthrophenazine reveals a coplanar arrangement with a high overlap of the π planes. Four structurally related model compounds bearing electron‐withdrawing or ‐donating groups were synthesized, and their optoelectronic properties were characterized by using cyclovoltammetry, absorption‐ and emission spectroscopy as well as theoretical calculations. The directional robustness of the triptycene end‐capping of these compounds was tested by using single‐crystal X‐ray diffraction. The impact of solvents and crystallization conditions has also been investigated. In total, 17 single‐crystal structures were obtained. Each structure was evaluated for its potential charge‐transfer capability taking into account the overall molecular packing, solvent enclathration and the structural overlap of the π planes of adjacent molecules. For this purpose, charge‐transfer integrals were also calculated for every π‐stacked dimer. [ABSTRACT FROM AUTHOR]

Liquid exfoliation and centrifugation based size selection has emerged as widely applied technique to produce nanosheets in a solution-processable form. Quantitative spectroscopic metrics to extract nanosheet size, thickness and monolayer content from optical spectra have previously been established. Such metrics are extremely useful and can be used to optimise the production technique (for example on scale-up) and size selection. However, it is not clear whether exfoliation, size selection, and spectroscopic metrics are robust or whether the result depends on the starting material or subtle details of the processing and analysis. By comparing two batches of WS2 exfoliated and size-selected in aqueous surfactant solution using different starting materials, protocols and equipment in each step, we show that the nanosheet size obtained after different steps in a cascade centrifugation is highly reproducible. A detailed statistical analysis on the nanosheet dimensions revealed well-defined relationships between nanosheet mean thickness and monolayer content. Spectroscopic metrics for nanosheet layer number, lateral size (from extinction) and monolayer content (from Raman/photoluminescence) do not depend on sample type and measurement conditions, albeit the data analysis may require adjustment as discussed. [ABSTRACT FROM AUTHOR]