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Historically, knowledge of the molecular packing within the crystal structures of organic semiconductors has been instrumental in understanding their solid-state electronic properties. Nowadays, crystal structures are thus becoming increasingly important for enabling engineering properties, understanding polymorphism in bulk and in thin films, exploring dynamics and elucidating phase-transition mechanisms. This review article introduces the most salient and recent results of the field., (open access.)

The lattice dynamics of organic semiconductors has a significant role in determining their electronic and mechanical properties. A common technique to control these macroscopic properties is to chemically modify the molecular structure. These modifications are known to change the molecular packing, but their effect on the lattice dynamics is relatively unexplored. Therefore, we investigate how chemical modifications to a core [1]benzothieno[3,2- b ]benzothiophene (BTBT) semiconducting crystal affect the evolution of the crystal structural dynamics with temperature. Our study combines temperature-dependent polarization-orientation (PO) low-frequency Raman measurements with first-principles calculations and single-crystal X-ray diffraction measurements. We show that chemical modifications can indeed suppress specific expressions of vibrational anharmonicity in the lattice dynamics. Specifically, we detect in BTBT a gradual change in the PO Raman response with temperature, indicating a unique anharmonic expression. This anharmonic expression is suppressed in all examined chemically modified crystals (ditBu-BTBT and diC8-BTBT, diPh-BTBT, and DNTT). In addition, we observe solid-solid phase transitions in the alkyl-modified BTBTs. Our findings indicate that π-conjugated chemical modifications are the most effective in suppressing these anharmonic effects., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Introduction of adamantane moieties on diamondoids such as adamantane, 2-azaadamantane or diamantane by amide formation and reduction to the corresponding amine was performed in a straightforward and easy way by amidation under Schotten-Baumann conditions and reduction with BH 3  ⋅ THF. The obtained amides and amines were studied in terms of structural properties towards the perspective of transformation into nanodiamonds. Crystal structure and dynamic NMR experiments of the most crowded amide obtained gave structural insights into the effect of bulkiness and steric strain on out-of-planarity of amide bonds (16.0°) and the kinetics and thermodynamics of amide bond rotation (ΔG ≠ 298K =11.5-13.3 kcal ⋅ mol -1 )., (© 2022 The Authors. Published by Wiley-VCH GmbH.)

We report 3 confirmed autochthonous tick-borne encephalitis cases in Belgium diagnosed during summer 2020. Clinicians should include this viral infection in the differential diagnosis for patients with etiologically unexplained neurologic manifestations, even for persons without recent travel history.

Martensitic transition is a solid-state phase transition involving cooperative movement of atoms, mostly studied in metallurgy. The main characteristics are low transition barrier, ultrafast kinetics, and structural reversibility. They are rarely observed in molecular crystals, and hence the origin and mechanism are largely unexplored. Here we report the discovery of martensitic transition in single crystals of two different organic semiconductors. In situ microscopy, single-crystal X-ray diffraction, Raman and nuclear magnetic resonance spectroscopy, and molecular simulations combined indicate that the rotating bulky side chains trigger cooperative transition. Cooperativity enables shape memory effect in single crystals and function memory effect in thin film transistors. We establish a molecular design rule to trigger martensitic transition in organic semiconductors, showing promise for designing next-generation smart multifunctional materials.

Thermal vibrations and the dynamic disorder they create can detrimentally affect the transport properties of van der Waals bonded molecular semiconductors. The low-energy nature of these vibrations makes it difficult to access them experimentally, which is why we still lack clear molecular design rules to control and reduce dynamic disorder. In this study we discuss the promising organic semiconductors rubrene, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothio-phene and 2,9-di-decyl-dinaphtho-[2,3-b:20,30-f]-thieno-[3,2-b]-thiophene in terms of an exceptionally low degree of dynamic disorder. In particular, we analyse diffuse scattering in transmission electron microscopy, to show that small molecules that have their side chains attached along the long axis of their conjugated core are better encapsulated in their crystal structure, which helps reduce large-amplitude thermal motions. Our work provides a general strategy for the design of new classes of very high mobility organic semiconductors with a low degree of dynamic disorder.

The fabrication of multifunctional high-performance organic thin-film transistors as key elements in future logic circuits is a major research challenge. Here we demonstrate that a photoresponsive bi-functional field-effect transistor with carrier mobilities exceeding 0.2 cm(2) V(-1) s(-1) can be developed by incorporating photochromic molecules into an organic semiconductor matrix via a single-step solution processing deposition of a two components blend. Tuning the interactions between the photochromic diarylethene system and the organic semiconductor is achieved via ad-hoc side functionalization of the diarylethene. Thereby, a large-scale phase-segregation can be avoided and superior miscibility is provided, while retaining optimal π-π stacking to warrant efficient charge transport and to attenuate the effect of photoinduced switching on the extent of current modulation. This leads to enhanced electrical performance of transistors incorporating small conjugated molecules as compared with polymeric semiconductors. These findings are of interest for the development of high-performing optically gated electronic devices.

A previously reported diketopyrrolopyrrole (DPP)-phenyl copolymer is modified by adding methoxy or octyloxy side chains on the phenyl spacer. The influence of these alkoxy substitutions on the physical, opto-electronic properties, and photovoltaic performance were investigated. It was found that the altered physical properties correlated with an increase in chain flexibility. Well-defined oligomers were synthesized to verify the observed structure-property relationship. Surprisingly, methoxy substitution on the benzene spacer resulted in higher melting and crystallization temperatures in the synthesized oligomers. This trend is not observed in the polymers, where the improved interactions are most likely counteracted by the larger conformational possibilities in the polymer chain upon alkoxy substitution. The best photovoltaic performance was obtained for the parent polymer: fullerene blends whereas the modifications on the other two polymers result in reduced open-circuit voltage and varying current densities under similar processing conditions. The current densities could be related to different polymer: fullerene blend morphologies. These results show that supposed small structural alterations such as methoxy substitution already significantly altered the physical properties of the parent polymer and also that oligomers and polymers respond divergent to structural alterations made on a parent structure.

The self-assembly of functional polythiophenes was studied by a bottom-up approach "from molecule to polymer". The synthesis and the X-ray structure of 2,5-dibromo-3-styryl and 3-2',3',4',5',6'-pentafluorostyryl-thiophenes revealed a supramolecular arrangement controlled by pi-pi interactions between the aromatic rings. A [2 + 2] photocyclization reaction in the solid state of (E)-1-2',5'-dibromo-3'-thienyl-2-pentafluorophenylethene triggers the formation of a rare cycloadduct comprising thiophene rings. The X-ray analysis confirmed its rctt stereochemistry. The synthesis of P3HT-b-P3ST and P3HT-b-P3STF block oligomers was achieved by a GRIM method in good yields. An indirect proof of well-defined nanostructured organization was provided by the partial photocyclization of pendant styryl moieties under UV irradiation.

Purpose: Extensive experience with video-EEG seizure monitoring, notably in the setting of epilepsy surgery programs, has exposed the limited value of the current International Classification of Epileptic Seizures (ICES) for providing relevant localizing information. To overcome this limitation, a Semiologic Seizure Classification (SSC) has recently been proposed. This study aimed to assess and to compare the usefulness and reliability of both systems in the setting of a tertiary epilepsy center., Methods: Three epileptologists independently reviewed video-taped seizures, randomly selected from the archive of the Epilepsy Monitoring Unit. They were blinded to the EEG findings and final diagnosis and classified all seizures according to both classifications., Results: One hundred thirty-eight seizures from 60 patients (age range, 2-59 years) were reviewed (maximum, three seizures per patient). Fifty-five seizures from 20 patients were recorded in the setting of presurgical evaluations, and the remainder as part of regular diagnostic evaluations. The average interobserver agreement was higher for SSC (63.3%, kappa = 0. 56) than for ICES (38.6%, kappa = 0.41). Some categories of SSC, such as hypermotor or automotor, had the best interobserver agreement, and were strongly correlated with the anatomic localization of the seizures (frontal and temporal lobe, respectively). All reviewers agreed that SSC provided a better description of the seizures than did ICES, in 60% of the patients., Conclusions: SSC provides a more comprehensive picture of epileptic seizures than does ICES, notably in patients with localized epilepsy syndromes, and appears to be very useful and reliable, particularly in the setting of specialized epilepsy centers.