Hydrogen bonds can efficiently guide the self-assembly of organic materials, enabling to tune the properties of the aggregation processes. In the case of p-conjugated materials, several parameters such as temperature, concentration and solvent can be used to modify the aggregation state while tuning the optoelectronic properties. Chirality can be included within the impacting parameters due to the differences in molecular packing. Here, chiral and achiral thiophene-capped diketopyrrolopyrrole derivatives were designed and synthesized containing amide bonds, with the aim to study the interplay between chiral assemblies and their stabilization throughh ydrogen-bonding. Differences in aggregation properties were observed with spectroscopy and microscopy,a nd ac ontactless microwave-based technique was used to study their intrinsic chargec arrierm obility.T he positive role of hydrogen-bonding has been highlighted and the differences between chiral and achiral compoundsh ave been elucidated.
Hydrogen bonds are noncovalent interactions able to improve the electronic properties of self-assembled semiconductors. Nevertheless, it is necessary to control the parameters influencing the formation of hydrogen bonds to achieve hierarchical structures with enhanced properties. In this work, we explore two hydrogen-bonded thiophene-capped diketopyrrolopyrrole (DPP) derivatives containing amides with different topology (C- or N-centered) and compare them to a control analogue without hydrogen bonds. We demonstrate the differences in the optoelectronic and self-assembly properties of the two amide-containing DPP derivatives, as well as in their charge carrier lifetimes. We prove the superior properties of the hydrogen-bonded derivatives in comparison to the control molecule without hydrogen bonds, and show that our molecular design strategy results in supramolecular structures with particularly long charge carrier lifetimes compared to other amide-containing semiconductors reported in the literature.
Some organic compounds are known to self-assemble into nanotubes in solutions, but the packing of the molecules into the walls of the tubes is known only in a very few cases. Herein, we study two compounds forming nanotubes in alkanes. They bear a secondary alkanamide chain linked to a benzoic acid propyl ester (HUB-3) or to a butyl ester (HUB-4). They gel alkanes for concentrations above 0.2 wt.%. The structures of these gels, studied by freeze fracture electron microscopy, exhibit nanotubes: for HUB-3 their external diameters are polydisperse with a mean value of 33.3 nm; for HUB-4, they are less disperse with a mean value of 25.6 nm. The structure of the gel was investigated by small- and wide-angle X-ray scattering. The evolution of the intensities show that the tubes are metastable and transit slowly toward crystals. The intensities of the tubes of HUB-4 feature up to six oscillations. The shape of the intensities proves the tubular structure of the aggregates, and gives a measurement of 20.6 nm for the outer diameters and 11.0 nm for the inner diameters. It also shows that the electron density in the wall of the tubes is heterogeneous and is well described by a model with three layers.
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