Chiral π-conjugated molecules have potential applications in spin-selective organic semiconductors and chiroptical electronic devices that are responsive to circularly polarized light. Their performance is expected to largely depend on how they assemble in the solid state, however, there are limited strategies for controlling the packing structure, particularly in helically-twisted π-conjugated molecules. In this work, a homochiral face-to-face columnar packing arrangement for helicene derivatives was achieved by modifying their helical ends with 2,1,3-thiadiazole structures. The observations provide useful insights into the chiral crystal engineering with helically twisted molecules and the development of chiral organic semiconductor materials.

Microcrystal electron diffraction（MicroED）is a technique that provides researchers with three-dimensional molecular structures from submicron-order crystals because the interaction between electrons and material is thousands of times stronger than that of X-rays. Additional advantage of this strong interaction is multiple scattering. Multiple scattering is highly sensitive to the three-dimensional arrangement of atoms, therefore by employing structural refinement based on dynamical diffraction theory, it becomes possible to determine the absolute structure of crystals. In this paper, we introduce characteristics of MicroED, some critical points for measurement and structure analysis, and examples of structure determination using an instrument dedicated to MicroED.

Three-dimensional electron diffraction（3D ED）, also known as microcrystal electron diffraction（MicroED）, has emerged as a powerful technique for determining the structures of ultra-thin protein crystals. Originally developed for protein crystallography, 3D ED/MicroED was subsequently demonstrated to be applicable to small-molecule crystallography for the micrometer-scale crystals. In this manuscript, we describe the development of a semi-automated 3D ED/MicroED data collection and processing system at the University of Tsukuba and its operation as a shared-use facility.

This work successfully demonstrated the crystal structure determination of large π-conjugated molecules using Micro-crystal Electron Diffraction（MicroED）. The poorly soluble tweezer-shaped molecules were synthesized, and their crystal structures were determined directly from the reaction vessels to MicroED, bypassing sample purification steps such as column chromatography and recrystallization. MicroED would be a powerful analytical tool for determining the structures of molecules and their assemblies for microcrystals, such as poorly soluble compounds, rare natural products, mechanochemical products, and membrane proteins. In this paper, we also report on the establishment of the MicroED techniques in Okazaki, detailing the preliminary experiments conducted for system startup, which included sample preparation, sample loading, calibration, data measurement, and data reduction.