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The charge‐transfer (CT) interactions between organic compounds are reflected in the (opto)electronic properties. Determining and visualizing crystal structures of CT complexes are essential for the design of functional materials with desirable properties. Complexes of pyranine (PYR), methyl viologen (MV), and their derivatives are the most studied water‐based CT complexes. Nevertheless, very few crystal structures of CT complexes have been reported so far. In this study, the structures of two PYRs‐MVs CT crystals and a map of the noncovalent interactions using 3D electron diffraction (3DED) are reported. Physical properties, e.g., band structure, conductivity, and electronic spectra of the CT complexes and their crystals are investigated and compared with a range of methods, including solid and liquid state spectroscopies and highly accurate quantum chemical calculations based on density functional theory (DFT). The combination of 3DED, spectroscopy, and DFT calculation can provide important insight into the structure‐property relationship of crystalline CT materials, especially for submicrometer‐sized crystals. [ABSTRACT FROM AUTHOR]

SnGe4N4O4 was synthesized at high pressure (16 and 20 GPa) and high temperature (1200 and 1500°C) in a large‐volume press. Powder X‐ray diffraction experiments using synchrotron radiation indicate that the derived samples are mixtures of known and unknown phases. However, the powder X‐ray diffraction patterns are not sufficient for structural characterization. Transmission electron microscopy studies reveal crystals of several hundreds of nanometres in size with different chemical composition. Among them, crystals of a previously unknown phase with stoichiometry SnGe4N4O4 were detected and investigated using automated diffraction tomography (ADT), a three‐dimensional electron diffraction method. Via ADT, the crystal structure could be determined from single nanocrystals in space group P63mc, exhibiting a nolanite‐type structure. This was confirmed by density functional theory calculations and atomic resolution scanning transmission electron microscopy images. In one of the syntheses runs a rhombohedral 6R polytype of SnGe4N4O4 could be found together with the nolanite‐type SnGe4N4O4. The structure of this polymorph was solved as well using ADT. [ABSTRACT FROM AUTHOR]

Beauveriolides, including the main beauveriolide I {systematic name: (3R,6S,9S,13S)‐9‐benzyl‐13‐[(2S)‐hexan‐2‐yl]‐6‐methyl‐3‐(2‐methylpropyl)‐1‐oxa‐4,7,10‐triazacyclotridecane‐2,5,8,11‐tetrone, C27H41N3O5}, are a series of cyclodepsipeptides that have shown promising results in the treatment of Alzheimer's disease and in the prevention of foam cell formation in atherosclerosis. Their crystal structure studies have been difficult due to their tiny crystal size and fibre‐like morphology, until now. Recent developments in 3D electron diffraction methodology have made it possible to accurately study the crystal structures of submicron crystals by overcoming the problems of beam sensitivity and dynamical scattering. In this study, the absolute structure of beauveriolide I was determined by 3D electron diffraction. The cyclodepsipeptide crystallizes in the space group I2 with lattice parameters a = 40.2744 (4), b = 5.0976 (5), c = 27.698 (4) Å and β = 105.729 (6)°. After dynamical refinement, its absolute structure was determined by comparing the R factors and calculating the z‐scores of the two possible enantiomorphs of beauveriolide I. [ABSTRACT FROM AUTHOR]

Tetrakis‐4‐(4‐pyridyl)phenylmethane (TPPM) is a tetrahedral rigid molecule that crystallizes forming a dynamically responsive supramolecular organic framework (SOF). When exposed to different stimuli, this supramolecular network can reversibly switch from an empty to a filled solvated solid phase. This article describes a novel expanded form of a TPPM‐based SOF that has been mechanochemically synthesized and whose crystal structure has been determined by 3D electron diffraction analysis using a novel electron diffractometer. [ABSTRACT FROM AUTHOR]

Levocetirizine is an orally administrated, second‐generation antihistaminic active pharmaceutical ingredient that has been used to treat symptoms of allergy and long‐term hives for over 25 years. Despite the wide use of this compound, its crystal structure has remained unknown. Here we report the application of 3D electron diffraction (3D ED)/Micro‐crystal electron diffraction (MicroED) to determine the crystal structure of Levocetirizine dihydrochloride directly from crystalline powders that were extracted from commercially available tablets containing the compound. We also showcase the utility of dynamical refinement to unambiguously assign absolute configuration. The results highlight the immense potential of 3D ED/MicroED for structure elucidation of components of microcrystalline mixtures that obviates the need to grow large‐size single crystals and the use of complementary analytical techniques, which could be important for identification as well as for primary structural characterization. [ABSTRACT FROM AUTHOR]

The crystallographic study of two polymorphs of the industrial pyrazolone Pigment Orange 13 (P.O.13) is reported. The crystal structure of the β phase was determined using single‐crystal X‐ray analysis of a tiny needle. The α phase was investigated using three‐dimensional electron diffraction. The electron diffraction data contain sharp Bragg reflections and strong diffuse streaks, associated with severe stacking disorder. The structure was solved by careful analysis of the diffuse scattering, and similarities of the unit‐cell parameters with the β phase. The structure solution is described in detail and this provides a didactic example of solving molecular crystal structures in the presence of diffuse scattering. Several structural models were constructed and optimized by lattice‐energy minimization with dispersion‐corrected DFT. A four‐layer model was found, which matches the electron diffraction data, including the diffuse scattering, and agrees with X‐ray powder data. Additionally, five further phases of P.O.13 are described. [ABSTRACT FROM AUTHOR]

The crystallographic study of two polymorphs of the industrial pyrazolone Pigment Orange 13 (P.O.13) is reported. The crystal structure of the β phase was determined using single‐crystal X‐ray analysis of a tiny needle. The α phase was investigated using three‐dimensional electron diffraction. The electron diffraction data contain sharp Bragg reflections and strong diffuse streaks, associated with severe stacking disorder. The structure was solved by careful analysis of the diffuse scattering, and similarities of the unit‐cell parameters with the β phase. The structure solution is described in detail and this provides a didactic example of solving molecular crystal structures in the presence of diffuse scattering. Several structural models were constructed and optimized by lattice‐energy minimization with dispersion‐corrected DFT. A four‐layer model was found, which matches the electron diffraction data, including the diffuse scattering, and agrees with X‐ray powder data. Additionally, five further phases of P.O.13 are described. [ABSTRACT FROM AUTHOR]

Three‐dimensional electron diffraction (3D ED) has become an effective technique to determine the structures of submicrometre‐ (nanometre‐)sized crystals. In this work, energy‐filtered 3D ED was implemented using a post‐column energy filter in both STEM mode and TEM mode [(S)TEM denoting (scanning) transmission electron microscope]. The setups for performing energy‐filtered 3D ED on a Gatan imaging filter are described. The technique and protocol improve the accessibility of energy‐filtered 3D ED post‐column energy filters, which are available in many TEM laboratories. In addition, a crystal tracking method in STEM mode using high‐angle annular dark‐field imaging is proposed. This method enables the user to monitor the crystal position while collecting 3D ED data at the same time, allowing a larger tilt range without foregoing any diffraction frames or imposing extra electron dose. In order to compare the differences between energy‐filtered and unfiltered 3D ED data sets, three well known crystallized inorganic samples have been studied in detail. For these samples, the final R1 values improved by 10–30% for the energy‐filtered data sets compared with the unfiltered data sets, and the structures became more chemically reasonable. Possible reasons for improvement are also discussed. [ABSTRACT FROM AUTHOR]

Nanomedicine is among the most fascinating areas of research. Most of the newly discovered pharmaceutical polymorphs, as well as many new synthesized or isolated natural products, appear only in form of nanocrystals. The development of techniques that allow investigating the atomic structure of nanocrystalline materials is therefore one of the most important frontiers of crystallography. Some unique features of electrons, like their non‐neutral charge and their strong interaction with matter, make this radiation suitable for imaging and detecting individual atoms, molecules, or nanoscale objects down to sub‐angstrom resolution. In the recent years the development of three‐dimensional (3D) electron diffraction (3D ED) has shown that electron diffraction can be successfully used to solve the crystal structure of nanocrystals and most of its limiting factors like dynamical scattering or limited completeness can be easily overcome. This article is a review of the state of the art of this method with a specific focus on how it can be applied to beam sensitive samples like small‐molecule organic nanocrystals. This article is categorized under:Therapeutic Approaches and Drug Discovery > Emerging Technologies [ABSTRACT FROM AUTHOR]

SnGe 4 N 4 O 4 was synthesized at high pressure (16 and 20 GPa) and high temperature (1200 and 1500°C) in a large-volume press. Powder X-ray diffraction experiments using synchrotron radiation indicate that the derived samples are mixtures of known and unknown phases. However, the powder X-ray diffraction patterns are not sufficient for structural characterization. Transmission electron microscopy studies reveal crystals of several hundreds of nanometres in size with different chemical composition. Among them, crystals of a previously unknown phase with stoichiometry SnGe 4 N 4 O 4 were detected and investigated using automated diffraction tomography (ADT), a three-dimensional electron diffraction method. Via ADT, the crystal structure could be determined from single nanocrystals in space group P6 3 mc, exhibiting a nolanite-type structure. This was confirmed by density functional theory calculations and atomic resolution scanning transmission electron microscopy images. In one of the syntheses runs a rhombohedral 6R polytype of SnGe 4 N 4 O 4 could be found together with the nolanite-type SnGe 4 N 4 O 4 . The structure of this polymorph was solved as well using ADT., (open access.)

Copper perchlorophthalocyanine (CuPcCl16, CuC32N8Cl16, Pigment Green 7) is one of the commercially most important green pigments. The compound is a nanocrystalline fully insoluble powder. Its crystal structure was first addressed by electron diffraction in 1972 [Uyeda et al. (1972). J. Appl. Phys.43, 5181–5189]. Despite the commercial importance of the compound, the crystal structure remained undetermined until now. Using a special vacuum sublimation technique, micron‐sized crystals could be obtained. Three‐dimensional electron diffraction (3D ED) data were collected in two ways: (i) in static geometry using a combined stage‐tilt/beam‐tilt collection scheme and (ii) in continuous rotation mode. Both types of data allowed the crystal structure to be solved by direct methods. The structure was refined kinematically with anisotropic displacement parameters for all atoms. Due to the pronounced crystal mosaicity, a dynamic refinement was not feasible. The unit‐cell parameters were verified by Rietveld refinement from powder X‐ray diffraction data. The crystal structure was validated by many‐body dispersion density functional theory (DFT) calculations. CuPcCl16 crystallizes in the space group C2/m (Z = 2), with the molecules arranged in layers. The structure agrees with that proposed in 1972. [ABSTRACT FROM AUTHOR]

Microcrystal electron diffraction (MicroED) has recently emerged as a promising method for macromolecular structure determination in structural biology. Since the first protein structure was determined in 2013, the method has been evolving rapidly. Several protein structures have been determined and various studies indicate that MicroED is capable of (i) revealing atomic structures with charges, (ii) solving new protein structures by molecular replacement, (iii) visualizing ligand‐binding interactions and (iv) determining membrane‐protein structures from microcrystals embedded in lipidic mesophases. However, further development and optimization is required to make MicroED experiments more accurate and more accessible to the structural biology community. Here, we provide an overview of the current status of the field, and highlight the ongoing development, to provide an indication of where the field may be going in the coming years. We anticipate that MicroED will become a robust method for macromolecular structure determination, complementing existing methods in structural biology. [ABSTRACT FROM AUTHOR]

Structure determination of covalent organic frameworks (COFs) with atomic precision is a bottleneck that hinders the development of COF chemistry. Although three‐dimensional electron diffraction (3D‐ED) data has been used to solve structures of sub‐micrometer‐sized COFs, successful structure solution is not guaranteed as the data resolution is usually low. We demonstrate that the direct‐space strategy for structure solution, implemented using a genetic algorithm (GA), is a successful approach for structure determination of COF‐300 from 3D‐ED data. Structural models with different geometric constraints were considered in the GA calculations, with successful structure solution achieved from room‐temperature 3D‐ED data with a resolution as low as ca. 3.78 Å. The generality of this strategy was further verified for different phases of COF‐300. This study demonstrates a viable strategy for structure solution of COF materials from 3D‐ED data of limited resolution, which may facilitate the discovery of new COF materials in the future. [ABSTRACT FROM AUTHOR]

A DigitalMicrograph script, InsteaDMatic, has been developed to facilitate rapid automated 3D electron diffraction/microcrystal electron diffraction data acquisition by continuous rotation of a crystal with a constant speed, denoted as continuous rotation electron diffraction. The script coordinates microscope functions, such as stage rotation, and camera functions relevant for data collection, and stores the experiment metadata. The script is compatible with any microscope that can be controlled by DigitalMicrograph and has been tested on both JEOL and Thermo Fisher Scientific microscopes. A proof of concept has been performed through employing InsteaDMatic for data collection and structure determination of a ZSM‐5 zeolite. The influence of illumination settings and electron dose rate on the quality of diffraction data, unit‐cell determination and structure solution has been investigated in order to optimize the data acquisition procedure. [ABSTRACT FROM AUTHOR]

A novel crystalline high‐silica zeolite with 12×8‐membered ring (R) channel system is prepared with the aid of the 3D electron diffraction (3D ED) technique. A crystal with the same topology as one of the predicted daughter structures of CIT‐13 germanosilicate, named ECNU‐23 (East China Normal University 23) was coincidentally detected by the 3D ED investigation during the structure characterization of the "pure" powder sample of existing one‐dimension (1D) 10‐R ECNU‐21. By controlling the alkaline‐assisted hydrolysis under moderate conditions, we purified the phase of ECNU‐23 by selectively breaking and removing the chemically weak Ge(Si)‐O‐Ge and metastable Si‐O‐Si bonds. Its structure was determined based on the 3D ED data, and confirmed by high‐resolution TEM images and powder X‐ray diffraction (PXRD) data. The aluminosilicate Al‐ECNU‐23 shows unique catalytic properties in the isomerization/ disproportionation of m‐xylene as solid‐acid catalyst. [ABSTRACT FROM AUTHOR]

Orthocetamol is a regioisomer of the well‐known pain medication paracetamol and a promising analgesic and an anti‐arthritic medicament itself. However, orthocetamol cannot be grown as single crystals suitable for X‐ray diffraction, so its crystal structure has remained a mystery for more than a century. Here, we report the ab‐initio structure determination of orthocetamol obtained by 3D electron diffraction, combining a low‐dose acquisition method and a dedicated single‐electron detector for recording the diffracted intensities. The structure is monoclinic, with a pseudo‐tetragonal cell that favors multiple twinning on a scale of a few tens of nanometers. The successful application of 3D electron diffraction to orthocetamol introduces a new gold standard of total structure solution in all cases where X‐ray diffraction and electron‐microscope imaging methods fail. [ABSTRACT FROM AUTHOR]

Diffuse scattering, observed as intensity distribution between the Bragg peaks, is associated with deviations from the average crystal structure, generally referred to as disorder. In many cases crystal defects are seen as unwanted perturbations of the periodic structure and therefore they are often ignored. Yet, when it comes to the structure analysis of nano‐volumes, what electron crystallography is designed for, the significance of defects increases. Twinning and polytypic sequences are other perturbations from ideal crystal structure that are also commonly observed in nanocrystals. Here we present an overview of defect types and review some of the most prominent studies published on the analysis of defective nanocrystalline structures by means of three‐dimensional electron diffraction. [ABSTRACT FROM AUTHOR]

3D electron diffraction has reached a stage where the structures of chemical compounds can be solved productively. Instrumentation is lagging behind this development, and to date dedicated electron diffractometers for data collection based on the rotation method do not exist. Current studies use transmission electron microscopes as a workaround. These are optimized for imaging, which is not optimal for diffraction studies. The beam intensity is very high, it is difficult to create parallel beam illumination and the detectors used for imaging are of only limited use for diffraction studies. In this work, the combination of an EIGER hybrid pixel detector with a transmission electron microscope to construct a productive electron diffractometer is described. The construction not only refers to the combination of hardware but also to the calibration of the system, so that it provides rapid access to the experimental parameters that are necessary for processing diffraction data. Until fully integrated electron diffractometers become available, this describes a setup for productive and efficient operation in chemical crystallography. [ABSTRACT FROM AUTHOR]

The crystallographic study of two polymorphs of the industrial pyrazolone Pigment Orange 13 (P.O.13) is reported. The crystal structure of the β phase was determined using single-crystal X-ray analysis of a tiny needle. The α phase was investigated using three-dimensional electron diffraction. The electron diffraction data contain sharp Bragg reflections and strong diffuse streaks, associated with severe stacking disorder. The structure was solved by careful analysis of the diffuse scattering, and similarities of the unit-cell parameters with the β phase. The structure solution is described in detail and this provides a didactic example of solving molecular crystal structures in the presence of diffuse scattering. Several structural models were constructed and optimized by lattice-energy minimization with dispersion-corrected DFT. A four-layer model was found, which matches the electron diffraction data, including the diffuse scattering, and agrees with X-ray powder data. Additionally, five further phases of P.O.13 are described., (open access.)