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Along with the adoption of three-dimensional electron diffraction (3D ED/MicroED) as a mainstream tool for structure determination from sub-micron single crystals, questions about best practices regarding each step along the workflow, from data collection to structure solutions, arise. In this paper, we discuss three particular aspects of a 3D ED/MicroED experiment which, after hundreds of structures solved in Rigaku's laboratories, we have found to be important to consider carefully. First, for a representative model system of a hydrated compound (trehalose dihydrate), we show that cryo-transfer of the sample into the diffractometer is an effective means to prevent dehydration, while cooling of the sample without cryo-transfer yields a marginal improvement only. Next, we demonstrate for a small (tyrosine) and a large (clarithromycin) organic compound, how a simplified and fast workflow for dynamical diffraction calculations can determine absolute crystal structures with high confidence. Finally, we discuss considerations and trade-offs for choosing an optimal effective crystal-to-detector distance; while a long distance is mandatory for a protein (thaumatin) example, even a small molecule with difficult diffraction behavior (cystine) yields superior results at longer distances than the one used by default. [ABSTRACT FROM AUTHOR]

The synthesis of four novel gold(I)-phosphane complexes coordinated to 9-phenanthrene chromophore has been carried out through the reaction of 9-phenanthreneboronic acid and the corresponding AuClPR3 (PR3 = PPh3 for triphenylphosphane (1a); 1,4-bis(diphenylphosphanyl)butane or dppb (2b); bis(diphenylphosphanyl)acetylene or dppa (2c); (AuCl)2(diphos) (diphos = bis(diphenylphosphanyl)methane or dppm (3)) sources. The X-ray crystal structures of compounds 1a and 2b show the existence of MOF-like intermolecular assemblies that contain empty inner cavities in the absence of aurophilic contacts. In contrast, the formation of a tetranuclear complex with intramolecular aurophilic interactions was evidenced for 3. Photophysical characterization indicates dual emission in all gold(I) complexes when oxygen is removed from the sample, while only fluorescence emission is recorded for the uncoordinated ligand. The introduction of the compounds within PMMA and Zeonex was assayed, and luminescent films containing gold(I) complexes where phosphorescence is the sole pathway for emission are obtained, instead of the dual emission (with significant fluorescence contribution) recorded in solution. [ABSTRACT FROM AUTHOR]

The substituted acetylacetone 3‐[2‐(pyridin‐4‐yl)ethyl]pentane‐2,4‐dione, C12H15NO2, (1), with an ethylene bridge between the acetylacetone moiety and the heteroaromatic ring, represents an attractive linker for mixed‐metal coordination polymers. In the crystal, (1) adopts an antiperiplanar conformation with respect to the C—C bond in the central ethylene group and almost coplanar acetylacetone and pyridyl groups. The ditopic molecule exists as the enol tautomer, with proton disorder in the short intramolecular hydrogen bond. Single‐crystal neutron diffraction at 2.5 K indicated site occupancies of 0.602 (17) and 0.398 (17). The geometry of the acetylacetone moiety is in agreement with such a site preference of the bridging hydrogen: the O atom associated with the preferred H‐atom site subtends the longer [1.305 (2) Å] and the more carbonyl‐like O atom the shorter [1.288 (2) Å] C—O bond. Based on structure‐factor calculations for the alternative H‐atom sites, reflections particularly sensitive for proton distribution were identified and measured in a second neutron data collection at 170 K. At this temperature, 546 independent neutron intensities were used to refine positional and isotropic displacement parameters for a structure model in which parameters for C and O atoms were constrained to those obtained by single‐crystal X‐ray diffraction at the same temperature. The site occupancies for the disordered proton do not significantly differ from those at 2.5 K. Single‐crystal neutron diffraction at 2.5 K and a subset of neutron data collected at 170 K, combined with information from X‐ray diffraction at the same temperature, suggest static disorder for the proton in the short intramolecular hydrogen bond of 3‐[2‐(pyridin‐4‐yl)ethyl]pentane‐2,4‐dione. [ABSTRACT FROM AUTHOR]

3-(Pyridin-4-yl)acetylacetone (HacacPy) acts as a pyridine-type ligand towards CdII and HgII halides. With CdBr2, the one-dimensional polymer [Cd(μ-Br)2(HacacPy)Cd(μ-Br)2(HacacPy)2]∞ is obtained in which five- and six-coordinated CdII cations alternate in the chain direction. Reaction of HacacPy with HgBr2 results in [Hg(μ-Br)Br(HacacPy)]∞, a polymer in which each HgII centre is tetracoordinated. In both compounds, each metal(II) cation is N-coordinated by at least one HacacPy ligand. Equimolar reaction between these CdII and HgII derivatives, either conducted in ethanol as solvent or via grinding in the solid state, leads to ligand redistribution and the formation of the well-ordered bimetallic polymer catena-poly[[bromidomercury(II)]-μ-bromido-[aquabis[4-hydroxy-3-(pyridin-4-yl)pent-3-en-2-one]cadmium(II)]-di-μ-bromido], [CdHgBr4(C10H11NO2)2(H2O)] n or [{HgBr}(μ-Br){(HacacPy)2Cd(H2O)}(μ-Br)2]∞. HgII and CdII cations alternate in the [100] direction. The HacacPy ligands do not bind to the HgII cations, which are tetracoordinated by three bridging and one terminal bromide ligand. The CdII centres adopt an only slightly distorted octahedral coordination. Three bromide ligands link them in a (2 + 1) pattern to neighbouring HgII atoms; two HacacPy ligands in a cis configuration, acting as N-atom donors, and a terminal aqua ligand complete the coordination sphere. Classical O-H...Br hydrogen bonds stabilize the polymeric chain. O-H...O hydrogen bonds between aqua H atoms and the uncoordinated carbonyl group of an HacacPy ligand in a neighbouring strand in the c direction link the chains into layers in the (010) plane. [ABSTRACT FROM AUTHOR]

Depending on the reaction partner, the organic ditopic molecule isonicotinic acid (Hina) can act either as a Brønsted acid or base. With sulfuric acid, the pyridine ring is protonated to become a pyridinium cation. Crystallization from ethanol affords the title compound tris(4-carboxypyridinium) hydrogensulfate sulfate monohydrate, 3C6H6NO2+·HSO4−·SO42−·H2O or [(H2ina)3(HSO4)(SO4)(H2O)]. This solid contains 11 classical hydrogen bonds of very different flavour and nonclassical C-H...O contacts. All N-H and O-H donors find at least one acceptor within a suitable distance range, with one of the three pyridinium H atoms engaged in bifurcated N-H...O hydrogen bonds. The shortest hydrogen-bonding O...O distance is subtended by hydrogensulfate and sulfate anions, viz. 2.4752 (19) Å, and represents one of the shortest hydrogen bonds ever reported between these residues. [ABSTRACT FROM AUTHOR]