The ID10 beamline of the SESAME (Synchrotron-light for Experimental Science and Applications in the Middle East) synchrotron light source in Jordan was inaugurated in June 2023 and is now open to scientific users. The beamline, which was designed and installed within the European Horizon 2020 project BEAmline for Tomography at SESAME (BEATS), provides full-field X-ray radiography and microtomography imaging with monochromatic or polychromatic X-rays up to photon energies of 100 keV. The photon source generated by a 2.9 T wavelength shifter with variable gap, and a double-multilayer monochromator system allow versatile application for experiments requiring either an X-ray beam with high intensity and flux, and/or a partially spatial coherent beam for phase-contrast applications. Sample manipulation and X-ray detection systems are designed to allow scanning samples with different size, weight and material, providing image voxel sizes from 13 µm down to 0.33 µm. A state-of-the-art computing infrastructure for data collection, three-dimensional (3D) image reconstruction and data analysis allows the visualization and exploration of results online within a few seconds from the completion of a scan. Insights from 3D X-ray imaging are key to the investigation of specimens from archaeology and cultural heritage, biology and health sciences, materials science and engineering, earth, environmental sciences and more. Microtomography scans and preliminary results obtained at the beamline demonstrate that the new beamline ID10-BEATS expands significantly the range of scientific applications that can be targeted at SESAME.

The simulation of EXAFS spectra of thin films via ab initio methods is discussed. The procedure for producing the spectra is presented as well as an application to a two-dimensional material (WSe2) where the effectiveness of this method in reproducing the spectrum and the linear dichroic response is shown. A series of further examples in which the method has been employed for the structural determination of materials are given.

The Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL) operates hard X-ray and soft X-ray beamlines for conducting scientific experiments providing intense ultrashort X-ray pulses based on the self-amplified spontaneous emission (SASE) process. The X-ray free-electron laser is characterized by strong pulse-to-pulse fluctuations resulting from the SASE process. Therefore, online photon diagnostics are very important for rigorous measurements. The concept of photo-absorption and emission using solid materials is seldom considered in soft X-ray beamline diagnostics. Instead, gas monitoring detectors, which utilize the photo-ionization of noble gas, are employed for monitoring the beam intensity. To track the beam position at the soft X-ray beamline in addition to those intensity monitors, an X-ray ionization beam position monitor (XIBPM) has been developed and characterized at the soft X-ray beamline of PAL-XFEL. The XIBPM utilizes ionization of either the residual gas in an ultra-high-vacuum environment or injected krypton gas, along with a microchannel plate with phosphor. The XIBPM was tested separately for monitoring horizontal and vertical beam positions, confirming the feasibility of tracking relative changes in beam position both on average and down to single-shot measurements. This paper presents the basic structure and test results of the newly developed non-invasive XIBPM.

The diagnostics of X-ray beam properties has a critical importance at the European X-ray Free-Electron Laser facility. Besides existing diagnostic components, utilization of a diamond sensor was proposed to achieve radiation-hard, non-invasive beam position and pulse energy measurements for hard X-rays. In particular, with very hard X-rays, diamond-based sensors become a useful complement to gas-based devices which lose sensitivity due to significantly reduced gas cross-sections. The measurements presented in this work were performed with diamond sensors consisting of an electronic-grade single-crystal chemical-vapor-deposition diamond with position-sensitive resistive electrodes in a duo-lateral configuration. The results show that the diamond sensor delivers pulse-resolved X-ray beam position data at 2.25 MHz with an uncertainty of less than 1% of the beam size. To our knowledge this is the first demonstration of pulse-resolved position measurements at the MHz rate using a transmissive diamond sensor at a free-electron laser facility. It can therefore be a valuable tool for X-ray free-electron lasers, especially for high-repetition-rate machines, enabling applications such as beam-based alignment and intra-pulse-train position feedback.

The paper considers the possibility of using the diamond-silicon carbide composite Skeleton® with a technological coating of polycrystalline silicon as a substrate for X-ray mirrors used with powerful synchrotron radiation sources (third+ and fourth generation). Samples were studied after polishing to provide the following surface parameters: root-mean-square flatness ≃ 50 nm, micro-roughness on the frame 2 µm × 2 µm σ ≃ 0.15 nm. The heat capacity, thermal conductivity and coefficient of linear thermal expansion were investigated. For comparison, a monocrystalline silicon sample was studied under the same conditions using the same methods. The value of the coefficient of linear thermal expansion turned out to be higher than that of monocrystalline silicon and amounted to 4.3 × 10−6 K−1, and the values of thermal conductivity (5.0 W cm−1 K−1) and heat capacity (1.2 J K−1 g−1) also exceeded the values for Si. Thermally induced deformations of both Skeleton® and monocrystalline silicon samples under irradiation with a CO2 laser beam have also been experimentally studied. Taking into account the obtained thermophysical constants, the calculation of thermally induced deformation under irradiation with hard (20 keV) X-rays showed almost three times less deformation of the Skeleton® sample than of the monocrystalline silicon sample.

Advances in physics have been significantly driven by state-of-the-art technology, and in photonics and X-ray science this calls for the ability to manipulate the characteristics of optical beams. Orbital angular momentum (OAM) beams hold substantial promise in various domains such as ultra-high-capacity optical communication, rotating body detection, optical tweezers, laser processing, super-resolution imaging etc. Hence, the advancement of OAM beam-generation technology and the enhancement of its technical proficiency and characterization capabilities are of paramount importance. These endeavours will not only facilitate the use of OAM beams in the aforementioned sectors but also extend the scope of applications in diverse fields related to OAM beams. At the FERMI Free-Electron Laser (Trieste, Italy), OAM beams are generated either by tailoring the emission process on the undulator side or, in most cases, by coupling a spiral zone plate (SZP) in tandem with the refocusing Kirkpatrick–Baez active optic system (KAOS). To provide a robust and reproducible workflow to users, a Hartmann wavefront sensor (WFS) is used for both optics tuning and beam characterization. KAOS is capable of delivering both tightly focused and broad spots, with independent control over vertical and horizontal magnification. This study explores a novel non-conventional `near collimation' operational mode aimed at generating beams with OAM that employs the use of a lithographically manufactured SZP to achieve this goal. The article evaluates the mirror's performance through Hartmann wavefront sensing, offers a discussion of data analysis methodologies, and provides a quantitative analysis of these results with ptychographic reconstructions.

The ability to freely control the polarization of X-rays enables measurement techniques relying on circular or linear dichroism, which have become indispensable tools for characterizing the properties of chiral molecules or magnetic structures. Therefore, the demand for polarization control in X-ray free-electron lasers is increasing to enable polarization-sensitive dynamical studies on ultrafast time scales. The soft X-ray branch Athos of SwissFEL was designed with the aim of providing freely adjustable and arbitrary polarization by building its undulator solely from modules of the novel Apple X type. In this paper, the magnetic model of the linear inclined and circular Apple X polarization schemes are studied. The polarization is characterized by measuring the angular electron emission distributions of helium for various polarizations using cold target recoil ion momentum spectroscopy. The generation of fully linear polarized light of arbitrary angle, as well as elliptical polarizations of varying degree, are demonstrated.

Full-field transmission X-ray microscopy has been recently implemented at the hard X-ray ROCK–SOLEIL quick-EXAFS beamline, adding micrometre spatial resolution to the second time resolution characterizing the beamline. Benefiting from a beam size versatility due to the beamline focusing optics, full-field hyperspectral XANES imaging has been successfully used at the Fe K-edge for monitoring the pressure-induced spin transition of a 150 µm × 150 µm Fe(o-phen)2(NCS)2 single crystal and the charge of millimetre-sized LiFePO4 battery electrodes. Hyperspectral imaging over 2000 eV has been reported for the simultaneous monitoring of Fe and Cu speciation changes during activation of a FeCu bimetallic catalyst along a millimetre-sized catalyst bed. Strategies of data acquisition and post-data analysis using Jupyter notebooks and multivariate data analysis are presented, and the gain obtained using full-field hyperspectral quick-EXAFS imaging for studies of functional materials under process conditions in comparison with macroscopic information obtained by non-spatially resolved quick-EXAFS techniques is discussed.

Small-angle-scattering tensor tomography is a technique for studying anisotropic nanostructures of millimetre-sized samples in a volume-resolved manner. It requires the acquisition of data through repeated tomographic rotations about an axis which is subjected to a series of tilts. The tilt that can be achieved with a typical setup is geometrically constrained, which leads to limits in the set of directions from which the different parts of the reciprocal space map can be probed. Here, we characterize the impact of this limitation on reconstructions in terms of the missing wedge problem of tomography, by treating the problem of tensor tomography as the reconstruction of a three-dimensional field of functions on the unit sphere, represented by a grid of Gaussian radial basis functions. We then devise an acquisition scheme to obtain complete data by remounting the sample, which we apply to a sample of human trabecular bone. Performing tensor tomographic reconstructions of limited data sets as well as the complete data set, we further investigate and validate the missing wedge problem by investigating reconstruction errors due to data incompleteness across both real and reciprocal space. Finally, we carry out an analysis of orientations and derived scalar quantities, to quantify the impact of this missing wedge problem on a typical tensor tomographic analysis. We conclude that the effects of data incompleteness are consistent with the predicted impact of the missing wedge problem, and that the impact on tensor tomographic analysis is appreciable but limited, especially if precautions are taken. In particular, there is only limited impact on the means and relative anisotropies of the reconstructed reciprocal space maps.

A state-of-the-art multilayer deposition system with a 4200 mm-long linear substrate translator housed within an ultra-high vacuum chamber has been developed. This instrument is engineered to produce single and multilayer coatings, accommodating mirrors up to 2000 mm in length through the utilization of eight rectangular cathodes. To ensure the quality and reliability of the coatings, the system incorporates various diagnostic tools for in situ thickness uniformity and stress measurement. Furthermore, the system features an annealing process capable of heating up to 700°C within the load-lock chamber. The entire operation, including pump down, deposition and venting processes, is automated through user-friendly software. In addition, all essential log data, power of sputtering source, working pressure and motion positions are automatically stored for comprehensive data analysis. Preliminary commissioning results demonstrate excellent lateral film thickness uniformity, achieving 0.26% along the translation direction over 1500 mm in dynamic mode. The multilayer deposition system is poised for use in fabricating periodic, lateral-graded and depth-graded multilayers, specifically catering to the beamlines for diverse scientific applications at Diamond Light Source.

The title compound, [RuCl2(C25H22P2)2] or [RuCl2(dppm)2] (dppm = bis­(di­phenyl­phosphan­yl)methane, C25H22P2) crystallizes as two half-mol­ecules (completed by inversion symmetry) in space group Poverline{1} (Z = 2), with the RuII atoms occupying inversion centers at 0,0,0 and 1/2, 1/2, 1/2, respectively. The bidentate phosphane ligands occupy equatorial positions while the chlorido ligands complete the distorted octa­hedral coordination spheres at axial positions. The bite angles of the phosphane chelates are similar for the two mol­ecules [(P—Ru—P)avg. = 71.1°], while there are significant differences in the twisting of the methyl­ene backbone, with a distance of the methyl­ene C atom from the RuP4 plane of 0.659 (2) and 0.299 (3) Å, respectively, and also for the phenyl substituents for both mol­ecules due to variations in weak C—H⋯Cl inter­actions.

A second crystalline modification of the title compound, C12H19N3S [common name: cis-jasmone thio­semicarbazone] was crystallized from tetra­hydro­furane at room temperature. There is one crystallographic independent mol­ecule in the asymmetric unit, showing disorder in the cis-jasmone chain [site-occupancy ratio = 0.590 (14):0.410 (14)]. The thio­semicarbazone entity is approximately planar, with the maximum deviation from the mean plane through the N/N/C/S/N atoms being 0.0463 (14) Å [r.m.s.d. = 0.0324 Å], while for the five-membered ring of the jasmone fragment, the maximum deviation from the mean plane through the carbon atoms amounts to 0.0465 (15) Å [r.m.s.d. = 0.0338 Å]. The mol­ecule is not planar due to the dihedral angle between these two fragments, which is 8.93 (1)°, and due to the sp3-hybridized carbon atoms in the jasmone fragment chain. In the crystal, the mol­ecules are connected by N—H⋯S and C—H⋯S inter­actions, with graph-set motifs R22(8) and R21(7), building mono-periodic hydrogen-bonded ribbons along [010]. A Hirshfeld surface analysis indicates that the major contributions for the crystal cohesion are H⋯H (67.8%), H⋯S/S⋯H (15.0%), H⋯C/C⋯H (8.5%) and H⋯N/N⋯H (5.6%) [only non-disordered atoms and those with the highest s.o.f. were considered]. This work reports the second crystalline modification of the cis-jasmone thio­semicarbazone structure, the first one being published recently [Orsoni et al. (2020). Int. J. Mol. Sci. 21, 8681–8697] with the crystals obtained in ethanol at 273 K.

The structure of the title solvated porphyrin, C56H38N8O2·C6H14, is reported. Two porphyrin mol­ecules, one ordered and one disordered n-hexane solvate mol­ecules are present in its asymmetric unit. The porphyrin macrocycle shows a characteristic saddle-shaped distortion, and the maximum deviation from the mean plane for non-hydrogen atoms is 0.48 Å. N—H⋯N, N—H⋯O, and C—H⋯O hydrogen bonds, as well as π–π inter­actions, are observed in the crystal structure.

In the title complex, [Ni(C19H13N5)2](CF3SO3)2·(CH3CH2)2O, the central NiII atom is sixfold coordinated by three nitro­gen atoms of each 2,6-bis­(2-benzimidazol­yl)pyridine ligand in a distorted octa­hedral geometry with two tri­fluoro­methane­sulfonate ions and a mol­ecule of diethyl ether completing the outer coordination sphere of the complex. Hydrogen bonding contributes to the organization of the asymmetric units in columns along the a axis generating a porous supra­molecular structure. The structure was refined as a two-component twin with a refined BASF value of 0.4104 (13).

The title compound, C16H17BrO2S, crystallizes as the erythro (RR/SS) isomer of a pair of sulfones that were diastereomeric due to chirality of the α-carbon atoms on the sulfone sulfur atom. The structural analysis was pivotal in showing that the 1,3 elimination reactions of these compounds, which lead to substituted stilbenes, occur with inversion at each asymmetric carbon atom. In the crystal, C—H⋯Br and C—H⋯O hydrogen bonds link the mol­ecules into a tri-periodic inter­molecular network.

The title compound, C13H10BrNO2, was obtained by the reaction of 2,5-di­bromo­benzoic acid and aniline. The mol­ecule is twisted with a dihedral angle between the aromatic rings of 45.74 (11)° and an intr­amolecular N—H⋯O hydrogen bond is seen. In the crystal, pairwise O—H⋯O hydrogen bonds generate carb­oxy­lic acid inversion dimers.

In the title compound, C26H18BrN, the dihedral angles between the anthracene ring system and the phenyl rings are 89.51 (14) and 74.03 (15)°. In the extended structure, a weak C—H⋯Br inter­action occurs, which generates [100] chains, but no significant π–π or C—H⋯π inter­actions are observed.

The mol­ecular structure of 2-ferrocenyl-2-[(2-ferrocenylethen­yl)(morpholin-4-yl)meth­yl]-1,3-di­thiol­ane, [Fe2(C5H5)2(C19H21NOS2)] or C29H31Fe2NOS2, has the ferrocenyl fragments in a trans disposition with respect to the vinyl group. One of the methyl­ene groups is disordered over two sites with occupancies of 0.782 (13):0.218 (13). In the crystal, cyclo­penta­dienyl-C—H⋯O(morpholin­yl) inter­actions feature within helical chains parallel to the c-axis direction. The chains are connected by methyl­ene- and cyclo­penta­dienyl-C—H⋯O(cyclo­penta­dien­yl) inter­actions.

In the title salt solvate (systematic name: 8-amino-5-ethyl-6-phenyl­phenanthridin-5-ium benzoate methanol monosolvate), C21H20N3+·C6H5CO2−·CH3OH, two ethidium cations, C21H20N3+, dimerize about a twofold axis through π–π inter­actions [inter-centroid separation = 3.6137 (4) Å]. The benzoate anions are connected through hydrogen bonding with the –NH2 groups of the ethidium cations and the –OH group of the MeOH mol­ecule. The MeOH mol­ecule also accepts a hydrogen bond from the –NH2 group of the ethidium cation. The result is a one-dimensional hydrogen-bonded chain along the b-axis direction.

The cation of the title hydrated salt, C17H17BN3+·I−·H2O, is a di­aza­borinane featuring substitution at the 1, 2, and 3 positions in the nitro­gen–boron six-membered heterocycle. The cation is approximately planar with a dihedral angle between the pyridyl ring and the di­aza­borinane ring system of 5.40 (5)°. In the crystal, the cations stack along [100] in an alternating head-to-tail manner, while the iodide ion and water mol­ecule form one-dimensional hydrogen-bonded chains beside the cation stack. The cation stacks and I−–water chains are crosslinked by N—H⋯I and N—H⋯O hydrogen bonds.

In the title salt, (C8H20N)8[Mo10O34], the [Mo10O34]8− polyanion is located about an inversion centre and can be considered as a β-type octa­molybdate anion to which two additional MoO4 tetra­hedra are linked via common corners. The [Mo10O34]8− polyanions are packed in rows extending parallel to [001] and are connected to the di­butyl­ammonium counter-cations through N—H⋯O hydrogen-bonding inter­actions.

In the title compound, C26H18BrN, the central benzene ring makes dihedral angles with its adjacent anthracene ring system and pendant benzene ring of 87.49 (13) and 62.01 (17)°, respectively. The N—H moiety is sterically blocked from forming a hydrogen bond, but weak C—H⋯π inter­actions occur in the extended structure.

In the crystal structure of the title compound, {[Co(C11H9NSO5)(C10H9N3)]0.5C3H7NO·H2O}n or {[Co(dmtb)(dpa)]·0.5DMF·H2O}n (dmtb2– = 5-[(di­meth­yl­amino)­thioxometh­oxy]-1,3-benzene­dicarboxyl­ate and dpa = 4,4'-di­pyridyl­amine), an assembly of periodic [Co(C11H9NSO5)(C10H9N3)]n layers extending parallel to the bc plane is present. Each layer is constituted by distorted [CoO4N2] octa­hedra, which are connected through the μ2-coordination modes of both dmtb2– and dpa ligands. Occupationally disordered water and di­meth­yl­formamide (DMF) solvent mol­ecules are located in the voids of the network to which they are connected through hydrogen-bonding inter­actions.

The title compound, (C2H10N2)2[(C10H12N2O8)(MoO3)2]·4H2O, which crystallizes in the monoclinic C2/c space group, was obtained by mixing molybdenum oxide, ethyl­enedi­amine and ethyl­enedi­amine­tetra­acetic acid (H4edta) in a 2:4:1 ratio. The complex anion contains two MoO3 units bridged by an edta4− anion. The midpoint of the central C—C bond of the edta4− anion is located on a crystallographic inversion centre. The independent Mo atom is tridentately coordin­ated by a nitro­gen atom and two carboxyl­ate groups of the edta4− ligand, together with the three oxo ligands, producing a distorted octa­hedral coordination environment. In the three-dimensional supra­molecular crystal structure, the dinuclear anions, the organo­ammonium counter-ions and the solvent water mol­ecules are linked by N—H⋯Ow, N—H⋯Oedta and O—H⋯O hydrogen bonds.

Crystals of the title salt, (C8H20N)[Sn(C6H5)3(C2H2O2S)], comprise diisobutyl­ammonium cations and mercapto­acetato­tri­phenyl­stannate(IV) anions. The bidentate binding mode of the mercapto­acetate ligand gives rise to a five-coordinated, ionic tri­phenyl­tin complex with a distorted cis-trigonal–bipyramidal geometry around the tin atom. In the crystal, charge-assisted ammonium-N—H⋯O(carboxyl­ate) hydrogen-bonding connects two cations and two anions into a four-ion aggregate. Two positions were resolved for one of the phenyl rings with the major component having a site occupancy factor of 0.60 (3).

The title compound, C10H8BrN3OS2, a brominated di­thio­carbazate imine deriv­ative, was obtained from the condensation reaction of S-methyl­dithio­carbazate (SMDTC) and 5-bromo­isatin. The essentially planar mol­ecule exhibits a Z configuration, with the di­thio­carbazate and 5-bromo­isatin fragments located on the same sides of the C=N azomethine bond, which allows for the formation of an intra­molecular N—H⋯Ob (b = bromo­isatin) hydrogen bond generating an S(6) ring motif. In the crystal, adjacent mol­ecules are linked by pairs of N—H⋯O hydrogen bonds, forming dimers characterized by an R22(8) loop motif. In the extended structure, mol­ecules are linked into a three-dimensional network by C—H⋯S and C—H⋯Br hydrogen bonds, C—Br⋯S halogen bonds and aromatic π–π stacking.

The title structure, {[Cu(C4H11NO)3][Cu4(CN)6]·[Cu(C4H10NO)2(H2O)]·H2O}n, is made up of diperiodic honeycomb CuICN networks built from [Cu4(CN)6]2− units, together with two independent CuII complexes: six-coord­inate [Cu(CH3CH2CH(NH2)CH2OH)3]2+ cations, and five-coordinate [Cu(CH3CH2CH(NH2)CH2O)2·H2O] neutral species. The two CuII complexes are not covalently bonded to the CuICN networks. Strong O—H⋯O hydrogen bonds link the CuII complexes into pairs and the pairs are hydrogen bonded into chains along the crystallographic b axis via the hydrate water mol­ecule. In addition, O—H⋯(CN) and N—H⋯(CN) hydrogen bonds link the cations to the CuCN network. In the honeycomb polymeric moiety, all bridging cyanido ligands are disordered over two orientations, head-to-tail and tail-to-head, with occupancies for C and N atoms varying for each CN group.

The title compound, [Ir(C15H10N)2(C19H12N4)]PF6·CH3OH, crystallizes in the C2/c space group with one monocationic iridium complex, one hexa­fluorido­phosphate anion, and one methanol solvent mol­ecule of crystallization in the asymmetric unit, all in general positions. The anion and solvent are linked to the iridium complex cation via hydrogen bonding. All bond lengths and angles fall into expected ranges compared to similar compounds.

The title compound, C2H4BrNO, crystallizes in the monoclinic space group P21/c with one mol­ecule in the asymmetric unit. The almost planar mol­ecules are organized via N—H⋯O hydrogen bonds into a ladder-type network, which can be characterized by the graph sets R22(8) and R24(8). In addition, the mol­ecules are connected by C—H⋯O and C—H⋯Br contacts.

The title compound, C19H15BrN2O, crystallizes with two similar mol­ecules in the asymmetric unit. The extended structure features dimers linked by pairs of N—H⋯O and C—H⋯O hydrogen bonds. The HNCNO moiety of the title compound shows delocalization over the N—C—N part, as evidenced by the similar C—N bond distances.

In the title solvate, C16H18N2O2·CH4O, the dihedral angles between the formamidine backbone and the pendant 2-meth­oxy­phenyl and 2,6-di­methyl­phenyl groups are 14.84 (11) and 81.61 (12)°, respectively. In the crystal, the components are linked by C—H⋯O, O—H⋯O and C—H⋯ π hydrogen bonds, generating a supra­molecular chain that extends along the crystallographic a-axis direction.

The title compound, C14H12O3, is an α-hy­droxy­carb­oxy­lic acid whose ortho­rhom­bic polymorph has been reported earlier [Qiu et al. (2007). Inorg. Chim. Acta, 360, 1819–1824]. The asymmetric unit contains two complete mol­ecules. Classical hydrogen bonds, as well as C—H⋯O contacts, connect the mol­ecules to infinite chains along the crystallographic c-axis direction.

The structures of five ammonium salt forms of mono­sulfonated azo dyes, derivatives of 4-(2-phenyldiazen-1-yl)benzenesulfonate, with the general formula [NH4][O3S(C6H4)NN(C6H3)RR']·XH2O [R = OH, NH2 or N(C2H4OH)2; R' = H or OH] are presented. All form simple layered structures with alternating hydro­phobic (organic) and hydro­philic (cation, solvent and polar groups) layers. To assess for isostructural behaviour of the ammonium cation with M+ ions, the packing of these structures is compared with literature examples. To aid this comparison, the corresponding structures of four potassium salt forms of the mono­sulfonated azo dyes are also presented herein. Of the five ammonium salts it is found that three have isostructural equivalents. In two cases this equivalent is a potassium salt form and in one case it is a rubidium salt form. The isostructurality of ion packing and of unit-cell symmetry and dimensions tolerates cases where the ammonium ions form somewhat different inter­action types with coformer species than do the potassium or rubidium ions. No sodium salt forms are found to be isostructural with any ammonium equivalent. However, similarities in the anion packing within a single hydro­phobic layer are found for a group that consists of the ammonium and rubidium salt forms of one azo anion species and the sodium and silver salt forms of a different azo species.

The crystal structures of three mixed-valence copper cyanide alkanolamine polymers are presented, together with thermogravimetric analysis (TGA) and electron spin resonance (ESR) data. In all three structures, a CuII moiety on a crystallographic center of symmetry is coordinated by two alkanolamines and links two CuICN chains via cyanide bridging groups to form diperiodic sheets. The sheets are linked together by cuprophilic CuI–CuI inter­actions to form a three-dimensional network. In poly[bis­(μ-3-amino­propano­lato)tetra-μ-cyan­ido-dicopper(I)dicopper(II)], [Cu4(CN)4(C3H8NO)2]n, 1, propano­lamine bases have lost their hydroxyl H atoms and coordinate as chelates to two CuII atoms to form a dimeric CuII moiety bridged by the O atoms of the bases with CuII atoms in square-planar coordination. The ESR spectrum is very broad, indicating exchange between the two CuII centers. In poly[bis­(2-amino­pro­pan­ol)tetra-μ-cyanido-dicopper(I)copper(II)], [Cu3(CN)4(C3H9NO)2]n, 2, and poly[bis­(2-amino­ethanol)tetra-μ-cyanido-dicopper(I)copper(II)], [Cu3(CN)4(CH7NO)2]n, 3, a single CuII atom links the CuICN chains together via CN bridges. The chelating alkanolamines are not ionized, and the OH groups form rather long bonds in the axial positions of the octa­hedrally coordinated CuII atoms. The coordination geometries of CuII in 2 and 3 are almost identical, except that the Cu—O distances are longer in 2 than in 3, which may explain their somewhat different ESR spectra. Thermal decom­position in 2 and 3, but not in 1, begins with the loss of HCN(g), and this can be correlated with the presence of OH protons on the ligands in 2 and 3, which are not present in 1.

The receptor ability of diethyl N,N'-(1,3-phenyl­ene)dicarbamate (1) to form host–guest com­plexes with theophylline (TEO) and caffeine (CAF) by mechanochemistry was evaluated. The formation of the 1–TEO com­plex (C12H16N2O4·C7H8N4O2) was preferred and involves the conformational change of one of the ethyl carbamate groups of 1 from the endo conformation to the exo conformation to allow the formation of inter­molecular inter­actions. The formation of an N—H⋯O=C hydrogen bond between 1 and TEO triggers the conformational change of 1. CAF mol­ecules are unable to form an N—H⋯O=C hydrogen bond with 1, making the conformational change and, therefore, the formation of the com­plex impossible. Conformational change and selective binding were monitored by IR spectroscopy, solid-state 13C nuclear magnetic resonance and single-crystal X-ray diffraction. The 1–TEO com­plex was characterized by IR spectroscopy, solid-state 13C nuclear magnetic resonance, powder X-ray diffraction and single-crystal X-ray diffraction.

The well-known copper car­box­yl­ate dimer, with four car­box­yl­ate ligands ex­ten­ding outwards towards the corners of a square, has been employed to generate a series of crystalline com­pounds. In particular, this work centres on the use of the 4-hy­droxy­benzoate anion (Hhba−) and its deprotonated phe­nol­ate form 4-oxidobenzoate (hba2−) to obtain complexes with the general formula [Cu2(Hhba)4–x(hba)xL2–y]x−, where L is an axial coligand (including solvent mol­ecules), x = 0, 1 or 2, and y = 0 or 1. In some cases, short hy­dro­gen bonds result in complexes which may be represented as [Cu2(Hhba)2(H0.5hba)2L2]−. The main focus of the investigation is on the formation of a variety of extended networks through hy­dro­gen bonding and, in some crystals, coordinate bonds when bridging coligands (L) are employed. Crystals of [Cu2(Hhba)4(di­ox­ane)2]·4(di­ox­ane) consist of the expected Cu dimer with the Hhba− anions forming hy­dro­gen bonds to 1,4-di­ox­ane mol­ecules which block network formation. In the case of crystals of com­position [Et4N][Cu2(Hhba)2(H0.5hba)2(CH3OH)(H2O)]·2(di­ox­ane), Li[Cu2(Hhba)2(H0.5hba)2(H2O)2]·3(di­ox­ane)·4H2O and [Cu2(Hhba)2(H0.5hba)2(H0.5DABCO)2]·3CH3OH (DABCO is 1,4-di­aza­bicyclo­[2.2.2]octa­ne), square-grid hy­dro­gen-bonded networks are generated in which the complex serves as one type of 4-con­necting node, whilst a second 4-con­necting node is a hy­dro­gen-bonding motif assembled from four phenol/phenolate groups. Another two-dimensional (2D) network based upon a related square-grid structure is formed in the case of [Et4N]2[Cu2(Hhba)2(hba)2(di­ox­ane)2][Cu2(Hhba)4(di­ox­ane)(H2O)]·CH3OH. In [Cu2(Hhba)4(H2O)2]·2(Et4NNO3), a square-grid structure is again apparent, but, in this case, a pair of nitrate anions, along with four phenolic groups and a pair of water mol­ecules, combine to form a second type of 4-con­necting node. When 1,8-bis­(di­methyl­amino)­naphthalene (bdn, `proton sponge') is used as a base, another square-grid network is generated, i.e. [Hbdn]2[Cu2(Hhba)2(hba)2(H2O)2]·3(di­ox­ane)·H2O, but with only the copper dimer complex serving as a 4-con­necting node. Complex three-dimensional networks are formed in [Cu2(Hhba)4(O-bipy)]·H2O and [Cu2(Hhba)4(O-bipy)2]·2(di­ox­ane), where the potentially bridging 4,4'-bi­pyridine N,N'-dioxide (O-bipy) ligand is employed. Rare cases of mixed car­box­yl­ate copper dimer complexes were obtained in the cases of [Cu2(Hhba)3(OAc)(di­ox­ane)]·3.5(di­ox­ane) and [Cu2(Hhba)2(OAc)2(DABCO)2]·10(di­ox­ane), with each structure possessing a 2D network structure. The final com­pound re­por­ted is a simple hy­dro­gen-bonded chain of com­position (H0.5DABCO)(H1.5hba), formed from the reaction of H2hba and DABCO.

Using a 1:1 cocrystal of (E)-N-(3,4-di­fluoro­phen­yl)-1-(pyridin-4-yl)methanimine with acetic acid, C12H8F2N2·C2H4O2, we investigate the influence of F atoms introduced to the aromatic ring on promoting π–π inter­actions. The cocrystal crystallizes in the triclinic space group P1. Through crystallographic analysis and com­putational studies, we reveal the mol­ecular arrangement within this co­crystal, demonstrating the presence of hydrogen bonding between the acetic acid mol­ecule and the pyridyl group, along with π–π inter­actions between the aromatic rings. Our findings highlight the importance of F atoms in promoting π–π inter­actions without necessitating full halogenation of the aromatic ring.

3D electron diffraction (3D ED), or microcrystal electron diffraction (MicroED), has become an alternative technique for determining the high-resolution crystal structures of compounds from sub-micron-sized crystals. Here, we considered l-alanine, α-glycine and urea, which are known to form good-quality crystals, and collected high-resolution 3D ED data on our in-house TEM instrument. In this study, we present a comparison of independent atom model (IAM) and transferable aspherical atom model (TAAM) kinematical refinement against experimental and simulated data. TAAM refinement on both experimental and simulated data clearly improves the model fitting statistics (R factors and residual electrostatic potential) compared to IAM refinement. This shows that TAAM better represents the experimental electrostatic potential of organic crystals than IAM. Furthermore, we compared the geometrical parameters and atomic displacement parameters (ADPs) resulting from the experimental refinements with the simulated refinements, with the periodic density functional theory (DFT) calculations and with published X-ray and neutron crystal structures. The TAAM refinements on the 3D ED data did not improve the accuracy of the bond lengths between the non-H atoms. The experimental 3D ED data provided more accurate H-atom positions than the IAM refinements on the X-ray diffraction data. The IAM refinements against 3D ED data had a tendency to lead to slightly longer X—H bond lengths than TAAM, but the difference was statistically insignificant. Atomic displacement parameters were too large by tens of percent for l-alanine and α-glycine. Most probably, other unmodelled effects were causing this behaviour, such as radiation damage or dynamical scattering.

The salt ammonium 2-am­ino­mal­on­ate (systematic name: ammonium 2-aza­niumyl­propane­dioate), NH4+·C3H4NO4−, was synthesized in diethyl ether from the starting materials malonic acid, ammonia and bromine. The salt was recrystallized from water as colourless blocks. In the solid state, intra­molecular medium–strong N—H⋯O, weak C—H⋯O and weak C—H⋯N hydrogen bonds build a three-dimensional network.

The synthesis, crystal structure and magnetic properties of an ox­am­ate-con­taining erbium(III) com­plex, namely, tetra­butyl­ammonium aqua­[N-(2,4,6-tri­methyl­phen­yl)oxamato]erbium(III)–di­methyl sulfoxide–water (1/3/1.5), (C16H36N)[Er(C11H12NO3)4(H2O)]·3C2H6OS·1.5H2O or n-Bu4N[Er(Htmpa)4(H2O)]·3DMSO·1.5H2O (1), are reported. The crystal structure of 1 reveals the occurrence of an erbium(III) ion, which is surrounded by four N-phenyl-substituted ox­am­ate ligands and one water mol­ecule in a nine-coordinated environment, together with one tetra­butyl­ammonium cation acting as a counter-ion, and one water and three dimethyl sulfoxide (DMSO) mol­ecules of crystallization. Variable-temperature static (dc) and dynamic (ac) magnetic mea­sure­ments were carried out for this mononuclear com­plex, revealing that it behaves as a field-induced single-ion magnet (SIM) below 5.0 K.

The title compound, 3-[(benzo-1,3-dioxol-5-yl)amino]-4-meth­oxy­cyclo­but-3-ene-1,2-dione, C12H9NO5 (3), is a precursor to an anti­mycobacterial squaramide. Block-shaped crystals of a monoclinic form (3-I, space group P21/c, Z = 8, Z' = 2) and needle-shaped crystals of a triclinic form (3-II, space group P-1, Z = 4, Z' = 2) were found to crystallize concomitantly. In both crystal forms, R22(10) dimers assemble through N—H⋯O=C hydrogen bonds. These dimers are formed from crystallographically unique mol­ecules in 3-I, but exhibit crystallographic Ci symmetry in 3-II. Twinning by pseudomerohedry was encountered in the crystals of 3-II. The conformations of 3 in the solid forms 3-I and 3-II are different from one another but are similar for the unique mol­ecules in each polymorph. Density functional theory (DFT) calculations on the free mol­ecule of 3 indicate that a nearly planar conformation is preferred.

The incommensurately modulated structure of (2S,3S)-2-amino-3-hy­droxy-3-methyl-4-phen­oxy­butanoic acid dihydrate (C11H15NO4·2H2O or I·2H2O) is described in the (3+1)-dimensional superspace group P212121(0β0)000 (β = 0.357). The loss of the three-dimensional periodicity is ascribed to the occupational modulation of one positionally disordered solvent water mol­ecule, where the two positions are related by a small translation [ca 0.666 (9) Å] and ∼168 (5)° rotation about one of its O—H bonds, with an average 0.624 (3):0.376 (3) occupancy ratio. The occupational modulation of this mol­ecule arises due to the com­petition between the different hy­dro­gen-bonding motifs associated with each position. The structure can be very well refined in the average approximation (all satellite reflections disregarded) in the space group P212121, with the water mol­ecule refined as disordered over two positions in a 0.625 (16):0.375 (16) ratio. The refinement in the commensurate threefold supercell approximation in the space group P1121 is also of high quality, with the six corresponding water mol­ecules exhibiting three different occupancy ratios averaging 0.635:0.365.

It is well known that Hirshfeld surfaces provide an easy and straightforward way of analysing inter­molecular inter­actions in the crystal environment. The use of atomic Hirshfeld surfaces has also demonstrated that such surfaces carry information related to chemical bonds which allow a deeper evaluation of the structures. Here we briefly summarize the approach of atomic Hirshfeld surfaces while further evaluating the kind of information that can be retrieved from them. We show that the analysis of the metal-centre Hirshfeld surfaces from structures refined via Hirshfeld Atom Refinement (HAR) allow accurate evaluation of contacts of type M⋯H, and that such contacts can be related to the overall shape of the surfaces. The com­pounds analysed were tetra­aqua­bis­(3-carb­oxy­propionato)metal(II), [M(C4H3O4)2(H2O)4], for metal(II)/M = manganese/Mn, cobalt/Co, nickel/Ni and zinc/Zn. We also evaluate the sensitivity of the surfaces by an investigation of seemingly flat surfaces through analysis of the curvature functions in the direction of C—C bonds. The obtained values not only demonstrate variations in curvature but also show a correlation with the hybridization of the C atoms involved in the bond.

Over the last three decades, the technology that makes it possible to follow chemical processes in the solid state in real time has grown enormously. These studies have important implications for the design of new functional materials for applications in optoelectronics and sensors. Light–matter inter­actions are of particular importance, and photocrystallography has proved to be an important tool for studying these inter­actions. In this technique, the three-dimensional structures of light-activated mol­ecules, in their excited states, are determined using single-crystal X-ray crystallography. With advances in the design of high-power lasers, pulsed LEDs and time-gated X-ray detectors, the increased availability of synchrotron facilities, and most recently, the development of XFELs, it is now possible to determine the structures of mol­ecules with lifetimes ranging from minutes down to picoseconds, within a single crystal, using the photocrystallographic technique. This review discusses the procedures for conducting successful photocrystallographic studies and outlines the different methodologies that have been developed to study structures with specific lifetime ranges. The com­plexity of the methods required increases considerably as the lifetime of the excited state shortens. The discussion is supported by examples of successful photocrystallographic studies across a range of timescales and emphasises the importance of the use of com­plementary analytical techniques in order to understand the solid-state processes fully.

The crystal structures of two coordination com­pounds, (acetato-κO)(2,2'-bi­py­ri­dine-κ2N,N')(1,10-phenanthroline-κ2N,N')copper(II) acetate hexa­hydrate, [Cu(C2H3O2)(C10H8N2)(C12H8N2)](C2H3O2)·6H2O or [Cu(bipy)(phen)Ac]Ac·6H2O, and (acetato-κO)bis­(2,2'-bi­py­ri­dine-κ2N,N')copper(II) acetate–acetic acid–water (1/1/3), [Cu(C2H3O2)(C10H8N2)2](C2H3O2)·C2H4O2·3H2O or [Cu(bipy)2Ac]Ac·HAc·3H2O, are reported and com­pared with the previously published structure of [Cu(phen)2Ac]Ac·7H2O (phen is 1,10-phenanthroline, bipy for 2,2'-bi­py­ri­dine, ac is acetate and Hac is acetic acid). The geometry around the metal centre is penta­coordinated, but highly distorted in all three cases. The coordination number and the geometric distortion are both discussed in detail, and all com­plexes belong to the space group Poverline{1}. The analysis of the geometric parameters and the Hirshfeld surface properties dnorm and curvedness provide information about the metal–ligand inter­actions in these com­plexes and allow com­parison with similar systems.

Starting from (p-tolyl­sulfin­yl)fer­ro­cene (1), a mixture of the complete series [CpFe{C5H5–n(SOTol-p)n}] (n = 2–4) (2–4) in all regioisomers was obtained. After chromatographic separation, crystals of 1,2-bis­[(4-methyl­benzene)­sulfin­yl]fer­ro­cene, 2a, and 1,3-bis­[(4-methyl­benzene)­sulfin­yl]fer­ro­cene, 2b, both [Fe(C5H5)(C19H17O2S2)], as well as of 1,2,3-tris­[(4-methyl­benzene)­sulfin­yl]fer­ro­cene, [Fe(C5H5)(C26H23O3S3)], 3a, and 1,2,3,4-tetra­kis­[(4-methyl­benzene)­sul­fin­yl]fer­ro­cene ethyl acetate 0.75-solvate, [Fe(C5H5)(C33H29O4S4)]·0.75C4H8O2, 4, could be isolated. Their mol­ecular and crystal structures are compared with each other and also with the so far un­reported structures of related 1,2-bis­(phenyl­sulfan­yl)fer­ro­cene, [Fe(C5H5)(C17H13S2)], 5, and 1,2,3,4-tetra­kis­(phenyl­sulfan­yl)fer­ro­cene, [Fe(C5H5)(C29H21S4)], 6. In all the sulfinyl structures, the O atoms of the S=O groups are in equatorial positions, except for that in tetrasubstituted 4. All the arene rings of these com­pounds (except for one ring in 4) are in axial positions directed away from the Fe atom, mostly in a near perpendicular orientation with respect to the plane of the cyclo­penta­di­en­yl ring. The main inter­molecular inter­actions in the crystals are C—H⋯H—C, C—H⋯π and C—H⋯O, while C—H⋯S inter­actions are much less important, except for tetra­sul­fan­yl com­pound 6. π–π inter­actions (intra­molecular) are only important in com­pound 3a. Hirshfeld analysis shows that dispersion terms are dominant for the inter­action energies of all six com­pounds. In general, the calculated total inter­action energies increase with increasing number of substituents and are higher for the sulfinyl than for the sul­fan­yl groups.

Density modification is a standard step to provide a route for routine structure solution by any experimental phasing method, with single-wavelength or multi-wavelength anomalous diffraction being the most popular methods, as well as to extend fragments or incomplete models into a full solution. The effect of density modification on the starting maps from either source is illustrated in the case of SHELXE. The different modes in which the program can run are reviewed; these include less well known uses such as reading external phase values and weights or phase distributions encoded in Hendrickson–Lattman coefficients. Typically in SHELXE, initial phases are calculated from experimental data, from a partial model or map, or from a combination of both sources. The initial phase set is improved and extended by density modification and, if the resolution of the data and the type of structure permits, polyalanine tracing. As a feature to systematically eliminate model bias from phases derived from predicted models, the trace can be set to exclude the area occupied by the starting model. The trace now includes an extension into the gamma position or hydrophobic and aromatic side chains if a sequence is provided, which is performed in every tracing cycle. Once a correlation coefficient of over 30% between the structure factors calculated from such a trace and the native data indicates that the structure has been solved, the sequence is docked in all model-building cycles and side chains are fitted if the map supports it. The extensions to the tracing algorithm brought in to provide a complete model are discussed. The improvement in phasing performance is assessed using a set of tests.

This article describes the High-Pressure Freezing Laboratory for Macromolecular Crystallography (HPMX) at the ESRF, and highlights new and complementary research opportunities that can be explored using this facility. The laboratory is dedicated to investigating interactions between macromolecules and gases in crystallo, and finds applications in many fields of research, including fundamental biology, biochemistry, and environmental and medical science. At present, the HPMX laboratory offers the use of different high-pressure cells adapted for helium, argon, krypton, xenon, nitrogen, oxygen, carbon dioxide and methane. Important scientific applications of high pressure to macromolecules at the HPMX include noble-gas derivatization of crystals to detect and map the internal architecture of proteins (pockets, tunnels and channels) that allows the storage and diffusion of ligands or substrates/products, the investigation of the catalytic mechanisms of gas-employing enzymes (using oxygen, carbon dioxide or methane as substrates) to possibly decipher intermediates, and studies of the conformational fluctuations or structure modifications that are necessary for proteins to function. Additionally, cryo-cooling protein crystals under high pressure (helium or argon at 2000 bar) enables the addition of cryo-protectant to be avoided and noble gases can be employed to produce derivatives for structure resolution. The high-pressure systems are designed to process crystals along a well defined pathway in the phase diagram (pressure–temperature) of the gas to cryo-cool the samples according to the three-step `soak-and-freeze method'. Firstly, crystals are soaked in a pressurized pure gas atmosphere (at 294 K) to introduce the gas and facilitate its inter­actions within the macromolecules. Samples are then flash-cooled (at 100 K) while still under pressure to cryo-trap macromolecule–gas complexation states or pressure-induced protein modifications. Finally, the samples are recovered after depressurization at cryo-temperatures. The final section of this publication presents a selection of different typical high-pressure experiments carried out at the HPMX, showing that this technique has already answered a wide range of scientific questions. It is shown that the use of different gases and pressure conditions can be used to probe various effects, such as mapping the functional internal architectures of enzymes (tunnels in the haloalkane dehalogenase DhaA) and allosteric sites on membrane-protein surfaces, the interaction of non-inert gases with proteins (oxygen in the hydrogenase ReMBH) and pressure-induced structural changes of proteins (tetramer dissociation in urate oxidase). The technique is versatile and the provision of pressure cells and their application at the HPMX is gradually being extended to address new scientific questions.

Over the last decade, the development of time-resolved serial crystallography (TR-SX) at X-ray free-electron lasers (XFELs) and synchrotrons has allowed researchers to study phenomena occurring in proteins on the femtosecond-to-minute timescale, taking advantage of many technical and methodological breakthroughs. Protein crystals of various sizes are presented to the X-ray beam in either a static or a moving medium. Photoactive proteins were naturally the initial systems to be studied in TR-SX experiments using pump–probe schemes, where the pump is a pulse of visible light. Other reaction initiations through small-molecule diffusion are gaining momentum. Here, selected examples of XFEL and synchrotron time-resolved crystallography studies will be used to highlight the specificities of the various instruments and methods with respect to time resolution, and are compared with cryo-trapping studies.