A new scaling program is presented with new features to support multi-sweep workflows and analysis within the DIALS software package.

Structures of the immunodominant protein P46 from M. hyopneumoniae has been determined by X-ray crystallography and it is shown that P46 can bind a diversity of oligosaccharides, particularly xylose, which exhibits a very high affinity for this protein. Structures of a monoclonal antibody, both alone and in complex with P46, that was raised against M. hyopnemoniae cells and specifically recognizes P46 are also reported.

Death-associated protein kinase 1 (DAPK1) was found to form a complex with purpurin and the crystal structure of the complex was determined. Purpurin may be a good lead compound for for the discovery of inhibitors of DAPK1.

The bond-valence method was performed on 51 crystal data sets from nitrogenase proteins, indicating the presence of molybdenum(III) in FeMo cofactors and vanadium(III) with more reduced iron complements in FeV cofactors.

Comparison of the structures of ClpC1-Ecumicin and ClpC1-Rufomycin reveals unique interaction relevant to the mode of action.

The asymmetric unit of the title compound (systematic name: 3,3,8,8-tetra­methyl-1,4,6,9-tetra­oxa-λ4-bora­spiro­[4.4]nonane-2,7-dione tetra­hydrate), C8H12BO6·4H2O, consists of half a bis­(2-methyl­lactato)borate mol­ecule and two water mol­ecules of solvation. In the crystal, O—H⋯O hydrogen bonds link the components into a three-dimensional network.

Single crystals of rubidium tetra­fluorido­bromate(III), RbBrF4, were grown by melting and recrystallizing RbBrF4 from its melt. This is the first determination of the crystal structure of RbBrF4 using single-crystal X-ray diffraction data. We confirmed that the structure contains square-planar [BrF4]− anions and rubidium cations that are coordinated by F atoms in a square-anti­prismatic manner. The compound crystallizes in the KBrF4 structure type. Atomic coordinates and bond lengths and angles were determined with higher precision than in a previous report based on powder X-ray diffraction data [Ivlev et al. (2015). Z. Anorg. Allg. Chem. 641, 2593–2598].

Caesium tetra­fluorido­bromate(III), CsBrF4, was crystallized in form of small blocks by melting and recrystallization. The crystal structure of CsBrF4 was redetermined from single-crystal X-ray diffraction data. In comparison with a previous study based on powder X-ray diffraction data [Ivlev et al. (2013). Z. Anorg. Allg. Chem. 639, 2846–2850], bond lengths and angles were determined with higher precision, and all atoms were refined with anisotropic displacement parameters. It was confirmed that the structure of CsBrF4 contains two square-planar [BrF4]− anions each with point group symmetry mmm, and a caesium cation (site symmetry mm2) that is coordinated by twelve fluorine atoms, forming an anti­cubocta­hedron. CsBrF4 is isotypic with CsAuF4.

The crystal structure of pirfenidone, C12H11NO [alternative name: 5-methyl-1-phenyl­pyridin-2(1H)-one], an active pharmaceutical ingredient (API) approved in Europe and Japan for the treatment of Idiopathic pulmonary fibrosis (IPF), is reported here for the first time. It was crystallized from toluene by the temperature gradient technique, and crystallizes in the chiral monoclinic space group P21. The phenyl and pyridone rings are inclined to each other by 50.30 (11)°. In the crystal, mol­ecules are linked by C–H⋯O hydrogen bonds involving the same acceptor atom, forming undulating layers lying parallel to the ab plane.

The solvated centrosymmmtric title compound, [Li2(C24H34O4P)2(C10H8N2)2]·2C7H8, was formed in the reaction between {Li[(2,6-iPr2C6H3-O)2POO](MeOH)3}(MeOH) and 2,2'-bi­pyridine (bipy) in toluene. The structure has monoclinic (P21/n) symmetry at 120 K and the asymmetric unit consists of half a complex mol­ecule and one mol­ecule of toluene solvent. The diaryl phosphate ligand demonstrates a μ-κO:κO'-bridging coordination mode and the 2,2'-bi­pyridine ligand is chelating to the Li+ cation, generating a distorted tetra­hedral LiN2O2 coordination polyhedron. The complex exhibits a unique dimeric Li2O4P2 core. One isopropyl group is disordered over two orientations in a 0.621 (4):0.379 (4) ratio. In the crystal, weak C—H⋯O and C—H⋯π inter­actions help to consolidate the packing. Catalytic systems based on the title complex and on the closely related complex {Li[(2,6-iPr2C6H3-O)2POO](MeOH)3}(MeOH) display activity in the ring-opening polymerization of ∊-caprolactone and l-dilactide.

The title compound, C21H16N2O2, consists of an imidazolidine unit linked to two phenyl rings and two prop-2-yn-1-yl moieties. The imidazolidine ring is oriented at dihedral angles of 79.10 (5) and 82.61 (5)° with respect to the phenyl rings, while the dihedral angle between the two phenyl rings is 62.06 (5)°. In the crystal, inter­molecular C—HProp⋯OImdzln (Prop = prop-2-yn-1-yl and Imdzln = imidazolidine) hydrogen bonds link the mol­ecules into infinite chains along the b-axis direction. Two weak C—HPhen⋯π inter­actions are also observed. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (43.3%), H⋯C/C⋯H (37.8%) and H⋯O/O⋯H (18.0%) inter­actions. Hydrogen bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that the C—HProp⋯OImdzln hydrogen-bond energy in the crystal is −40.7 kJ mol−1. Density functional theory (DFT) optimized structures at the B3LYP/6–311G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

Typical electroless copper baths (ECBs), which are used to chemically deposit copper on printed circuit boards, consist of an aqueous alkali hydroxide solution, a copper(II) salt, formaldehyde as reducing agent, an l-(+)-tartrate as complexing agent, and a 2,2'-bi­pyridine derivative as stabilizer. Actual speciation and reactivity are, however, largely unknown. Herein, we report on the synthesis and crystal structure of aqua-1κO-bis­(4,4'-dimeth­oxy-2,2'-bi­pyri­dine)-1κ2N,N';2κ2N,N'-[μ-(2R,3R)-2,3-dioxidosuccinato-1κ2O1,O2:2κ2O3,O4]dicopper(II) octa­hydrate, [Cu2(C12H12N2O2)2(C4H2O6)(H2O)]·8H2O, from an ECB mock-up. The title compound crystallizes in the Sohncke group P21 with one chiral dinuclear complex and eight mol­ecules of hydrate water in the asymmetric unit. The expected retention of the tartrato ligand's absolute configuration was confirmed via determination of the absolute structure. The complex mol­ecules exhibit an ansa-like structure with two planar, nearly parallel bi­pyridine ligands, each bound to a copper atom that is connected to the other by a bridging tartrato `handle'. The complex and water mol­ecules give rise to a layered supra­molecular structure dominated by alternating π stacks and hydrogen bonds. The understanding of structures ex situ is a first step on the way to prolonged stability and improved coating behavior of ECBs.

The coordination of the ligands with respect to the central atom in the complex bromido­tricarbon­yl[diphen­yl(pyridin-2-yl)phosphane-κ2N,P]rhenium(I) chloro­form disolvate, [ReBr(C17H14NP)(CO)3]·2CHCl3 or [κ2-P,N-{(C6H5)2(C5H5N)P}Re(CO)3Br]·2CHCl3, (I·2CHCl3), is best described as a distorted octa­hedron with three carbonyls in a facial conformation, a bromide atom, and a biting P,N-di­phenyl­pyridyl­phosphine ligand. Hirshfeld surface analysis shows that C—Cl⋯H inter­actions contribute 26%, the distance of these inter­actions are between 2.895 and 3.213 Å. The reaction between I and piperidine (C5H11N) at 313 K in di­chloro­methane leads to the partial decoord­ination of the pyridyl­phosphine ligand, whose pyridyl group is replaced by a piperidine mol­ecule, and the complex bromido­tricarbon­yl[diphen­yl(pyridin-2-yl)phosphane-κP](piperidine-κN)rhenium(I), [ReBr(C5H11N)(C17H14NP)(CO)3] or [P-{(C6H5)2(C5H5N)P}(C5H11N)Re(CO)3Br] (II). The mol­ecule has an intra­molecular N—H⋯N hydrogen bond between the non-coordinated pyridyl nitro­gen atom and the amine hydrogen atom from piperidine with D⋯A = 2.992 (9) Å. Thermogravimetry shows that I·2CHCl3 losses 28% of its mass in a narrow range between 318 and 333 K, which is completely consistent with two solvating chloro­form mol­ecules very weakly bonded to I. The remaining I is stable at least to 573 K. In contrast, II seems to lose solvent and piperidine (12% of mass) between 427 and 463 K, while the additional 33% loss from this last temperature to 573 K corresponds to the release of 2-pyridyl­phosphine. The contribution to the scattering from highly disordered solvent mol­ecules in II was removed with the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9-18] in PLATON. The stated crystal data for Mr, μ etc. do not take this solvent into account.

The title tetra­nuclear copper complex, [Cu4Cl6O(C6H9N3O3)4] or [Cu4Cl6O­(MET)4] [MET is 1-(2-hy­droxy­eth­yl)-2-methyl-5-nitro-1H-imidazole or metronidazole], contains a tetra­hedral arrangement of copper(II) ions. Each copper atom is also linked to the other three copper atoms in the tetra­hedron via bridging chloride ions. A fifth coordination position on each metal atom is occupied by a nitro­gen atom of the monodentate MET ligand. The result is a distorted CuCl3NO trigonal–bipyramidal coordination polyhedron with the axial positions occupied by oxygen and nitro­gen atoms. The extended structure displays O—H⋯O hydrogen bonding, as well as unusual short O⋯N inter­actions [2.775 (4) Å] between the nitro groups of adjacent clusters that are oriented perpendicular to each other. The scattering contribution of disordered water and methanol solvent mol­ecules was removed using the SQUEEZE procedure [Spek (2015). Acta Cryst. C71, 9–16] in PLATON [Spek (2009). Acta Cryst. D65, 148–155].

Reductive cyclization of 1,3,5-triphenyl- and 3-(2-meth­oxy­phen­yl)-1,5-di­phenyl­pentane-1,5-diones by zinc in acetic acid medium leads to the formation of 1,2,4-tri­phenyl­cyclo­pentane-1,2-diol [1,2,4-Ph3C5H5-1,2-(OH)2, C23H22O2, (I)] and 4-(2-meth­oxy­phen­yl)-1,2-di­phenyl­cyclo­pentane-1,2-diol [4-(2-MeOC6H4)-1,2-Ph2C5H5-1,2-(OH)2, C24H24O3, (II)]. Their single crystals have been obtained by crystallization from a THF/hexane solvent mixture. Diols (I) and (II) crystallize in ortho­rhom­bic (Pbca) and triclinic (Poverline{1}) space groups, respectively, at 150 K. Their asymmetric units comprise one [in the case of (I)] and three [in the case of (II)] crystallographically independent mol­ecules of the achiral (1R,2S,4r)-diol isomer. Each hydroxyl group is involved in one intra­molecular and one inter­molecular O—H⋯O hydrogen bond, forming one-dimensional chains. Compounds (I) and (II) have been used successfully as precatalyst activators for the ring-opening polymerization of ∊-caprolactone.

The reaction of 2,5-bis­(pyridin-4-yl)-1,3,4-oxa­diazole (4-pox) and thio­cyanate ions, used as co-ligand with nickel salt NiCl2·6H2O, produced the title complex, [Ni(NCS)2(C12H8N4O)2(H2O)2]. The NiII atom is located on an inversion centre and is octa­hedrally coordinated by four N atoms from two ligands and two pseudohalide ions, forming the equatorial plane. The axial positions are occupied by two O atoms of coordinated water mol­ecules. In the crystal, the mol­ecules are linked into a three-dimensional network through strong O—H⋯N hydrogen bonds. Hirshfeld surface analysis was used to investigate the inter­molecular inter­actions in the crystal packing.

This study is an investigation into the crystal structure of the biologically active drug mol­ecule riluzole [RZ, 6-(tri­fluoro­meth­oxy)-1,3-benzo­thia­zol-2-amine], C8H5F3N2OS, and its derivative, the riluzolium chloride salt [RZHCl, 2-amino-6-(tri­fluoro­meth­oxy)-1,3-benzo­thia­zol-3-ium chloride], C8H6F3N2OS+·Cl−. In spite of repeated efforts to crystallize the drug, its crystal structure has not been reported to date, hence the current study provides a method for obtaining crystals of both riluzole and its corresponding salt, riluzolium hydro­chloride. The salt was obtained by grinding HCl with the drug and crystallizing the obtained solid from di­chloro­methane. The crystals of riluzole were obtained in the presence of l-glutamic acid and d-glutamic acid in separate experiments. In the crystal structure of RZHCl, the –OCF3 moiety is perpendicular to the mol­ecular plane containing the riluzolium ion, as can be seen by the torsion angle of 107.4 (3)°. In the case of riluzole, the torsion angles of the four different mol­ecules in the asymmetric unit show that in three cases the tri­fluoro­meth­oxy group is perpendicular to the riluzole mol­ecular plane and only in one mol­ecule does the –OCF3 group lie in the same mol­ecular plane. The crystal structure of riluzole primarily consists of strong N—H⋯N hydrogen bonds along with weak C—H⋯F, C—H⋯S, F⋯F, C⋯C and C⋯S inter­actions, while that of its salt is stabilized by strong [N—H]+⋯Cl− and weak C—H⋯Cl−, N—H⋯S, C—H⋯F, C⋯C, S⋯N and S⋯Cl− inter­actions.

The title compound, C18H16N4O, consists of a 3,6-bis­(pyridin-2-yl)pyridazine moiety linked to a 4-[(prop-2-en-1-yl­oxy)meth­yl] group. The pyridine-2-yl rings are oriented at a dihedral angle of 17.34 (4)° and are rotated slightly out of the plane of the pyridazine ring. In the crystal, C—HPyrd⋯NPyrdz (Pyrd = pyridine and Pyrdz = pyridazine) hydrogen bonds and C—HPrp­oxy⋯π (Prp­oxy = prop-2-en-1-yl­oxy) inter­actions link the mol­ecules, forming deeply corrugated layers approximately parallel to the bc plane and stacked along the a-axis direction. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯H (48.5%), H⋯C/C⋯H (26.0%) and H⋯N/N⋯H (17.1%) contacts, hydrogen bonding and van der Waals inter­actions being the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, the C—HPyrd⋯NPyrdz hydrogen-bond energy is 64.3 kJ mol−1. Density functional theory (DFT) optimized structures at the B3LYP/6–311 G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

The synthesis, crystal structure and structural motif of two thio­phene-based cyano­acrylate derivatives, namely, ethyl (E)-2-cyano-3-(3-methyl­thio­phen-2-yl)acrylate (1), C11H11NO2S, and ethyl (E)-2-cyano-3-(thio­phen-2-yl)acrylate (2), C10H9NO2S, are reported. Derivative 1 crystallized with two independent molecules in the asymmetric unit, and derivative 2 represents a new monoclinic (C2/m) polymorph. The mol­ecular conformations of 1 and the two polymorphs of 2 are very similar, as all non-H atoms are planar except for the methyl of the ethyl groups. The inter­molecular inter­actions and crystal packing of 1 and 2 are described and compared with that of the reported monoclinic (C2/m) polymorph of derivative 2 [Castro Agudelo et al. (2017). Acta Cryst. E73, 1287–1289].

The title compound, C15H12ClNO3, consists of a 1,2-di­hydro­quinoline-4-carb­oxyl­ate unit with 2-chloro­ethyl and propynyl substituents, where the quinoline moiety is almost planar and the propynyl substituent is nearly perpendicular to its mean plane. In the crystal, the mol­ecules form zigzag stacks along the a-axis direction through slightly offset π-stacking inter­actions between inversion-related quinoline moieties which are tied together by inter­molecular C—HPrpn­yl⋯OCarbx and C—HChlethy⋯OCarbx (Prpnyl = propynyl, Carbx = carboxyl­ate and Chlethy = chloro­eth­yl) hydrogen bonds. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (29.9%), H⋯O/O⋯H (21.4%), H⋯C/C⋯ H (19.4%), H⋯Cl/Cl⋯H (16.3%) and C⋯C (8.6%) inter­actions. Hydrogen bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, the C—HPrpn­yl⋯OCarbx and C—HChlethy⋯OCarbx hydrogen bond energies are 67.1 and 61.7 kJ mol−1, respectively. Density functional theory (DFT) optimized structures at the B3LYP/ 6–311 G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

The title mol­ecular salt, (C7H11N2)2[Hg2Cl6], crystallizes with two 4-(di­methyl­amino)­pyridinium cations (A and B) and two half hexa­chlorido­dimercurate(II) anions in the asymmetric unit. The organic cations exhibit essentially the same features with an almost planar pyridyl ring (r.m.s. deviations of 0.0028 and 0.0109 Å), which forms an inclined dihedral angle with the dimethyamino group [3.06 (1) and 1.61 (1)°, respectively]. The di­methyl­amino groups in the two cations are planar, and the C—N bond lengths are shorter than that in 4-(di­methyl­amino)­pyridine. In the crystal, mixed cation–anion layers lying parallel to the (010) plane are formed through N—H⋯Cl hydrogen bonds and adjacent layers are linked by C—H⋯Cl hydrogen bonds, forming a three-dimensional network. The analyses of the calculated Hirshfeld surfaces confirm the relevance of the above inter­molecular inter­actions, but also serve to further differentiate the weaker inter­molecular inter­actions formed by the organic cations and inorganic anions, such as π–π and Cl⋯Cl inter­actions. The powder XRD data confirms the phase purity of the crystalline sample. Furthermore, the vibrational absorption bands were identified by IR spectroscopy and the optical properties were studied by using optical UV–visible absorption spectroscopy.

The title compound, C22H15Cl2NOS, contains 1,4-benzo­thia­zine and 2,4-di­­chloro­benzyl­idene units, where the di­hydro­thia­zine ring adopts a screw-boat conformation. In the crystal, inter­molecular C—HBnz⋯OThz (Bnz = benzene and Thz = thia­zine) hydrogen bonds form corrugated chains extending along the b-axis direction which are connected into layers parallel to the bc plane by inter­molecular C—HMethy⋯SThz (Methy = methyl­ene) hydrogen bonds, en­closing R44(22) ring motifs. Offset π-stacking inter­actions between 2,4-di­­chloro­phenyl rings [centroid–centroid = 3.7701 (8) Å] and π-inter­actions which are associated by C—HBnz⋯π(ring) and C—HDchlphy⋯π(ring) (Dchlphy = 2,4-di­chloro­phen­yl) inter­actions may be effective in the stabilization of the crystal structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (29.1%), H⋯C/C⋯H (27.5%), H⋯Cl/Cl⋯H (20.6%) and O⋯H/H⋯O (7.0%) inter­actions. Hydrogen-bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, the C—HBnz⋯OThz and C—HMethy⋯SThz hydrogen-bond energies are 55.0 and 27.1 kJ mol−1, respectively. Density functional theory (DFT) optimized structures at the B3LYP/6-311G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

The reactions of N-heterocyclic carbene CuI and AgI halides with potassium thio- or seleno­cyanate gave unexpected products. The attempted substitution reaction of bromido­(1,3-dibenzyl-4,5-di­phenyl­imidazol-2-yl­idene)silver (NHC*—Ag—Br) with KSCN yielded bis­[bis­(1,3-dibenzyl-4,5-di­phenyl­imidazol-2-yl­idene)silver(I)] tris­(thio­cyanato)­argentate(I) diethyl ether disolvate, [Ag(C29H24N2)2][Ag(NCS)3]·2C4H10O or [NHC*2Ag]2[Ag(SCN)3]·2Et2O, (1), while reaction with KSeCN led to bis­(μ-1,3-dibenzyl-4,5-diphenyl-2-seleno­imidazole-κ2Se:Se)bis­[bromido­(1,3-dibenzyl-4,5-diphenyl-2-seleno­imid­azole-κSe)silver(I)] di­chloro­methane hexa­solvate, [Ag2Br2(C29H24N2Se)4]·6CH2Cl2 or (NHC*Se)4Ag2Br2·6CH2Cl2, (2), via oxidation of the NHC* fragment to 2-seleno­imidazole. This oxidation was observed again in the reaction of NHC*—Cu—Br with KSeCN, yielding catena-poly[[[(1,3-dibenzyl-4,5-diphenyl-2-seleno­imidazole-κSe)copper(I)]-μ-cyanido-κ2C:N] aceto­nitrile monosolvate], {[Cu(CN)(C29H24N2Se)]·C2H3N}n or NHC*Se—CuCN·CH3CN, (3). Compound (1) represents an organic/inorganic salt with AgI in a linear coordination in each of the two cations and in a trigonal coordination in the anion, accompanied by diethyl ether solvent mol­ecules. The tri-blade boomerang-shaped complex anion [Ag(SCN)3]2− present in (1) is characterized by X-ray diffraction for the first time. Compound (2) comprises an isolated centrosymmetric mol­ecule with AgI in a distorted tetra­hedral BrSe3 coordination, together with di­chloro­methane solvent mol­ecules. Compound (3) exhibits a linear polymeric 1∞[Cu—C≡N—Cu—] chain structure with a seleno­imidazole moiety additionally coordinating to each CuI atom, and completed by aceto­nitrile solvent mol­ecules. Electron densities associated with an additional ether solvent mol­ecule in (1) and two additional di­chloro­methane solvent mol­ecules in (2) were removed with the SQUEEZE procedure [Spek (2015). Acta Cryst. C71, 9–18] in PLATON.

The title com­pound, C22H16N4O2, contains two pyridine rings and one meth­oxy­carbonyl­phenyl group attached to a pyridazine ring which deviates very slightly from planarity. In the crystal, ribbons consisting of inversion-related chains of mol­ecules extending along the a-axis direction are formed by C—HMthy⋯OCarbx (Mthy = methyl and Carbx = carboxyl­ate) hydrogen bonds. The ribbons are connected into layers parallel to the bc plane by C—HBnz⋯π(ring) (Bnz = benzene) inter­actions. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (39.7%), H⋯C/C⋯H (27.5%), H⋯N/N⋯H (15.5%) and O⋯H/H⋯O (11.1%) inter­actions. Hydrogen-bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, C—HMthy⋯OCarbx hydrogen-bond energies are 62.0 and 34.3 kJ mol−1, respectively. Density functional theory (DFT) optimized structures at the B3LYP/6-311G(d,p) level are com­pared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

The asymmetric unit of the title com­pound, catena-poly[[[(perchlorato-κO)copper(II)]-μ-3-(3-carb­oxy­prop­yl)-1,5,8,12-tetra­aza-3-azonia­cyclo­tetra­decane-κ4N1,N5,N8,N12] bis­(per­chlorate)], {[Cu(C13H30N5O2)(ClO4)](ClO4)2}n, (I), consists of a macrocyclic cation, one coordinated per­chlorate anion and two per­chlorate ions as counter-anions. The metal ion is coordinated in a tetra­gonally distorted octa­hedral geometry by the four secondary N atoms of the macrocyclic ligand, the mutually trans O atoms of the per­chlorate anion and the carbonyl O atom of the protonated carb­oxy­lic acid group of a neighbouring cation. The average equatorial Cu—N bond lengths [2.01 (6) Å] are significantly shorter than the axial Cu—O bond lengths [2.379 (8) Å for carboxyl­ate and average 2.62 (7) Å for disordered per­chlorate]. The coordinated macrocyclic ligand in (I) adopts the most energetically favourable trans-III conformation with an equatorial orientation of the substituent at the protonated distal 3-position N atom in a six-membered chelate ring. The coordination of the carb­oxy­lic acid group of the cation to a neighbouring com­plex unit results in the formation of infinite chains running along the b-axis direction, which are cross­linked by N—H⋯O hydrogen bonds between the secondary amine groups of the macrocycle and O atoms of the per­chlorate counter-anions to form sheets lying parallel to the (001) plane. Additionally, the extended structure of (I) is consolidated by numerous intra- and interchain C—H⋯O contacts.

The syntheses and crystal structures of five 2-benzyl­idene-1-benzosuberone [1-benzosuberone is 6,7,8,9-tetra­hydro-5H-benzo[7]annulen-5-one] derivatives, viz. 2-(4-meth­oxy­benzyl­idene)-1-benzosuberone, C19H18O2, (I), 2-(4-eth­oxy­benzyl­idene)-1-benzosuberone, C20H20O2, (II), 2-(4-benzyl­benzyl­idene)-1-benzosuberone, C25H22O2, (III), 2-(4-chloro­benzyl­idene)-1-benzosuberone, C18H15ClO, (IV) and 2-(4-cyano­benzyl­idene)-1-benzosuberone, C19H15NO, (V), are described. The conformations of the benzosuberone fused six- plus seven-membered ring fragments are very similar in each case, but the dihedral angles between the fused benzene ring and the pendant benzene ring differ somewhat, with values of 23.79 (3) for (I), 24.60 (4) for (II), 33.72 (4) for (III), 29.93 (8) for (IV) and 21.81 (7)° for (V). Key features of the packing include pairwise C—H⋯O hydrogen bonds for (II) and (IV), and pairwise C—H⋯N hydrogen bonds for (V), which generate inversion dimers in each case. The packing for (I) and (III) feature C—H⋯O hydrogen bonds, which lead to [010] and [100] chains, respectively. Weak C—H⋯π inter­actions consolidate the structures and weak aromatic π–π stacking is seen in (II) [centroid–centroid separation = 3.8414 (7) Å] and (III) [3.9475 (7) Å]. A polymorph of (I) crystallized from a different solvent has been reported previously [Dimmock et al. (1999) J. Med. Chem. 42, 1358–1366] in the same space group but with a packing motif based on inversion dimers resembling that seen in (IV) in the present study. The Hirshfeld surfaces and fingerprint plots for (I) and its polymorph are com­pared and structural features of the 2-benzyl­idene-1-benzosuberone family of phases are surveyed.

The title compound, [Fe(C44H24N8Cl4)(CN)2][K2(C18H36N2O6)2]·2C4H8O was synthesized and characterized by single-crystal X-ray diffraction as well as FTIR and UV–vis spectroscopy. The central FeII ion is coordinated by four pyrrole N atoms of the porphyrin core and two C atoms of the cyano groups in a slightly distorted octa­hedral coordination environment. The complex mol­ecule crystallizes with two tetra­hydro­furan solvent mol­ecules, one of which was refined as disordered over two sets of sites with refined occupancies of 0.619 (5) and 0.381 (5). It has a distorted porphyrin core with mean absolute core-atom displacements Ca, Cb, Cm and Cav of 0.32 (3), 0.22 (3), 0.56 (2) and 0.37 (14) Å, respectively. The axial Fe—Ccyano bond lengths are 1.991 (2) and 1.988 (2) Å. The average Fe—Np (Np is a porphyrin N atom) bond length is 1.964 (10) Å. One of the O atoms and several C atoms of the 222 moiety [222 = 4,7,13,16,21,24-hexa­oxa-1,10-di­aza­bicyclo­[8.8.8]hexa­cosa­ne] were refined as disordered over two sets of sites with occupancy ratios of 0.739 (6):0.261 (6) and 0.832 (4):0.168 (4). Additional solvent mol­ecules were found to be highly disordered and their contribution to the scattering was removed using the SQUEEZE procedure in PLATON [Spek (2015). Acta Cryst. C71, 9–18], which indicated a solvent cavity of volume 372 Å3 containing approximately 83 electrons. These solvent mol­ecules are not considered in the given chemical formula and other crystal data.

In the title hydrated hybrid compound C14H14N2OS2·H2O, the planar imidazo[1,2-a]pyridine ring system is linked to the 1,3-di­thiol­ane moiety by an enone bridge. The atoms of the C—C bond in the 1,3-di­thiol­ane ring are disordered over two positions with occupancies of 0.579 (14) and 0.421 (14) and both disordered rings adopt a half-chair conformation. The oxygen atom of the enone bridge is involved in a weak intra­molecular C—H⋯O hydrogen bond, which generates an S(6) graph-set motif. In the crystal, the hybrid mol­ecules are associated in R22(14) dimeric units by weak C—H⋯O inter­actions. O—H⋯O hydrogen bonds link the water mol­ecules, forming infinite self-assembled chains along the b-axis direction to which the dimers are connected via O—H⋯N hydrogen bonding. Analysis of inter­molecular contacts using Hirshfeld surface analysis and contact enrichment ratio descriptors indicate that hydrogen bonds induced by water mol­ecules are the main driving force in the crystal packing formation.

In the title mol­ecule, C11H10N2O, the di­hydro­benzimidazol-2-one moiety is essentially planar, with the prop-2-yn-1-yl substituent rotated well out of this plane. In the crystal, C—HMthy⋯π(ring) inter­actions and C—HProp⋯ODhyr (Mthy = methyl, Prop = prop-2-yn-1-yl and Dhyr = di­hydro) hydrogen bonds form corrugated layers parallel to (10overline{1}), which are associated through additional C—HBnz⋯ODhyr (Bnz = benzene) hydrogen bonds and head-to-tail, slipped, π-stacking [centroid-to-centroid distance = 3.7712 (7) Å] inter­actions between di­hydro­benzimidazol-2-one moieties. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (44.1%), H⋯C/C⋯H (33.5%) and O⋯H/H⋯O (13.4%) inter­actions. Hydrogen-bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry calculations indicate that in the crystal, C—H⋯O hydrogen-bond energies are 46.8 and 32.5 (for C—HProp⋯ODhyr) and 20.2 (for C—HBnz⋯ODhyr) kJ mol−1. Density functional theory (DFT) optimized structures at the B3LYP/6–311 G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

The reaction of N-phenyl-1-(pyridin-2-yl)methanimine with copper chloride dihydrate produced the title neutral complex, [CuCl2(C12H10N2)(H2O)]·H2O. The CuII ion is five-coordinated in a distorted square-pyramidal geometry, in which the two N atoms of the bidentate Schiff base, as well as one chloro and a water mol­ecule, form the irregular base of the pyramidal structure. Meanwhile, the apical chloride ligand inter­acts through a strong hydrogen bond with a water mol­ecule of crystallization. In the crystal, mol­ecules are arranged in pairs, forming a stacking of symmetrical cyclic dimers that inter­act in turn through strong hydrogen bonds between the chloride ligands and both the coordinated and the crystallization water mol­ecules. The mol­ecular and electronic structures of the complex were also studied in detail using EPR (continuous and pulsed), FT–IR and Raman spectroscopy, as well as magnetization measurements. Likewise, Hirshfeld surface analysis was used to investigate the inter­molecular inter­actions in the crystal packing.

The title compound, C7H3F5INS, a penta­fluoro­sulfanyl (SF5) containing arene, was synthesized from 4-(penta­fluoro­sulfan­yl)benzo­nitrile and lithium tetra­methyl­piperidide following a variation to the standard approach, which features simple and mild conditions that allow direct access to tri-substituted SF5 inter­mediates that have not been demonstrated using previous methods. The mol­ecule displays a planar geometry with the benzene ring in the same plane as its three substituents. It lies on a mirror plane perpendicular to [010] with the iodo, cyano, and the sulfur and axial fluorine atoms of the penta­fluoro­sulfanyl substituent in the plane of the mol­ecule. The equatorial F atoms have symmetry-related counterparts generated by the mirror plane. The penta­fluoro­sulfanyl group exhibits a staggered fashion relative to the ring and the two hydrogen atoms ortho to the substituent. S—F bond lengths of the penta­fluoro­sulfanyl group are unequal: the equatorial bond facing the iodo moiety has a longer distance [1.572 (3) Å] and wider angle compared to that facing the side of the mol­ecules with two hydrogen atoms [1.561 (4) Å]. As expected, the axial S—F bond is the longest [1.582 (5) Å]. In the crystal, in-plane C—H⋯F and N⋯I inter­actions as well as out-of-plane F⋯C inter­actions are observed. According to the Hirshfeld analysis, the principal inter­molecular contacts for the title compound are F⋯H (29.4%), F⋯I (15.8%), F⋯N (11.4%), F⋯F (6.0%), N⋯I (5.6%) and F⋯C (4.5%).

The title compound, C24H27Cl2NOS, contains 1,4-benzo­thia­zine and 2,4-di­chloro­phenyl­methyl­idene units in which the di­hydro­thia­zine ring adopts a screw-boat conformation. In the crystal, inter­molecular C—HBnz⋯OThz (Bnz = benzene and Thz = thia­zine) hydrogen bonds form chains of mol­ecules extending along the a-axis direction, which are connected to their inversion-related counterparts by C—HBnz⋯ClDchlphy (Dchlphy = 2,4-di­chloro­phen­yl) hydrogen bonds and C—HDchlphy⋯π (ring) inter­actions. These double chains are further linked by C—HDchlphy⋯OThz hydrogen bonds, forming stepped layers approximately parallel to (012). The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (44.7%), C⋯H/H⋯C (23.7%), Cl⋯H/H⋯Cl (18.9%), O⋯H/H⋯O (5.0%) and S⋯H/H⋯S (4.8%) inter­actions. Hydrogen-bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, C—HDchlphy⋯OThz, C—HBnz⋯OThz and C—HBnz⋯ClDchlphy hydrogen-bond energies are 134.3, 71.2 and 34.4 kJ mol−1, respectively. Density functional theory (DFT) optimized structures at the B3LYP/6–311 G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap. The two carbon atoms at the end of the nonyl chain are disordered in a 0.562 (4)/0.438 (4) ratio.

In the title mol­ecule, C12H13N3O2S, the benzo­thia­zine moiety is slightly non-planar, with the imidazolidine portion twisted only a few degrees out of the mean plane of the former. In the crystal, a layer structure parallel to the bc plane is formed by a combination of O—HHydethy⋯NThz hydrogen bonds and weak C—HImdz⋯OImdz and C—HBnz⋯OImdz (Hydethy = hy­droxy­ethyl, Thz = thia­zole, Imdz = imidazolidine and Bnz = benzene) inter­actions, together with C—HImdz⋯π(ring) and head-to-tail slipped π-stacking [centroid-to-centroid distances = 3.6507 (7) and 3.6866 (7) Å] inter­actions between thia­zole rings. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (47.0%), H⋯O/O⋯H (16.9%), H⋯C/C⋯H (8.0%) and H⋯S/S⋯H (7.6%) inter­actions. Hydrogen bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, C—H⋯N and C—H⋯O hydrogen-bond energies are 68.5 (for O—HHydethy⋯NThz), 60.1 (for C—HBnz⋯OImdz) and 41.8 kJ mol−1 (for C—HImdz⋯OImdz). Density functional theory (DFT) optimized structures at the B3LYP/6–311 G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state.

In the title compound, [Cu(C16H8Br3N2O)2]·C2H6OS, the CuII atom is tetra­coordinated in a square-planar coordination, being surrounded by two N atoms and two O atoms from two N,O-bidentate (E)-1-[(2,4,6-tri­bromo­phen­yl)diazen­yl]naphthalen-2-olate ligands. The two N atoms and two O atoms around the metal center are trans to each other, with an O—Cu—O bond angle of 177.90 (16)° and a N—Cu—N bond angle of 177.8 (2)°. The average distances between the CuII atom and the coordinated O and N atoms are 1.892 (4) and 1.976 (4) Å, respectively. In the crystal, complexes are linked by C—H⋯O hydrogen bonds and by π–π inter­actions involving adjacent naphthalene ring systems [centroid–centroid distance = 3.679 (4) Å]. The disordered DMSO mol­ecules inter­act weakly with the complex mol­ecules, being positioned in the voids left by the packing arrangement of the square-planar complexes. The DMSO solvent mol­ecule is disordered over two positions with occupancies of 0.70 and 0.30.

The title compound, C15H14N2O2, consists of pyrrole and benzodiazepine units linked to a propargyl moiety, where the pyrrole and diazepine rings adopt half-chair and boat conformations, respectively. The absolute configuration was assigned on the the basis of l-proline, which was used in the synthesis of benzodiazepine. In the crystal, weak C—HBnz⋯ODiazp and C—HProprg⋯ODiazp (Bnz = benzene, Diazp = diazepine and Proprg = proparg­yl) hydrogen bonds link the mol­ecules into two-dimensional networks parallel to the bc plane, enclosing R44(28) ring motifs, with the networks forming oblique stacks along the a-axis direction. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (49.8%), H⋯C/C⋯H (25.7%) and H⋯O/O⋯H (20.1%) inter­actions. Hydrogen bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, C—H⋯O hydrogen-bond energies are 38.8 (for C—HBnz⋯ODiazp) and 27.1 (for C—HProprg⋯ODiazp) kJ mol−1. Density functional theory (DFT) optimized structures at the B3LYP/6–311 G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

The crystal structures of praseodymium silicide (5/4), Pr5Si4, and neodymium silicide (5/4), Nd5Si4, were redetermined using high-quality single-crystal X-ray diffraction data. The previous structure reports of Pr5Si4 were only based on powder X-ray diffraction data [Smith et al. (1967). Acta Cryst. 22 940–943; Yang et al. (2002b). J. Alloys Compd. 339, 189–194; Yang et al., (2003). J. Alloys Compd. 263, 146–153]. On the other hand, the structure of Nd5Si4 has been determined from powder data [neutron; Cadogan et al., (2002). J. Phys. Condens. Matter, 14, 7191–7200] and X-ray [Smith et al. (1967). Acta Cryst. 22 940–943; Yang et al. (2002b). J. Alloys Compd. 339, 189–194; Yang et al., (2003). J. Alloys Compd. 263, 146–153] and single-crystal data with isotropic atomic displacement parameters [Roger et al., (2006). J. Alloys Compd. 415, 73–84]. In addition, the anisotropic atomic displacement parameters for all atomic sites have been determined for the first time. These compounds are confirmed to have the tetra­gonal Zr5Si4-type structure (space group: P41212), as reported previously (Smith et al., 1967). The structure is built up by distorted body-centered cubes consisting of Pr(Nd) atoms, which are linked to each other by edge-sharing to form a three-dimensional framework. This framework delimits zigzag channels in which the silicon dimers are situated.

The title compound, C11H9N3OS, (I), crystallizes in the monoclinic space group P21/n. The mol­ecular conformation is nearly planar and features an intra­molecular chalcogen bond between the thio­phene S and the imine N atoms. Within the crystal, the strongest inter­actions between mol­ecules are the N—H⋯O hydrogen bonds, which organize them into inversion dimers. The dimers are linked through short C—H⋯N contacts and are stacked into layers propagating in the (001) plane. The crystal structure features π–π stacking between the pyridine aromatic ring and the azomethine double bond. The calculated energies of pairwise inter­molecular inter­actions within the stacks are considerably larger than those found for the inter­actions between the layers.

The title compound, C24H18FNO3, crystallizes in the monoclinic centrosymmetric space group P21/n and its mol­ecular conformation is stabilized via C—H⋯O intra­molecular inter­actions. The supra­molecular network mainly comprises C—H⋯O, C—H⋯F and C—H⋯π inter­actions, which contribute towards the formation of the crystal structure. The different inter­molecular inter­actions have been further analysed via Hirshfeld surface analysis and fingerprint plots.

The title compound, C19H16ClNO3S, consists of chloro­phenyl methyl­idene and di­hydro­benzo­thia­zine units linked to an acetate moiety, where the thia­zine ring adopts a screw-boat conformation. In the crystal, two sets of weak C—HPh⋯ODbt (Ph = phenyl and Dbt = di­hydro­benzo­thia­zine) hydrogen bonds form layers of mol­ecules parallel to the bc plane. The layers stack along the a-axis direction with inter­calation of the ester chains. The crystal studied was a two component twin with a refined BASF of 0.34961 (5). The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (37.5%), H⋯C/C⋯H (24.6%) and H⋯O/O⋯H (16.7%) inter­actions. Hydrogen-bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, C—HPh⋯ODbt hydrogen bond energies are 38.3 and 30.3 kJ mol−1. Density functional theory (DFT) optimized structures at the B3LYP/ 6–311 G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap. Moreover, the anti­bacterial activity of the title compound has been evaluated against gram-positive and gram-negative bacteria.

The title compound, C18H16N2O2, consists of perimidine and meth­oxy­phenol units, where the tricyclic perimidine unit contains a naphthalene ring system and a non-planar C4N2 ring adopting an envelope conformation with the NCN group hinged by 47.44 (7)° with respect to the best plane of the other five atoms. In the crystal, O—HPhnl⋯NPrmdn and N—HPrmdn⋯OPhnl (Phnl = phenol and Prmdn = perimidine) hydrogen bonds link the mol­ecules into infinite chains along the b-axis direction. Weak C—H⋯π inter­actions may further stabilize the crystal structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (49.0%), H⋯C/C⋯H (35.8%) and H⋯O/O⋯H (12.0%) inter­actions. Hydrogen bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, the O—HPhnl⋯NPrmdn and N—HPrmdn⋯OPhnl hydrogen-bond energies are 58.4 and 38.0 kJ mol−1, respectively. Density functional theory (DFT) optimized structures at the B3LYP/ 6–311 G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

The crystal structure of MgCO3-II has long been discussed in the literature where DFT-based model calculations predict a pressure-induced transition of the carbon atom from the sp2 to the sp3 type of bonding. We have now determined the crystal structure of iron-bearing MgCO3-II based on single-crystal X-ray diffraction measurements using synchrotron radiation. We laser-heated a synthetic (Mg0.85Fe0.15)CO3 single crystal at 2500 K and 98 GPa and observed the formation of a monoclinic phase with composition (Mg2.53Fe0.47)C3O9 in the space group C2/m that contains tetra­hedrally coordinated carbon, where CO44− tetra­hedra are linked by corner-sharing oxygen atoms to form three-membered C3O96− ring anions. The crystal structure of (Mg0.85Fe0.15)CO3 (magnesium iron carbonate) at 98 GPa and 300 K is reported here as well. In comparison with previous structure-prediction calculations and powder X-ray diffraction data, our structural data provide reliable information from experiments regarding atomic positions, bond lengths, and bond angles.

Exact and approximate mathematical formulas of equatorial aberration for powder diffraction data collected with an Si strip X-ray detector in continuous-scan integration mode are presented. An approximate formula is applied to treat the experimental data measured with a commercial powder diffractometer.

Hybrid photon-counting detectors are widely established at third-generation synchrotron facilities and the specifications of the Pilatus3 X CdTe were quickly recognized as highly promising in charge-density investigations. This is mainly attributable to the detection efficiency in the high-energy X-ray regime, in combination with a dynamic range and noise level that should overcome the perpetual problem of detecting strong and weak data simultaneously. These benefits, however, come at the expense of a persistent problem for high diffracted beam flux, which is particularly problematic in single-crystal diffraction of materials with strong scattering power and sharp diffraction peaks. Here, an in-depth examination of data collected on an inorganic material, FeSb2, and an organic semiconductor, rubrene, revealed systematic differences in strong intensities for different incoming beam fluxes, and the implemented detector intensity corrections were found to be inadequate. Only significant beam attenuation for the collection of strong reflections was able to circumvent this systematic error. All data were collected on a bending-magnet beamline at a third-generation synchrotron radiation facility, so undulator and wiggler beamlines and fourth-generation synchrotrons will be even more prone to this error. On the other hand, the low background now allows for an accurate measurement of very weak intensities, and it is shown that it is possible to extract structure factors of exceptional quality using standard crystallographic software for data processing (SAINT-Plus, SADABS and SORTAV), although special attention has to be paid to the estimation of the background. This study resulted in electron-density models of substantially higher accuracy and precision compared with a previous investigation, thus for the first time fulfilling the promise of photon-counting detectors for very accurate structure factor measurements.

The development of ultrashort X-ray pulse sources requires optics that keep the pulse length as short as possible. One source of pulse stretching is the penetration of the pulse into a crystal during diffraction. Another source is the inclination of the intensity front when the diffraction is asymmetric. The theory of short X-ray pulse diffraction has been well developed by many authors. As it is rather complicated, it is sometimes difficult to foresee the pulse behavior (mainly stretching) during diffraction in various crystal arrangements. In this article, a simple model is suggested that gives a qualitatively similar shape to the diffracted pulse which follows from exact theory. It allows proposal of what experimental arrangement is optimal to minimize the pulse stretching during diffraction. First, the effect of pulse stretching due to penetration into a crystal surface is studied. On the basis of this, the pulse profile change during diffraction by two crystals, either symmetric or asymmetric, is predicted.

High-quality single-crystal X-ray diffraction measurements are a prerequisite for obtaining precise and reliable structure data and electron densities. The single crystal should therefore fulfill several conditions, of which a regular defined shape is of particularly high importance for compounds consisting of heavy elements with high X-ray absorption coefficients. The absorption of X-rays passing through a 50 µm-thick LiNbO3 crystal can reduce the transmission of Mo Kα radiation by several tens of percent, which makes an absorption correction of the reflection intensities necessary. In order to reduce ambiguities concerning the shape of a crystal, used for the necessary absorption correction, a method for preparation of regularly shaped single crystals out of large samples is presented and evaluated. This method utilizes a focused ion beam to cut crystals with defined size and shape reproducibly and carefully without splintering. For evaluation, a single-crystal X-ray diffraction study using a laboratory diffractometer is presented, comparing differently prepared LiNbO3 crystals originating from the same macroscopic crystal plate. Results of the data reduction, structure refinement and electron density reconstruction indicate qualitatively similar values for all prepared crystals. Thus, the different preparation techniques have a smaller impact than expected. However, the atomic coordinates, electron densities and atomic charges are supposed to be more reliable since the focused-ion-beam-prepared crystal exhibits the smallest extinction influences. This preparation technique is especially recommended for susceptible samples, for cases where a minimal invasive preparation procedure is needed, and for the preparation of crystals from specific areas, complex material architectures and materials that cannot be prepared with common methods (breaking or grinding).

Ni-based intermetallics are promising materials for forming efficient contacts in GeSn-based Si photonic devices. However, the role that Sn might have during the Ni/GeSn solid-state reaction (SSR) is not fully understood. A comprehensive analysis focused on Sn segregation during the Ni/GeSn SSR was carried out. In situ X-ray diffraction and cross-section transmission electron microscopy measurements coupled with energy-dispersive X-ray spectrometry and electron energy-loss spectroscopy atomic mappings were performed to follow the phase sequence, Sn distribution and segregation. The results showed that, during the SSR, Sn was incorporated into the intermetallic phases. Sn segregation happened first around the grain boundaries (GBs) and then towards the surface. Sn accumulation around GBs hampered atom diffusion, delaying the growth of the Ni(GeSn) phase. Higher thermal budgets will thus be mandatory for formation of contacts in high-Sn-content photonic devices, which could be detrimental for thermal stability.

Traditionally small-molecule crystallographers have not usually observed or recognized significant radiation damage to their samples during diffraction experiments. However, the increased flux densities provided by third-generation synchrotrons have resulted in increasing numbers of observations of this phenomenon. The diversity of types of small-molecule systems means it is not yet possible to propose a general mechanism for their radiation-induced sample decay, however characterization of the effects will permit attempts to understand and mitigate it. Here, systematic experiments are reported on the effects that sample temperature and beam attenuation have on radiation damage progression, allowing qualitative and quantitative assessment of their impact on crystals of a small-molecule test sample. To allow inter-comparison of different measurements, radiation-damage metrics (diffraction-intensity decline, resolution fall-off, scaling B-factor increase) are plotted against the absorbed dose. For ease-of-dose calculations, the software developed for protein crystallography, RADDOSE-3D, has been modified for use in small-molecule crystallography. It is intended that these initial experiments will assist in establishing protocols for small-molecule crystallographers to optimize the diffraction signal from their samples prior to the onset of the deleterious effects of radiation damage.

Advances in both non-resonant and resonant X-ray magnetic diffraction since the 1980s have provided researchers with a powerful tool for exploring the spin, orbital and ion degrees of freedom in magnetic solids, as well as parsing their interplay. Here, we discuss key issues for performing X-ray magnetic diffraction on single-crystal samples under high pressure (above 40 GPa) and at cryogenic temperatures (4 K). We present case studies of both non-resonant and resonant X-ray magnetic diffraction under pressure for a spin-flip transition in an incommensurate spin-density-wave material and a continuous quantum phase transition of a commensurate all-in–all-out antiferromagnet. Both cases use diamond-anvil-cell technologies at third-generation synchrotron radiation sources. In addition to the exploration of the athermal emergence and evolution of antiferromagnetism discussed here, these techniques can be applied to the study of the pressure evolution of weak charge order such as charge-density waves, antiferro-type orbital order, the charge anisotropic tensor susceptibility and charge superlattices associated with either primary spin order or softened phonons.