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A novel monoclinic phase of human insulin co-crystallized with m-cresol was structurally characterized by means of powder and single-crystal X-ray diffraction.

The concept of statistical signal detection by controlling the false-discovery rate (FDR) to aid the atomic model interpretation of cryo-EM density maps is reviewed. The recommended usage of the FDR software tool is presented together with its successful integration into the CCP-EM suite.

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.

Rice AKR in the apo structure reveals the ordered open conformation and its key residues which form the substrate channel wall and determine its substrate preference for straight-chain aldehydes.

The asymmetric unit of the title MOF, [Zn5(C14H5NO10S2)2(OH)2(H2O)10]n comprises three ZnII atoms, one of which is located on a centre of inversion, a tetra-negative carboxyl­ate ligand, one μ3-hydroxide and five water mol­ecules, each of which is coordinated. The ZnII atom, lying on a centre of inversion, is coordinated by trans sulfoxide-O atoms and four water mol­ecules in an octa­hedral geometry. Another ZnII atom is coordinated by two carboxyl­ate-O atoms, one hy­droxy-O, one sulfoxide-O and a water-O atom to define a distorted trigonal–bipyramidal geometry; a close Zn⋯O(carboxyl­ate) inter­action derived from an asymmetrically coordinating ligand (Zn—O = 1.95 and 3.07 Å) suggests a 5 + 1 coordination geometry. The third ZnII atom is coordinated in an octa­hedral fashion by two hy­droxy-O atoms, one carboxyl­ate-O, one sulfoxide-O and two water-O atoms, the latter being mutually cis. In all, the carboxyl­ate ligand binds six ZnII ions leading to a three-dimensional architecture. In the crystal, all acidic donors form hydrogen bonds to oxygen acceptors to contribute to the stability of the three-dimensional architecture.

The redetermination of the crystal structure of barium oxidotellurate(IV) monohydrate allowed the localization of the hydrogen atoms that were not determined in the previous study [Nielsen, Hazell & Rasmussen (1971). Acta Chem. Scand. 25, 3037–3042], thus making an unambiguous assignment of the hydrogen-bonding scheme possible. The crystal structure shows a layered arrangement parallel to (001), consisting of edge-sharing [BaO6(H2O)] polyhedra and flanked by isolated [TeO3] trigonal pyramids on the top and bottom. O—H⋯O hydrogen bonds of medium strength link adjacent layers along [001].

In the title compound, [Ba(C10H20O5)2][Zn(NCS)4], the 15-crown-5 mol­ecules are disordered over two positions with site occupancies of 0.706 (4) and 0.294 (4). The Ba2+ ions are sandwiched between the 15-crown-5 rings and Zn2+ ions are surrounded by four N atoms from the thio­cyanate ligands in a distorted tetra­hedral geometry. The crystal studied was refined as an inversion twin.

Single crystals of the title complex, [Zn(C7H5N2O4)2(C2H6OS)2] or [Zn(NBZH)2(DMSO)2], were isolated from a dimethyl sulfoxide (DMSO) solution containing [Zn(NBZH)2]·2H2O (NBZH = 3-nitro­benzo­hydroxamate anion). The asymmetric unit comprises of one O,O'-chelating NBZH anion, one O-bound DMSO ligand and one zinc(II) cation localized on an inversion centre. The three-dimensional crystal packing includes N—H⋯O and C—H⋯O hydrogen bonding, as well as O⋯H and H⋯H contacts identified by Hirshfeld isosurface analysis.

In the title compound, [Zn(C9H6O4)]n, the ZnII cations are coordinated in a tetra­hedral fashion by carboxyl­ate O-atom donors belonging to four 4-(carb­oxy­meth­yl) benzoate (4-cmb) ligands. Each 4-cmb ligand binds to four ZnII cations in an exo­tetra­dentate fashion to create a non-inter­penetrated [Zn(4-cmb)]n three-dimensional coordination polymer network with a new non-diamondoid 66 topology. The crystal studied was refined as an inversion twin.

The complete mol­ecule of the title compound, C32H22F12N4O2, is generated by a crystallographic twofold axis aligned parallel to [010]. The F atoms of one of the CF3 groups are disordered over three orientations in a 0.6: 0.2: 0.2 ratio. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, forming zigzag chains propagating along the a-axis direction. In addition, weak C—H⋯O and C—H⋯F bonds are observed. The contribution of the disordered solvent to the scattering was removed using the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9–18] of PLATON. The solvent contribution is not included in the reported mol­ecular weight and density.

The title compound, d-(+)-glucosa­mmonium potassium tetra­thio­cyanato­cobaltate(II) dihydrate, K(C6H14NO5)[Co(NCS)4]·2H2O or (GlcNH)(K)[Co(NCS)4]·2H2O, has been obtained as a side product of an incomplete salt metathesis reaction of d-(+)-glucosa­mine hydro­chloride (GlcN·HCl) and K2[Co(NCS)4]. The asymmetric unit contains a d-(+)-glucos­ammonium cation, a potassium cation, a tetra­iso­thio­cyanato­cobalt(II) complex anion and two water mol­ecules. The water mol­ecules coordinate to the potassium cation, which is further coordinated via three short K+⋯SCN− contacts involving three [Co(NCS)4]2− complex anions and via three O atoms of two d-(+)-glucosa­mmonium cations, leading to an overall eightfold coordination around the potassium cation. Hydrogen-bonding inter­actions between the building blocks consolidate the three-dimensional arrangement.

The title two-dimensional coordination polymer, [Zn(C6H5PO3)]n, was synthesized serendipitously by reacting a tetra­phospho­nate cavitand Tiiii[C3H7, CH3, C6H5] and Zn(CH3COO)2·2H2O in a DMF/H2O mixture. The basic conditions of the reaction cleaved the phospho­nate bridges at the upper rim of the cavitand, making them available for reaction with the zinc ions. The coordination polymer can be described as an inorganic layer in which zinc coordinates the oxygen atoms of the phospho­nate groups in a distorted tetra­hedral environment, while the phenyl groups, which are statistically disordered over two orientations, point up and down with respect to the layer. The layers inter­act through van der Waals inter­actions. The crystal studied was refined as a two-component twin.

The title hepta­nuclear alkoxido(oxido)vanadium(V) oxide cluster complex, [V7(C10H19O)O17(C18H24N2)3]·CH3CN, was obtained by the reaction of [V8O20(C18H24N2)4] with 4-tert-butyl­cyclo­hexa­nol (mixture of cis and trans) in a mixed CHCl3/CH3CN solvent. The complex has a V7O18N6 core with approximately Cs symmetry, which is composed of two VO4 tetra­hedra, two VO6 octa­hedra and three VO4N2 octa­hedra. In the crystal, these complexes are linked together by weak inter­molecular C—H⋯O hydrogen bonds between the 4,4'-di-tert-butyl-2,2'-bi­pyridine ligand and the V7O18N6 core, forming a one-dimensional network along the c-axis direction. Besides the complex, the asymmetric unit contains one CH3CN solvent mol­ecule. The contribution of other disordered solvent mol­ecules to the scattering was removed using the SQUEEZE option in PLATON [Spek (2015). Acta Cryst. C71, 9–18]. The unknown solvent mol­ecules are not considered in the chemical formula and other crystal data.

The crystal structure of title salt, C22H46N42+·2NO3−·2H2O, has been determined using synchrotron radiation at 220 K. The structure determination reveals that protonation has occurred at diagonally opposite amine N atoms. The asymmetric unit contains half a centrosymmetric dication, one nitrate anion and one water mol­ecule. The mol­ecular dication, C22H46N42+, together with the nitrate anion and hydrate water mol­ecule are involved in an extensive range of hydrogen bonds. The mol­ecule is stabilized, as is the conformation of the dication, by forming inter­molecular N—H⋯O, O—H⋯O, together with intra­molecular N—H⋯N hydrogen bonds.

Rb0.21(H2O)yWS2, rubidium hydrate di­thio­tungstate, is a new quasi two-dimensional sulfide. Its crystal structure consists of ordered WS2 layers, separated by disordered Rb+ ions and water mol­ecules. All atomic sites are located on mirror planes. The WS2 layers are composed of edge-sharing [WS6] octa­hedra and extend parallel to (001). The presence of structural water was revealed by thermogravimetry, but the position and exact amount could not be determined in the present study. The temperature dependence of the electrical resistance indicates that Rb0.21(H2O)yWS2 is semiconducting between 80–300 K.

From solutions of prehnitene and the ternary halides (SnCl)[MCl4] (M = Al, Ga) in chloro­benzene, the new cationic SnII–π-arene complexes catena-poly[[chlorido­aluminate(III)]-tri-μ-chlorido-4':1κ2Cl,1:2κ4Cl-[(η6-1,2,3,4-tetra­meth­yl­benzene)­tin(II)]-di-μ-chlorido-2:3κ4Cl-[(η6-1,2,3,4-tetra­methyl­benzene)­tin(II)]-di-μ-chlorido-3:4κ4Cl-[chlorido­aluminate(III)]-μ-chlorido-4:1'κ2Cl], [Al2Sn2Cl10(C10H14)2]n, (1) and catena-poly[[chlorido­gallate(III)]-tri-μ-chlor­ido-4':1κ2Cl,1:2κ4Cl-[(η6-1,2,3,4-tetra­methyl­benzene)­tin(II)]-di-μ-chlorido-2:3κ4Cl-[(η6-1,2,3,4-tetra­methyl­benzene)­tin(II)]-di-μ-chlorido-3:4κ4Cl-[chlor­ido­gallate(III)]-μ-chlorido-4:1'κ2Cl], [Ga2Sn2Cl10(C10H14)2]n, (2), were isolated. In these first main-group metal–prehnitene complexes, the distorted η6 arene π-bonding to the tin atoms of the Sn2Cl22+ moieties in the centre of [{1,2,3,4-(CH3)4C6H2}2Sn2Cl2][MCl4]2 repeating units (site symmetry overline{1}) is characterized by: (i) a significant ring slippage of ca 0.4 Å indicated by the dispersion of Sn—C distances [1: 2.881 (2)–3.216 (2) Å; 2: 2.891 (3)–3.214 (3) Å]; (ii) the non-methyl-substituted arene C atoms positioned closest to the SnII central atom; (iii) a pronounced tilt of the plane of the arene ligand against the plane of the central (Sn2Cl2)2+ four-membered ring species [1: 15.59 (11)°, 2: 15.69 (9)°]; (iv) metal–arene bonding of medium strength as illustrated by application of the bond-valence method in an indirect manner, defining the π-arene bonding inter­action of the SnII central atoms as s(SnII—arene) = 2 − Σs(SnII—Cl), that gives s(SnII—arene) = 0.37 and 0.38 valence units for the aluminate and the gallate, respectively, indicating that comparatively strong main-group metal–arene bonding is present and in line with the expectation that [AlCl4]− is the slightly weaker coordinating anion as compared to [GaCl4]−.

In the crystal structure of the isostructural title compounds, namely {2,6-bis­[(di-tert-butyl­phosphan­yl)­oxy]-4-hy­droxy­phen­yl}chlorido­palladium(II), [Pd(C22H39O3P2)Cl], 1, and {2,6-bis­[(di-tert-butyl­phosphan­yl)­oxy]-4-hy­droxy­phen­yl}chlorido­platinum(II), [Pt(C22H39O3P2)Cl], 2, the metal centres are coordinated in a distorted square-planar fashion by the POCOP pincer fragment and the chloride ligand. Both complexes form strong hydrogen-bonded chain structures through an inter­action of the OH group in the 4-position of the aromatic POCOP backbone with the halide ligand.

The asymmetric unit of the title compound, [Zn(C6H8N4B)2(C12H8N2)], comprises one half of a ZnII cation (site symmetry 2), one di­hydro­bis­(pyrazol-1-yl)borate ligand in a general position, and one half of a phenanthroline ligand, the other half being completed by twofold rotation symmetry. The ZnII cation is coordinated in form of a slightly distorted octa­hedron by the N atoms of a phenanthroline ligand and by two pairs of N atoms of symmetry-related di­hydro­bis­(pyrazol-1-yl)borate ligands. The discrete complexes are arranged into columns that elongate in the c-axis direction with a parallel alignment of the phenanthroline ligands, indicating weak π–π inter­actions.

Three new isotypic heteropolynuclear complexes, namely penta­aqua­carbonato­penta­kis­(glycinehydroxamato)nitrato­penta­copper(II)lanthanide(III) x-hydrate, [LnCu5(GlyHA)5(CO3)(NO3)(H2O)5]·xH2O (GlyHA2− is glycine­hydrox­amate, N-hy­droxy­glycinamidate or amino­aceto­hydroxamate, C2H4N2O22−), with lanthanide(III) (LnIII) = gadolinium (Gd, 1, x = 3.5), dysprosium (Dy, 2, x = 3.28) and holmium (Ho, 3, x = 3.445), within a 15-metallacrown-5 class were obtained on reaction of lanthanide(III) nitrate, copper(II) acetate and sodium glycinehydroxamate. Complexes 1–3 contain five copper(II) ions and five bridging GlyHA2− anions, forming a [CuGlyHA]5 metallamacrocyclic core. The LnIII ions are coordinated to the metallamacrocycle through five O-donor hydroxamates. The electroneutrality of complexes 1–3 is achieved by a bidentate carbonate anion coordinated to the LnIII ion and a monodentate nitrate anion coordinated apically to one of the copper(II) ions of the metallamacrocycle. The lattice parameters of complexes 1–3 are similar to those previously reported for an EuIII–CuII 15-metallacrown-5 complex with glycine­hydroxamate of proposed composition [EuCu5(GlyHA)5(OH)(NO3)2(H2O)4]·3.5H2O [Stemmler et al. (1999). Inorg. Chem. 38, 2807–2817]. High-quality X-ray data obtained for 1–3 have allowed a re-evaluation of the X-ray data solution proposed earlier for the EuCu5 complex and suggest that the formula is actually [EuCu5(GlyHA)5(CO3)(NO3)(H2O)5]·3.5H2O.

Reaction of 2-(anthracen-9-yl)phenol (HOPhAn, 1) with divalent Yb[N(SiMe3)2]2·2THF in THF–toluene mixtures affords the mixed-valence YbII–YbIII dimer {[2-(anthracen-9-yl)phenolato-κO]bis­(tetra­hydro­furan)­ytterbium(III)}-tris­[μ-2-(anthracen-9-yl)phenolato]-κ4O:O;κO:1,2-η,κO-{[2-(anthracen-9-yl)phenolato-κO]ytterbium(II)} toluene tris­olvate, [Yb2(C20H13O)5(C4H8O)2]·3C7H7 or [YbIII(THF)2(OPhAn)](μ-OPhAn)3[YbII(OPhAn)]·3C7H7 (2), as the major product. It crystallized as a toluene tris­olvate. The Yb—O bond lengths in the crystal structure of this dimer clearly identify the YbII and YbIII centres. Inter­estingly, the formally four-coordinate YbII centre shows a close contact with one anthracene C—C bond of a bridging OPhAn ligand, bringing the formal coordination number to five.

The reaction of bis­(3-oxo-1,3-di­phenyl­prop-1-enolato-κ2O,O')zinc(II), [Zn(dbm)2], with tris­[4-(pyridin-3-yl)phen­yl]amine (T3PyA) in tetra­hydro­furan (THF) afforded the title crystalline coordination polymer, {[Zn(C15H11O2)2(C33H24N4)]·C4H8O}n. The asymmetric unit contains two independent halves of Zn(dbm)2, one T3PyA and one THF. Each ZnII atom is located on an inversion centre and adopts an elongated octa­hedral coordination geometry, ligated by four O atoms of two dbm ligands in equatorial positions and by two N atoms of pyridine moieties from two different bridging T3PyA ligands in axial positions. The crystal packing shows a one-dimensional polymer chain in which the two pyridyl groups of the T3PyA ligand bridge two independent Zn atoms of Zn(dbm)2. In the crystal, the coordination polymer chains are linked via C—H⋯π inter­actions into a sheet structure parallel to (010). The sheets are cross-linked via further C—H⋯π inter­actions into a three-dimensional network. The solvate THF mol­ecule shows disorder over two sets of atomic sites having occupancies of 0.631 (7) and 0.369 (7).

In the title compound, bis­(2-meth­oxy­ethyl xanthato-κS)(N,N,N',N'-tetra­methyl­ethylenedi­amine-κ2N,N')zinc(II) acetone hemisolvate, [Zn(C4H7O2S2)2(C6H16N2)]·0.5C3H6O, the ZnII ion is coordinated by two N atoms of the N,N,N',N'-tetra­methyl­ethylenedi­amine ligand and two S atoms from two 2-meth­oxy­ethyl xanthate ligands. The amine ligand is disordered over two orientations and was modelled with refined occupancies of 0.538 (6) and 0.462 (6). The mol­ecular structure features two C—H⋯O and two C—H⋯S intra­molecular inter­actions. In the crystal, mol­ecules are linked by weak C—H⋯O and C—H⋯S hydrogen bonds, forming a three-dimensional supra­molecular architecture. The mol­ecular structure was optimized using density functional theory (DFT) at the B3LYP/6–311 G(d,p) level. The smallest HOMO–LUMO energy gap (3.19 eV) indicates the suitability of this crystal for optoelectronic applications. The mol­ecular electrostatic potential (MEP) further identifies the positive, negative and neutral electrostatic potential regions of the mol­ecules. Half a mol­ecule of disordered acetone was removed with the solvent-mask procedure in OLEX2 [Dolomanov et al. (2009). J. Appl. Cryst. 42, 339–341] and this contribition is included in the formula.

In the title com­pound, C29H22N4O3, the carbazole system forms a dihedral angle of 68.45 (3)° with the mean plane of the bi­pyridine ring system. The bi­pyridine ring system, with two meth­oxy substituents, is approximately planar (r.m.s. deviation = 0.0670 Å), with a dihedral angle of 7.91 (13)° between the planes of the two pyridine rings. Intra­molecular C—H⋯O/N hydrogen bonds may promote the planarity of the bipyridyl ring system. In the pyridyl-substituted carbazole fragment, the pyridine ring is tilted by 56.65 (4)° with respect to the mean plane of the carbazole system (r.m.s. deviation = 0.0191 Å). In the crystal, adjacent mol­ecules are connected via C—H⋯O/N hydrogen bonds and C—H⋯π inter­actions, resulting in the formation of a three-dimensional (3D) supra­molecular network. In addition, the 3D structure contains inter­molecular π–π stacking inter­actions, with centroid–centroid distances of 3.5634 (12) Å between pyridine rings. The title com­pound exhibits a high energy gap (3.48 eV) and triplet energy (2.64 eV), indicating that it could be a suitable host material in organic light-emitting diode (OLED) applications.

The new title one-dimensional CdII coordination polymer, [Cd(C10H10N2)2(μ1,3-N3)2]n, has been synthesized and structurally characterized by single-crystal X-ray diffraction. The asymmetric unit consists of a CdII ion, one azide and one 1-benzyl­imidazole (bzi) ligand. The CdII ion is located on an inversion centre and is surrounded in a distorted octa­hedral coordination sphere by six N atoms from four symmetry-related azide ligands and two symmetry-related bzi ligands. The CdII ions are linked by double azide bridging ligands within a μ1,3-N3 end-to-end (EE) coordination mode, leading to a one-dimensional linear structure extending parallel to [100]. The supra­molecular framework is stabilized by the presence of weak C—H⋯N inter­actions, π–π stacking [centroid-to-centroid distance of 3.832 (2) Å] and C—H⋯π inter­actions between neighbouring chains.

The title compound, [IrZnI2(C10H15)(C3H9P)2]·0.5C6H6 or [Cp*(PMe3)2Ir]-[ZnI2] (Cp* = cyclo-C5Me5) was obtained and characterized as its benzene solvate [Cp*(PMe3)2Ir]-[ZnI2]·0.5C6H6. The bimetallic complex in this structure contains the Lewis-acidic fragment ZnI2 bonded to the Lewis-basic fragment Cp*(PMe3)2Ir, with an Ir—Zn bond distance of 2.452 (1) Å. The compound was obtained by reacting [Cp*(PMe3)IrI2] with 2-Ad2Zn (2-Ad = 2-adamant­yl), resulting in the reduction of the IrIII complex and formation of the IrI–ZnII adduct. The crystal studied was a twin by non-merohedry with a refined BASF parameter of 0.223 (1).

In the title compound, (2,2'-bi­pyridine-κ2N,N')bis­(2-meth­oxy­ethyl xanthato-κS)zinc(II), [Zn(C4H7O2S2)2(C10H8N2)], the ZnII ion is coordinated to two N atoms of the 2,2'-bi­pyridine ligand and two S atoms from two 2-meth­oxy­ethyl xanthate ligands. The ZnII ion lies on a crystallographic twofold rotation axis and has distorted tetra­hedral coordination geometry. In the crystal, mol­ecules are linked by weak C—H⋯O hydrogen bonds, forming supramolecular chains propagating along the a-axis direction. Weak intra­molecular C—H⋯S hydrogen bonds are also observed. The inter­molecular contacts in the crystal were further analysed using Hirshfield surface analysis, which indicates that the most significant contacts are H⋯H (36.3%), followed by S⋯H/H⋯S (24.7%), C⋯H/H⋯C (15.1%), O⋯H/H⋯O (14.4%), N⋯H/H⋯N (4.1%) and C⋯C (2.9%).

The unit cell of the title compound, [Zn(C17H18N3O4)2]·CH4O·C2H6O, contains two complex mol­ecules related by an inversion centre, plus one methanol and one ethanol solvent molecule per complex molecule. In each complex, two deprotonated pyridine aroylhydrazone ligands {3,4,5-trimeth­oxy-N'-[1-(pyridin-2-yl)ethyl­idene]benzohydrazide} coordinate to the ZnII ion through the N atoms of the pyridine group and the ketamine, and, additionally, through the O atom of the enolate group. In the crystal, dimers are formed by π–π inter­actions between the planar ligand moieties, which are further connected by C⋯O and C⋯C inter­actions. The inter­molecular inter­actions were investigated using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing that the most important contributions for the crystal packing are from H⋯H (44.8%), H⋯C/C⋯H (22.2%), H⋯O/O⋯H (18.7%) and C⋯C (3.9%) inter­actions.

In the title compound, [Zn(C50H36N6O5)], the ZnII cation is chelated by four pyrrole N atoms of the porphyrinate anion and coordinated by a symmetry-generated keto O atom of the diazo­ester group in a distorted square-pyramidal geometry. The mean Zn—N(pyrrole) bond length is 2.058 Å and the Zn—O(diazo­ester) bond length is 2.179 (4) Å. The zinc cation is displaced by 0.2202 (13) Å from the N4C20 mean plane of the porphyrinate anion toward the O atom; the involvement of this atom leads to a [100] polymeric chain in the crystal.

The crystal structure of title salt, C14H36N44+·2ClO4−·2Cl−, has been determined using synchrotron radiation at 220 K. The structure determination reveals that protonation has occurred at all four amine N atoms. The asymmetric unit contains one half-cation (completed by crystallographic inversion symmetry), one perchlorate anion and one chloride anion. A distortion of the perchlorate anion is due to its involvement in hydrogen-bonding inter­actions with the cations. The crystal structure is consolidated by inter­molecular hydrogen bonds involving the 1,4,8,11-tetra­methyl-1,4,8,11-tetra­azonia­cyclo­tetra­decane N—H and C—H groups as donor groups, and the O atoms of the perchlorate and chloride anion as acceptor groups, giving rise to a three-dimensional network.

A new organic–inorganic hybrid salt [L]2[MnCl4] (I) where L+ is the 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium cation, is built of discrete organic cations and tetra­chlorido­manganate(II) anions. The L+ cation was formed in situ in the oxidative cyclo­condensation of 2-pyridine­carbaldehyde and CH3NH2·HCl in methanol. The structure was refined as a two-component twin using PLATON (Spek, 2020) to de-twin the data. The twin law (−1 0 0 0 − 1 0 0.5 0 1) was applied in the refinement where the twin component fraction refined to 0.155 (1). The compound crystallizes in the space group P21/c with two crystallographically non-equivalent cations in the asymmetric unit, which possess similar structural conformations. The fused pyridinium and imidazolium rings of the cations are virtually coplanar [dihedral angles are 0.89 (18) and 0.78 (17)°]; the pendant pyridyl rings are twisted by 36.83 (14) and 36.14 (13)° with respect to the planes of the remaining atoms of the cations. The tetra­hedral MnCl42– anion is slightly distorted with the Mn—Cl distances falling in the range 2.3469 (10)–2.3941 (9) Å. The distortion value of 0.044 relative to the ideal tetra­hedron was obtained by continuous shape measurement (CShM) analysis. In the crystal, the cations and anions form separate stacks propagating along the a-axis direction. The organic cations display weak π–π stacking. The anions, which are stacked identically one above the other, demonstrate loose packing; the minimum Mn⋯Mn separation in the cation stack is approximately 7.49 Å. The investigation of the fluorescent properties of a powdered sample of (I) showed no emission. X-band EPR data for (I) at 293 and 77 K revealed broad fine structure signals, indicating moderate zero-field splitting.

The whole mol­ecule of the cadmium(II) complex, di­iodido­{N,N',N'',N'''-[pyrazine-2,3,5,6-tetra­yltetra­kis­(methyl­ene)]tetra­kis­(N-methyl­aniline)-κ3N2,N1,N6}cadmium(II), [CdI2(C36H40N6)], (I), of the ligand N,N',N'',N'''-[pyrazine-2,3,5,6-tetra­yltetra­kis­(methyl­ene)]tetra­kis­(N-methyl­aniline) (L), is generated by a twofold rotation symmetry; the twofold axis bis­ects the cadmium atom and the nitro­gen atoms of the pyrazine ring. The ligand coordinates in a mono-tridentate manner and the cadmium atom has a fivefold CdN3I2 coordination environment with a distorted shape. In the zinc(II) complex, dichlorido{N,N',N'',N'''-[pyrazine-2,3,5,6-tetra­yltetra­kis­(methyl­ene)]tetra­kis­(N-methyl­aniline)-κ3N2,N1,N6}zinc(II) di­chloro­methane 0.6-solvate, [ZnCl2(C36H40N6)]·0.6CH2Cl2, (II), ligand L also coordinates in a mono-tridentate manner and the zinc atom has a fivefold ZnN3Cl2 coordination environment with a distorted shape. It crystallized as a partial di­chloro­methane solvate. In the crystal of I, the complex mol­ecules are linked by weak C—H⋯I contacts, forming ribbons propagating along [100]. In the crystal of II, the complex mol­ecules are linked by a series of C—H⋯π inter­actions, forming layers lying parallel to the (1overline{1}1) plane. In the crystals of both compounds there are metal–halide⋯π(pyrazine) contacts present. The Hirshfeld analyses confirm the importance of the C—H⋯halide contacts in the crystal packing of both compounds.

In the title mol­ecular salt, 1,3-dimethyl-2,6-dioxo-2,3,6,7-tetra­hydro-1H-purin-9-ium aqua­tri­chlorido­zincate(II), (C7H9N4O2)[ZnCl3(H2O)], the fused ring system of the cation is close to planar, with the largest deviation from the mean plane being 0.037 (3) Å. In the complex anion, the ZnII cation is coordinated by three chloride ions and one oxygen atom from the water ligand in a distorted tetra­hedral geometry. In the crystal, inversion dimers between pairs of cations linked by pairwise N—H⋯O hydrogen bonds generate R22(10) rings. The anions are linked into dimers by pairs of O—H⋯Cl hydrogen bonds and the respective dimers are linked by O—H⋯O and N—H⋯Cl hydrogen bonds. Together, these generate a three-dimensional supra­molecular network. Hirshfeld surfaces were generated to gain further insight into the packing.

The crystal structure of title compound, (C14H36N4)[CrO3Cl]2Cl2, has been determined by synchrotron radiation X-ray crystallography at 220 K. The macrocyclic cation lies across a crystallographic inversion center and hence the asymmetric unit contains one half of the organic cation, one chloro­chromate anion and one chloride anion. Both the Cl− anion and chloro­chromate Cl atom are involved in hydrogen bonding. In the crystal, hydrogen bonds involving the 1,4,8,11-tetra­methyl-1,4,8,11-tetra­azonia­cyclo­tetra­decane (TMC) N—H groups and C—H groups as donor groups and three O atoms of the chloro­chromate and the chloride anion as acceptor groups link the components, giving rise to a three-dimensional network.

Five examples each of 3-(5-ar­yloxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-1-[4-(prop-2-yn-1-yl­oxy)phen­yl]prop-2-en-1-ones and the corresponding 1-(4-azido­phen­yl)-3-(5-ar­yloxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)prop-2-en-1-ones have been synthesized in a highly efficient manner, starting from a common source precursor, and structures have been determined for three examples of each type. In each of 3-[5-(2-chloro­phen­oxy)-3-methyl-1-phenyl-1H-pyrazol-4-yl]-1-[4-(prop-2-yn-1-yl­oxy)phen­yl]prop-2-en-1-one, C28H21ClN2O3, (Ib), the isomeric 3-[5-(2-chloro­phen­oxy)-3-methyl-1-phenyl-1H-pyrazol-4-yl]-1-[4-(prop-2-yn-1-yl­oxy)phen­yl]prop-2-en-1-one, (Ic), and 3-[3-methyl-5-(naphthalen-2-yl­oxy)-1-phenyl-1H-pyrazol-4-yl]-1-[4-(prop-2-yn­yloxy)phen­yl]prop-2-en-1-one, C32H24N2O3, (Ie), the mol­ecules are linked into chains of rings, formed by two independent C—H⋯O hydrogen bonds in (Ib) and by a combination of C—H⋯O and C—H⋯π(arene) hydrogen bonds in each of (Ic) and (Ie). There are no direction-specific inter­molecular inter­actions in the structure of 1-(4-azido­phen­yl)-3-[3-methyl-5-(2-methyl­phen­oxy)-1-phenyl-1H-pyrazol-4-yl]prop-2-en-1-one, C26H21N5O2, (IIa). In 1-(4-azido­phen­yl)-3-[5-(2,4-di­chloro­phen­oxy)-3-methyl-1-phenyl-1H-pyrazol-4-yl]prop-2-en-1-one, C25H17Cl2N5O2, (IId), the di­chloro­phenyl group is disordered over two sets of atomic sites having occupancies 0.55 (4) and 0.45 (4), and the mol­ecules are linked by a single C—H⋯O hydrogen bond to form cyclic, centrosymmetric R22(20) dimers. Similar dimers are formed in 1-(4-azido­phen­yl)-3-[3-methyl-5-(naphthalen-2-yl­oxy)-1-phenyl-1H-pyrazol-4-yl]prop-2-en-1-one, C29H21N5O2, (IIe), but here the dimers are linked into a chain of rings by two independent C—H..π(arene) hydrogen bonds. Comparisons are made between the mol­ecular conformations within both series of compounds.

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.

In this work, two methods of high-resolution X-ray data refinement: multipole refinement (MM) and Hirshfeld atom refinement (HAR) – together with X-ray wavefunction refinement (XWR) – are applied to investigate the refinement of positions and anisotropic thermal motion of hydrogen atoms, experiment-based reconstruction of electron density, refinement of anharmonic thermal vibrations, as well as the effects of excluding the weakest reflections in the refinement. The study is based on X-ray data sets of varying quality collected for the crystals of four quinoline derivatives with Cl, Br, I atoms and the -S-Ph group as substituents. Energetic investigations are performed, comprising the calculation of the energy of intermolecular interactions, cohesive and geometrical relaxation energy. The results obtained for experimentally derived structures are verified against the values calculated for structures optimized using dispersion-corrected periodic density functional theory. For the high-quality data sets (the Cl and -S-Ph compounds), both MM and XWR could be successfully used to refine the atomic displacement parameters and the positions of hydrogen atoms; however, the bond lengths obtained with XWR were more precise and closer to the theoretical values. In the application to the more challenging data sets (the Br and I compounds), only XWR enabled free refinement of hydrogen atom geometrical parameters, nevertheless, the results clearly showed poor data quality. For both refinement methods, the energy values (intermolecular interactions, cohesive and relaxation) calculated for the experimental structures were in similar agreement with the values associated with the optimized structures – the most significant divergences were observed when experimental geometries were biased by poor data quality. XWR was found to be more robust in avoiding incorrect distortions of the reconstructed electron density as a result of data quality issues. Based on the problem of anharmonic thermal motion refinement, this study reveals that for the most correct interpretation of the obtained results, it is necessary to use the complete data set, including the weak reflections in order to draw conclusions.

Ependymin was first discovered as a predominant protein in brain extracellular fluid in fish and was suggested to be involved in functions mostly related to learning and memory. Orthologous proteins to ependymin called ependymin-related proteins (EPDRs) have been found to exist in various tissues from sea urchins to humans, yet their functional role remains to be revealed. In this study, the structures of EPDR1 from frog, mouse and human were determined and analyzed. All of the EPDR1s fold into a dimer using a monomeric subunit that is mostly made up of two stacking antiparallel β-sheets with a curvature on one side, resulting in the formation of a deep hydrophobic pocket. All six of the cysteine residues in the monomeric subunit participate in the formation of three intramolecular disulfide bonds. Other interesting features of EPDR1 include two asparagine residues with glycosylation and a Ca2+-binding site. The EPDR1 fold is very similar to the folds of bacterial VioE and LolA/LolB, which also use a similar hydrophobic pocket for their respective functions as a hydrophobic substrate-binding enzyme and a lipoprotein carrier, respectively. A further fatty-acid binding assay using EPDR1 suggests that it indeed binds to fatty acids, presumably via this pocket. Additional interactome analysis of EPDR1 showed that EPDR1 interacts with insulin-like growth factor 2 receptor and flotillin proteins, which are known to be involved in protein and vesicle translocation.

The local Fourier-space relation between diffracted intensity I, diffraction wavevector q and dose D, ilde I(q,D), is key to probing and understanding radiation damage by X-rays and energetic particles in both diffraction and imaging experiments. The models used in protein crystallography for the last 50 years provide good fits to experimental I(q) versus nominal dose data, but have unclear physical significance. More recently, a fit to diffraction and imaging experiments suggested that the maximum tolerable dose varies as q−1 or linearly with resolution. Here, it is shown that crystallographic data have been strongly perturbed by the effects of spatially nonuniform crystal irradiation and diffraction during data collection. Reanalysis shows that these data are consistent with a purely exponential local dose dependence, ilde I(q,D) = I0(q)exp[−D/De(q)], where De(q) ∝ qα with α ≃ 1.7. A physics-based model for radiation damage, in which damage events occurring at random locations within a sample each cause energy deposition and blurring of the electron density within a small volume, predicts this exponential variation with dose for all q values and a decay exponent α ≃ 2 in two and three dimensions, roughly consistent with both diffraction and imaging experiments over more than two orders of magnitude in resolution. The B-factor model used to account for radiation damage in crystallographic scaling programs is consistent with α = 2, but may not accurately capture the dose dependencies of structure factors under typical nonuniform illumination conditions. The strong q dependence of radiation-induced diffraction decays implies that the previously proposed 20–30 MGy dose limit for protein crystallography should be replaced by a resolution-dependent dose limit that, for atomic resolution data sets, will be much smaller. The results suggest that the physics underlying basic experimental trends in radiation damage at T ≃ 100 K is straightforward and universal. Deviations of the local I(q, D) from strictly exponential behavior may provide mechanistic insights, especially into the radiation-damage processes responsible for the greatly increased radiation sensitivity observed at T ≃ 300 K.

The disposition of functional groups can induce variations in the nature and type of interactions and hence affect the molecular recognition and self-assembly mechanism in cocrystals. To better understand the formation of cocrystals on a molecular level, the effects of disposition of functional groups on the formation of cocrystals were systematically and comprehensively investigated using cresol isomers (o-, m-, p-cresol) as model compounds. Consistency and variability in these cocrystals containing positional isomers were found and analyzed. The structures, molecular recognition and self-assembly mechanism of supramolecular synthons in solution and in their corresponding cocrystals were verified by a combined experimental and theoretical calculation approach. It was found that the heterosynthons (heterotrimer or heterodimer) combined with O—H⋯N hydrogen bonding played a significant role. Hirshfeld surface analysis and computed interaction energy values were used to determine the hierarchical ordering of the weak interactions. The quantitative analyses of charge transfers and molecular electrostatic potential were also applied to reveal and verify the reasons for consistency and variability. Finally, the molecular recognition, self-assembly and evolution process of the supramolecular synthons in solution were investigated. The results confirm that the supramolecular synthon structures formed initially in solution would be carried over to the final cocrystals, and the supramolecular synthon structures are the precursors of cocrystals and the information memory of the cocrystallization process, which is evidence for classical nucleation theory.

In the past three years, Dirac half-metals (DHMs) have attracted considerable attention and become a high-profile topic in spintronics becuase of their excellent physical properties such as 100% spin polarization and massless Dirac fermions. Two-dimensional DHMs proposed recently have not yet been experimentally synthesized and thus remain theoretical. As a result, their characteristics cannot be experimentally confirmed. In addition, many theoretically predicted Dirac materials have only a single cone, resulting in a nonlinear electromagnetic response with insufficient intensity and inadequate transport carrier efficiency near the Fermi level. Therefore, after several attempts, we have focused on a novel class of DHMs with multiple Dirac crossings to address the above limitations. In particular, we direct our attention to three-dimensional bulk materials. In this study, the discovery via first principles of an experimentally synthesized DHM LaNiO3 with many Dirac cones and complete spin polarization near the Fermi level is reported. It is also shown that the crystal structures of these materials are strongly correlated with their physical properties. The results indicate that many rhombohedral materials with the general formula LnNiO3 (Ln = La, Ce, Nd, Pm, Gd, Tb, Dy, Ho, Er, Lu) in the space group R3c are potential DHMs with multiple Dirac cones.

Tannerella forsythia is an oral dysbiotic periodontopathogen involved in severe human periodontal disease. As part of its virulence factor armamentarium, at the site of colonization it secretes mirolysin, a metallopeptidase of the unicellular pappalysin family, as a zymogen that is proteolytically auto-activated extracellularly at the Ser54–Arg55 bond. Crystal structures of the catalytically impaired promirolysin point mutant E225A at 1.4 and 1.6 Å revealed that latency is exerted by an N-terminal 34-residue pro-segment that shields the front surface of the 274-residue catalytic domain, thus preventing substrate access. The catalytic domain conforms to the metzincin clan of metallopeptidases and contains a double calcium site, which acts as a calcium switch for activity. The pro-segment traverses the active-site cleft in the opposite direction to the substrate, which precludes its cleavage. It is anchored to the mature enzyme through residue Arg21, which intrudes into the specificity pocket in cleft sub-site S1'. Moreover, residue Cys23 within a conserved cysteine–glycine motif blocks the catalytic zinc ion by a cysteine-switch mechanism, first described for mammalian matrix metallopeptidases. In addition, a 1.5 Å structure was obtained for a complex of mature mirolysin and a tetradecapeptide, which filled the cleft from sub-site S1' to S6'. A citrate molecule in S1 completed a product-complex mimic that unveiled the mechanism of substrate binding and cleavage by mirolysin, the catalytic domain of which was already preformed in the zymogen. These results, including a preference for cleavage before basic residues, are likely to be valid for other unicellular pappalysins derived from archaea, bacteria, cyanobacteria, algae and fungi, including archetypal ulilysin from Methanosarcina acetivorans. They may further apply, at least in part, to the multi-domain orthologues of higher organisms.

Co-crystallization is a phenomenon widely employed to enhance the physio-chemical and biological properties of active pharmaceutical ingredients (APIs). Exemestane, or 6-methyl­ideneandrosta-1,4-diene-3,17-dione, is an anabolic steroid used as an irreversible steroidal aromatase inhibitor, which is in clinical use to treat breast cancer. The present study deals with the synthesis of co-crystals of exemestane with thio­urea by liquid-assisted grinding. The purity and homogeneity of the exemestane–thio­urea (1:1) co-crystal were confirmed by single-crystal X-ray diffraction followed by thermal stability analysis on the basis of differential scanning calorimetry and thermogravimetric analysis. Detailed geometric analysis of the co-crystal demonstrated that a 1:1 co-crystal stoichiometry is sustained by N—H⋯O hydrogen bonding between the amine (NH2) groups of thio­urea and the carbonyl group of exemestane. The synthesized co-crystal exhibited potent urease inhibition activity in vitro (IC50 = 3.86 ± 0.31 µg ml−1) compared with the API (exemestane), which was found to be inactive, and the co-former (thio­urea) (IC50 = 21.0 ± 1.25 µg ml−1), which is also an established tested standard for urease inhibition assays in vitro. The promising results of the present study highlight the significance of co-crystallization as a crystal engineering tool to improve the efficacy of pharmaceutical ingredients. Furthermore, the role of various hydrogen bonds in the crystal stability is successfully analysed quantitatively using Hirshfeld surface analysis.

SMC complexes play a central role in chromosome organization in all domains of life. The bacterial Smc–ScpAB complex is a three-subunit complex composed of Smc, ScpA and ScpB. ScpA bridges the two ATPase domains of the Smc homodimer, while ScpB, which belongs to the kite family of proteins, interacts with ScpA. The three subunits are known to be equally important for the function of Smc–ScpAB in bacteria. From crystallographic and biochemical studies, evidence is provided that six archaeal ScpA proteins are unable to interact with the only putative ScpB found in these species. Structure-based sequence alignment reveals that these archaeal ScpAs lack the ScpB-binding segment that is commonly present in the middle of bacterial ScpA sequences, which is thus responsible for their inability to interact with ScpB. ScpA proteins lacking the ScpB-binding segment are found to prevail in archaea. Moreover, two archaeal ScpA proteins with a longer middle region also failed to bind their putative ScpB partner. Furthermore, all or most species belonging to five out of 14 euryarchaeotal orders contain Smc and ScpA but not a detectable ScpB homologue. These data support the notion that archaeal Smc-based complexes generally function as a two-subunit complex composed of only Smc and ScpA.

Single crystals of the m = 8 member of the low-dimensional monophosphate tungsten bronzes (PO2)4(WO3)2m family were grown by chemical vapour transport technique and the high crystalline quality obtained allowed a reinvestigation of the physical and structural properties. Resistivity measurements revealed three anomalies at TC1 = 258 K, TC2 = 245 K and TC3 = 140 K, never observed until now. Parallel X-ray diffraction investigations showed a specific signature associated with three structural transitions, i.e. the appearance of different sets of satellite reflections below TC1, TC2 and TC3. Several harmonics of intense satellite reflections were observed, reflecting the non-sinusoidal nature of the structural modulations and a strong electron–phonon coupling in the material. These transitions could be associated with the formation of three successive unconventional charge density wave states.