ShelXle: a Qt graphical user interface for SHELXL

Synthetic strategies for new vanadium oxyfluorides containing novel building blocks: structures of V(iv) and V(v) containing Sr4V3O5F13, Pb7V4O8F18, Pb2VO2F5, and Pb2VOF6

Four novel vanadium oxyfluorides (VOFs) featuring new crystallographic building blocks were crystallizedviaa mild hydrothermal route.

Binuclear complexes of Ni(i) from 4-terphenyldithiophenol

The preparation and characterisation of binuclear Ni(i) complexes from a 4-terphenyldithiophenol ligand is described.

Synthesis of substituted β-diketiminate gallium hydrides via oxidative addition of H–O bonds

Substituted β-diketiminate gallium hydrides of the general formulaLGa(H)X have been obtained from the oxidative addition reactions of compounds with OH groups intoLGa (L= HC[CMeNAr]₂⁻, Ar = 2,6-iPr₂C₆H₃).

New oxovanadium(iv) complexes with pincer ligand obtained in situ: experimental and theoretical studies on the structure, spectroscopic properties and antitumour activity

Experimental and theoretical studies on the structure and spectroscopic properties of two complexes: [VOL¹(NCS)₂] (1) and [VOL¹(NCS)₂]·C₆H₅CH₃ (2) where L¹-N,N-bis(3,5-dimethylpyrazol-1-ylmethyl)amine have been reported.

New Ni(ii) 1,2-bis(diphenylphosphino)ethane dithiolates: crystallographic, computational and Hirshfeld surface analyses

Three new Ni(ii) dppe dithiolates have been synthesized and the nature of weak interactions have been addressed using computational and Hirshfeld surface analyses.

Structural diversity of late transition metal complexes with flexible tetra-NHC ligands

Silver complexes with flexible tetra-NHC ligands were used as transmetalation agent to access a series of d-block metal complexes.

Synthesis, structure and reactivity of a donor-stabilised silylene with a bulky bidentate benzamidinato ligand

A novel donor-stabilised silicon(ii) complex with an SiN₃ skeleton was synthesised and its reactivity profile was characterised (reactions with N₂O, S₈, Se, Te, Me₃SiN₃, PhSCH₂N₃ and [Fe(CO)₅]).

MeL2Zn2(μ-1,6-Ph2-N6) – a building block for new hexazene complexes

^MeL₂Zn₂(μ-1,6-Ph₂-N₆) 1 (^MeL = HC[C(Me)N(2,4,6-Me₃C₆H₂)]₂) serves as hexazene transfer reagent in reactions with main group metal and transition metal complexes containing M–Me units.

Thermodynamic parameters of the pedal motion in the crystal structures of two bromomethylated azobenzenes

Differences in the thermodynamic parameters of the central N-atoms' pedal motion in two bromomethylated azobenzenes were determined by multi-temperature X-ray diffraction, and rationalized by packing studies.

Homo- and heteroalumoxane silicates

Homo- or hetero alumoxanesilicates or bridged M–OH–M hydroxidesilicates with unusual or unprecedented inorganic cores have been obtained in reactions between 1 and nBuLi, AlMe₃, GaMe₃ or ZnMe₂. The aluminum derivatives serve as models for MAO.

Elucidating the elusive crystal structure of 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine

2,4,6-Tris(2-pyrimidyl)-1,3,5-triazine has been synthesized using two approaches: via trimerization of 2-cyanopyrimidine at 160 °C and by the reaction of 2-cyanopyrimidine with pyrimidine-2-carboximidamide.

Dichlorodioxomolybdenum(vi) complexes bearing oxygen-donor ligands as olefin epoxidation catalysts

The complexes [MoO₂Cl₂(N,N-dimethylbenzamide)₂] and [MoO₂Cl₂(N,N′-diethyloxamide)] are active olefin epoxidation catalysts and can be easily recycled when using ionic liquid solvents.

Study of temperature and ligand flexibility effects on coordination polymer formation from cyclobutanetetracarboxylic acid

Three novel coordination polymers (CPs) from rctt-H4Cbtc and 4,4’-bpe with Zn and Ni metal nodes have been synthesized. The CP derivates of Zn are an unusual example for the preparation of metastable phases involving temperature dependent and concomitant transformation.

Crystal structure refinement with SHELXL

The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as `a CIF') containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.

Determination of potential main sites of apixaban binding in human serum albumin by combined spectroscopic and docking investigations

Probing apixaban binding to human serum albumin: combining spectroscopic methods and docking investigations.

Insights into the fatty acid ester norethisterone enanthate binding to human albumin: fluorescence, circular dichroism, and docking investigations

Fatty acid ester norethisterone enanthate binding to human albumin.

The crystal structures of four N-(4-halophen-yl)-4-oxo-4H-chromene-3-carboxamides

In four N-(4-halophen­yl)-4-oxo-4H-chromene-3-carboxamides, halo = -F, -Cl, -Br and -I, the mol­ecules are essentially planar and exhibit anti conformations with respect to the C—N rotamer of the amide and with cis geometries with respect to the relative positions of the C3_arom—C2_arom bond of the chromone ring and the carbonyl group of the amide.

Four N-(4-halophen­yl)-4-oxo-4H-chromene-3-carboxamides (halo = F, Cl, Br and I), N-(4-fluoro­phen­yl)-4-oxo-4H-chromene-3-carboxamide, C₁₆H₁₀FNO₃, N-(4-chloro­phen­yl)-4-oxo-4H-chromene-3-carboxamide, C₁₆H₁₀ClNO₃, N-(4-bromo­phen­yl)-4-oxo-4H-chromene-3-carboxamide, C₁₆H₁₀BrNO₃, N-(4-iodo­phen­yl)-4-oxo-4H-chromene-3-carboxamide, C₁₆H₁₀INO₃, have been structurally characterized. The mol­ecules are essentially planar and each exhibits an anti conformation with respect to the C—N rotamer of the amide and a cis geometry with respect to the relative positions of the C_arom—C_arom bond of the chromone ring and the carbonyl group of the amide. The structures each exhibit an intra­molecular hydrogen-bonding network comprising an N—H⋯O hydrogen bond between the amide N atom and the O atom of the carbonyl group of the pyrone ring, forming an S(6) ring, and a weak C_arom—H⋯O inter­action with the O atom of the carbonyl group of the amide as acceptor, which forms another S(6) ring. All four compounds have the same supra­molecular structure, consisting of R₂²(13) rings that are propagated along the a-axis direction by unit translation. There is π–π stacking involving inversion-related mol­ecules in each structure.

Rare-earth metal methylidene complexes with Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3 core structure

Although protected from intermolecular deactivation by a picket-fence-type arrangement of bulky amido ligands the CH₂²⁻ moiety is readily converted into oxo species.

Reactivity of halfsandwich rare-earth metal methylaluminates toward potassium (2,4,6-tri-tert-butylphenyl)amide and 1-adamantylamine

Donor functionalities drastically affect salt-metathetical methylaluminato–amido exchange reactions in Cp^RLn(AlMe₄)₂ by triggering methylaluminate cleavage and C–H bond activation of proximal aliphatic groups.

pH-metric chemical speciation modeling and studies of in vitro antidiabetic effects of bis[(imidazolyl)carboxylato]oxidovanadium(IV) complexes

A range of bidentate N,O-donor ligands of the imidazolyl-carboxylate moiety, which partially mimic naturally occurring bioligands, were prepared and reacted with the oxidovanadium(IV) ion to form the corresponding bis-coordinated oxidovanadium(IV) complexes. The aqueous pH-metric chemical speciation was investigated using glass electrode potentiometry, which allowed for the determination of protonation and stability constants of the ligands and complexes, respectively. The species distribution diagrams generated from this information gave evidence that the bis[(imidazolyl)carboxylato]oxovanadium(IV) complexes possess a broad pH-metric stability. The complexes improved glucose uptake in cell cultures using 3T3-L1 adipocytes, C2C12 muscle cells and Chang liver cells. The PTP inhibition studies indicated that the mechanism underlying insulin-stimulated glucose uptake was possibly via the protein tyrosine phosphorylation through the inhibition of the protein tyrosine phosphatase 1B (PTP 1B). The vanadium compounds also demonstrated the inhibition of D-dimer formation, suggesting that these compounds could potentially relieve a hypercoagulative state in diabetic patients.

Crystal structure of methyl 2-(2H-1,3-benzodioxol-5-yl)-7,9-di-bromo-8-oxo-1-oxa-spiro-[4.5]deca-2,6,9-triene-3-car-boxyl-ate

The title compound, C18H12Br2O6, was synthesized from Morita-Baylis-Hillman adducts. It incorporates the bromin-ated spiro-hexa-dienone moiety typically exhibited by compounds of this class that exhibit biological activity. Both the brominated cyclo-hexa-dienone and the central five-membered rings are nearly planar (r.m.s. deviations of 0.044 and 0.016 Å, respectively), being almost perpendicularly oriented [inter-planar angle = 89.47 (5)°]. With respect to the central five-membered ring, the brominated cyclo-hexa-dienone ring, the benzodioxol ring and the carboxyl-ate fragment make C-O-C-C, O-C-C-C and C-C-C-O dihedral angles of -122.11 (8), -27.20 (11) and -8.40 (12)°, respectively. An intra-molecular C-H⋯O hydrogen bond occurs. In the crystal, mol-ecules are linked by non-classical C-H⋯O and C-H⋯Br hydrogen bonds resulting in a molecular packing in which the brominated rings are in a head-to-head orientation, forming well marked planes parallel to the b axis.

Crystal structure of di-μ-chloro-acetato-hexa-kis-(di-methyl-formamide)-tetra-kis-(μ-N,2-dioxido-benzene-1-carboximidato)tetra-manganese(III)disodium dimethyl-formamide disolvate

The title compound consists of a macrocyclic ring with an Mn^III—N—O repeat unit that occurs four times, producing a mol­ecule with an overall square structure. Two Na⁺ ions are captured above and below the central cavity of the mol­ecule.

The synthesis, crystal structure, and FT–IR data for the title compound, [Na₂Mn₄(C₂H₂ClO₂)₂(C₇H₄NO₃)₄(C₃H₇NO)₆]·2C₃H₇NO or Na₂(O₂CCH₂Cl)₂[12-MC_Mn^IIIN(shi)-4](DMF)₆·2DMF, where MC is metallacrown, shi³⁻ is salicyl­hydroximate, and DMF is N,N-di­methyl­formamide, is reported. The macrocyclic metallacrown consists of an –[Mn^III—N—O]₄– ring repeat unit and the metallacrown captures two Na⁺ ions in the central cavity above and below the plane of the metallacrown. Each Na⁺ ion is seven-coordinate and is bridged to two ring Mn^III ions, through either a coordinating DMF mol­ecule or a chloro­acetate anion. The ring Mn^III ions have either a tetra­gonally distorted octa­hedral geometry or a distorted square-pyramidal geometry. Weak C—H⋯O inter­actions, in addition to pure van der Waals forces, contribute to the overall packing of the mol­ecules. The complete molecule has inversion symmetry and is disordered over two sets of sites with an occupancy ratio of 0.8783 (7):0.1217 (7). The solvent molecule is also disordered over two sets of sites, with an occupancy ratio of 0.615 (5):0.385 (5).

Aspherical-atom modeling of coordination compounds by single-crystal X-ray diffraction allows the correct metal atom to be identified

Single-crystal X-ray diffraction (XRD) is often considered the gold standard in analytical chemistry, as it allows element identification as well as determination of atom connectivity and the solid-state structure of completely unknown samples. Element assignment is based on the number of electrons of an atom, so that a distinction of neighboring heavier elements in the periodic table by XRD is often difficult. A computationally efficient procedure for aspherical-atom least-squares refinement of conventional diffraction data of organometallic compounds is proposed. The iterative procedure is conceptually similar to Hirshfeld-atom refinement (Acta Crystallogr. Sect. A- 2008, 64, 383-393; IUCrJ. 2014, 1,61-79), but it relies on tabulated invariom scattering factors (Acta Crystallogr. Sect. B- 2013, 69, 91-104) and the Hansen/Coppens multipole model; disordered structures can be handled as well. Five linear-coordinate 3d metal complexes, for which the wrong element is found if standard independent-atom model scattering factors are relied upon, are studied, and it is shown that only aspherical-atom scattering factors allow a reliable assignment. The influence of anomalous dispersion in identifying the correct element is investigated and discussed.

Univalent Gallium Complexes of Simple and ansa-Arene Ligands: Effects on the Polymerization of Isobutylene

Using [Ga(C6 H5 F)2 ]+ [Al(ORF )4 ]- (1) (RF =C(CF3 )3 ) as starting material, we isolated bis- and tris-η6 -coordinated gallium(I) arene complex salts of p-xylene (1,4-Me2 C6 H4 ), hexamethylbenzene (C6 Me6 ), diphenylethane (PhC2 H4 Ph), and m-terphenyl (1,3-Ph2 C6 H4 ): [Ga(1,4-Me2 C6 H4 )2.5 ]+ (2+ ), [Ga(C6 Me6 )2 ]+ (3+ ), [Ga(PhC2 H4 Ph)]+ (4+ ) and [(C6 H5 F)Ga(μ-1,3-Ph2 C6 H4 )2 Ga(C6 H5 F)]2+ (52+ ). 4+ is the first structurally characterized ansa-like bent sandwich chelate of univalent gallium and 52+ the first binuclear gallium(I) complex without a GaGa bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI-BP86/SV(P) level), [Ga(PhC2 H4 Ph)]+ [Al(ORF )4 ]- (4) and [(C6 H5 F)Ga(μ-1,3-Ph2 C6 H4 )2 Ga(C6 H5 F)]2+ {[Al(ORF )4 ] - }2 (5), featuring ansa-arene ligands, were tested as catalysts for the synthesis of highly reactive polyisobutylene (HR-PIB). In comparison to the recently published 1 and the [Ga(1,3,5-Me3 C6 H3 )2 ]+ [Al(ORF )4 ]- salt (6) (1,3,5-Me3 C6 H3 =mesitylene), 4 and 5 gave slightly reduced reactivities. This allowed for favorably increased polymerization temperatures of up to +15 °C, while yielding HR-PIB with high contents of terminal olefinic double bonds (α-contents=84-93 %), low molecular weights (Mn =1000-3000 g mol-1 ) and good monomer conversions (up to 83 % in two hours). While the chelate complexes delivered more favorable results than 1 and 6, the reaction kinetics resembled and thus concurred with the recently proposed coordinative polymerization mechanism.

Photoluminescent and magnetic properties of lanthanide containing apatites: NaxLn10-x(SiO4)6O2-yFy, CaxLn10-x(SiO4)6O2-yFy (Ln = Eu, Gd, and Sm), Gd9.34(SiO4)6O2, and K1.32Pr8.68(SiO4)6O1.36F0.64

Single crystals of NaEu(9)(SiO(4))(6)O(2), Na(1.5)Eu(8.5)(SiO(4))(6)OF, Na(1.64)Gd(8.36)(SiO(4))(6)O(0.72)F(1.28), Gd(9.34)(SiO(4))(6)O(2), Ca(2.6)Eu(7.4)(SiO(4))(6)O(1.4)F(0.6), Ca(4.02)Sm(5.98)(SiO(4))(6)F(2), and K(1.32)Pr(8.68)(SiO(4))(6)O(1.36)F(0.64) and powders of NaEu(9)(SiO(4))(6)O(2), Na(1.5)Eu(8.5)(SiO(4))(6)OF, Eu(9.34)(SiO(4))(6)O(2), and Gd(9.34)(SiO(4))(6)O(2) were synthesized via flux growth in selected alkali-fluoride melts. All of the compounds adopt the apatite structure with space group P6(3)/m. Luminescence and magnetic data were collected on NaEu(9)(SiO(4))(6)O(2), Na(1.5)Eu(8.5)(SiO(4))(6)OF, Eu(9.34)(SiO(4))(6)O(2), and Gd(9.34)(SiO(4))(6)O(2). Luminescent data indicate that changing the cations and anions that surround the lanthanide site does not change the luminescent properties, making apatites versatile structures for optical materials.

Ion permeation in K⁺ channels occurs by direct Coulomb knock-on

Potassium channels selectively conduct K(+) ions across cellular membranes with extraordinary efficiency. Their selectivity filter exhibits four binding sites with approximately equal electron density in crystal structures with high K(+) concentrations, previously thought to reflect a superposition of alternating ion- and water-occupied states. Consequently, cotranslocation of ions with water has become a widely accepted ion conduction mechanism for potassium channels. By analyzing more than 1300 permeation events from molecular dynamics simulations at physiological voltages, we observed instead that permeation occurs via ion-ion contacts between neighboring K(+) ions. Coulomb repulsion between adjacent ions is found to be the key to high-efficiency K(+) conduction. Crystallographic data are consistent with directly neighboring K(+) ions in the selectivity filter, and our model offers an intuitive explanation for the high throughput rates of K(+) channels.

Contributions of charge-density research to medicinal chemistry

This article reviews efforts in accurate experimental charge-density studies with relevance to medicinal chemistry. Initially, classical charge-density studies that measure electron density distribution via least-squares refinement of aspherical-atom population parameters are summarized. Next, interaction density is discussed as an idealized situation resembling drug-receptor interactions. Scattering-factor databases play an increasing role in charge-density research, and they can be applied both to small-molecule and macromolecular structures in refinement and analysis; software development facilitates their use. Therefore combining both of these complementary branches of X-ray crystallography is recommended, and examples are given where such a combination already proved useful. On the side of the experiment, new pixel detectors are allowing rapid measurements, thereby enabling both high-throughput small-molecule studies and macromolecular structure determination to higher resolutions. Currently, the most ambitious studies compute intermolecular interaction energies of drug-receptor complexes, and it is recommended that future studies benefit from recent method developments. Selected new developments in theoretical charge-density studies are discussed with emphasis on its symbiotic relation to crystallography.

Crystal structure of μ-1κC:2(η(2))-carbonyl-carbonyl-1κC-chlorido-2κCl-μ-chlorido-borylene-1:2κ(2) B:B-[1(η(5))-penta-methyl-cyclo-penta-dien-yl](tri-cyclo-hexyl-phosphane-2κP)iron(II)platinum(II) benzene monosolvate

The title compound [η⁵-(C₅(CH₃)₅)(CO)Fe{(μ-BCl)(μ-CO)}PtCl(P(C₆H₁₁)₃)]·C₆H₆ shows a piano-stool coordination geometry at the Fe^II atom and a distorted square-planar coordination geometry at the Pt atom. Both metals are bridged by one carbonyl and one chlorido­borylene unit. Additionally, one benzene solvent mol­ecule aligns in a staggered position relative to the (penta­meth­yl)cyclo­penta­dienyl ligand of the Fe^II centre.

In the mol­ecular structure of the dinuclear title compound [η⁵-(C₅(CH₃)₅)(CO)Fe{(μ-BCl)(μ-CO)}PtCl(P(C₆H₁₁)₃)]·C₆H₆, the two metal atoms, iron(II) and platinum(II), are bridged by one carbonyl (μ-CO) and one chlorido­borylene ligand (μ-BCl). The Pt^II atom is additionally bound to a chloride ligand situated trans to the bridging borylene, and a tri­cyclo­hexyl­phosphane ligand (PCy₃) trans to the carbonyl ligand, forming a distorted square-planar structural motif at the Pt^II atom. The Fe^II atom is bound to a penta­methyl­cyclo­penta­dienyl ligand [η⁵-C₅(CH₃)₅] and one carbonyl ligand (CO), forming a piano-stool structure. Additionally, one benzene solvent mol­ecule is incorporated into the crystal structure, positioned staggered relative to the penta­methyl­cyclo­penta­dienyl ligand at the Fe^II atom, with a centroid–centroid separation of 3.630 (2) Å.

Synthesis of hexaphyrins and N-fused pentaphyrins bearing pyridin-4-ylsulfanyl groups

In recent years much attention has been devoted to expanded macrocyclic chemistry. Nevertheless, while several advancements were achieved in the synthesis of novel expanded porphyrin architectures, not much has been developed in the functionalization of these macrocycles. This report shows the selective replacement of the p-fluorine atoms of meso-pentakis(pentafluorophenyl) N-fused [22]pentaphyrin and meso-hexakis(pentafluorophenyl) [26]hexaphyrin with 4-mercaptopyridine moieties, thus increasing their potential as ligands for coordination chemistry and catalysis or electronic transfer applications striving new synthetic methodologies and a new set of specific applications for this type of compounds.

Narcissistic self-sorting vs. statistic ligand shuffling within a series of phenothiazine-based coordination cages

Previously, we introduced a series of anion-binding interpenetrated double-cages based on phenothiazine and its mono- and di-S-oxygenated derivatives. Here, we complete the structural comparison of the three related assemblies by an X-ray single crystal analysis of the sulfone derivative. We further show that the three palladium cages coexist in solution upon post-assembly mixing due to the very slow ligand exchange whereas treatment of binary mixtures of the corresponding ligands with Pd(II) leads to the formation of mixed cages comprising a statistical ligand distribution. In contrast, mixtures of one of these ligands with a shorter ligand derivative lead to narcissistic self-assembly into a double-cage and a coexisting small monomeric cage, regardless of the order of mixing and Pd(II) addition.

Hume-Rothery phase-inspired metal-rich molecules: cluster expansion of [Ni(ZnMe)₆(ZnCp*)₂] by face capping with Ni⁰(η⁶-toluene) and Ni(I)(η⁵-Cp*)

The novel all-hydrocarbon ligand-stabilized binuclear clusters of metal-core composition Ni2Zn7E, [(η(5)-Cp*)Ni2(ZnMe)6(ZnCp*)(ECp*)] (1-Zn, E = Zn; 1-Ga, E = Ga) and [(η(6)-toluene)Ni2(ZnCp*)2(ZnMe)6] (2; Cp* = pentamethylcyclopentadienyl), were obtained via Ga/Zn and Al/Zn exchange reactions using the starting compounds [Ni2(ECp*)3(η(2)-C2H4)2] (E = Al/Ga) and an excess of ZnMe2 (Me = CH3). Compounds 1-Zn and 1-Ga are very closely related and differ only by one Zn or Ga atom in the group 12/13 metal shell (Zn/Ga) around the two Ni centers. Accordingly, 1-Zn is EPR-active and 1-Ga is EPR-silent. The compounds were derived as a crystalline product mixture. All new compounds were characterized by (1)H and (13)C NMR and electron paramagnetic resonance (EPR) spectroscopy, mass spectrometric analysis using liquid-injection field desorption ionization, and elemental analysis, and their molecular structures were determined by single-crystal X-ray diffraction studies. In addition, the electronic structure has been investigated by DFT and QTAIM calculations, which suggest that there is a Ni1-Ni2 binding interaction. Similar to Zn-rich intermetallic phases of the Hume-Rothery type, the transition metals (here Ni) are distributed in a matrix of Zn atoms to yield highly Zn-coordinated environments. The organic residues, ancillary ligands (Me, Cp*, and toluene), can be viewed as the "protecting" shell of the 10-metal-atom core structures. The soft and flexible binding properties of Cp* and transferability of Me substituents between groups 12 and 13 are essential for the success of this precedence-less type of cluster formation reaction.