Hidden Charge Order in an Iron Oxide Square-Lattice Compound.

Since the discovery of charge disproportionation in the FeO_{2} square-lattice compound Sr_{3}Fe_{2}O_{7} by Mössbauer spectroscopy more than fifty years ago, the spatial ordering pattern of the disproportionated charges has remained "hidden" to conventional diffraction probes, despite numerous x-ray and neutron scattering studies. We have used neutron Larmor diffraction and Fe K-edge resonant x-ray scattering to demonstrate checkerboard charge order in the FeO_{2} planes that vanishes at a sharp second-order phase transition upon heating above 332 K. Stacking disorder of the checkerboard pattern due to frustrated interlayer interactions broadens the corresponding superstructure reflections and greatly reduces their amplitude, thus explaining the difficulty of detecting them by conventional probes.

Zero-dimensional hybrid iodobismuthate derivatives: from structure study to photovoltaic application.

The quest for lead-free light-absorbing perovskite materials has long been the target of researchers to make the 'star' material friendly to the commercial market. After a summary of different lead-free solar absorbers, we demonstrate a zero-dimensional iodobismuthate (MA)[BiI]·3MACl (MA: CHNH) featuring isolated hexaiodobismuthate(iii) anions in the crystal analysis. The unexpectedly formed material was made via an orthogonal solvent permeation method and the decomposition of the guest solvent.

Using Predefined M(μ-O) Clusters as Building Blocks for an Isostructural Series of Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) have attracted much attention in the past decade owing to their unprecedented internal surface areas, tunable topologies, designable surfaces, and various potential applications. One bottleneck in the field regarding MOF synthesis is controlling the metal-containing secondary building unit (SBU) incorporated into the structure. In this work we report the synthesis and characterization of five trimeric [M(μ-O)(CHCO)] clusters (where M = Fe, Cr, Fe/Cr, Fe/Co, or Fe/Ni and x = +1 or 0).

The Intricate Structural Chemistry of ML-Type Assemblies.

The reaction of cis-blocked, square-planar M complexes with tetratopic N-donor ligands is known to give metallasupramolecular assemblies of the formula ML. These assemblies typically adopt barrel-like structures, with the ligands paneling the sides of the barrels. However, alternative structures are possible, as demonstrated by the recent discovery of a PtL cage with unusual gyrobifastigium-like geometry.

Crystal growth, structure and magnetic properties of CaCrO.

A detailed diffraction study of CaCrO is presented which adds significant new insights into the structural and magnetic properties of this compound. A new crystal structure type was used where the a and b axes are doubled compared to previous models providing a more plausible structure where all crystallographic sites are fully occupied. The presence of two different valences of chromium was verified and the locations of the magnetic Cr and non-magnetic Cr ions were identified.

Neutral Aminyl Radicals Derived from Azoimidazolium Dyes.

The synthesis and characterization of a new class of neutral aminyl radicals is reported. Monoradicals were obtained by reduction of azoimidazolium dyes with potassium. Structural, spectroscopic, and computational data suggest that the spin density is centered on one of the nitrogen atoms of the former azo group.

Dinuclear clathrochelate complexes with pendent cyano groups as metalloligands.

Dinuclear clathrochelate complexes with two, three, four, or five cyano groups in the ligand periphery were prepared following two distinct synthetic strategies: (a) zinc(ii)- or cobalt(ii)-templated polycondensation reactions of CN-functionalized arylboronic acids and phenoldioximes, or (b) postsynthetic cross-coupling reactions of polybrominated zinc(ii) clathrochelates with 4-cyanophenylboronic acid. The new clathrochelate complexes were used as metalloligands for the construction of heterometallic Zn/Ag and Co/Ag coordination polymers (CPs), which were characterized by single crystal X-ray diffraction and FT-IR. A one-dimensional CP was observed for ditopic clathrochelates, whereas two- and three-dimensional CPs were generated from tetra- and pentatopic metalloligands.

A new multipurpose diffractometer PILATUS@SNBL.

The diffraction beamline BM01A at the European Synchrotron Radiation Facility (CRG Swiss-Norwegian beamlines) has been successfully operational for 20 years. Recently, a new multifunctional diffractometer based on the Dectris Pilatus 2M detector has been constructed, commissioned and offered to users. The diffractometer combines a fast and low-noise area detector, which can be tilted and moved horizontally and vertically, together with flexible goniometry for sample positioning and orientation.

Surface functionalization of dinuclear clathrochelates via Pd-catalyzed cross-coupling reactions: facile synthesis of polypyridyl metalloligands.

Dinuclear clathrochelate complexes are easily accessible by reaction of zinc(ii) triflate or cobalt(ii) nitrate with arylboronic acids and phenoldioximes. The utilization of brominated arylboronic acids and/or brominated phenoldioximes allows preparing clathrochelates with two, three, five or seven bromine atoms on the outside. These clathrochelates can undergo Pd-catalyzed cross-coupling reactions with 3- and 4-pyridylboronic acid to give new metalloligands featuring up to seven pyridyl groups.

Carboxylic Acid Functionalized Clathrochelate Complexes: Large, Robust, and Easy-to-Access Metalloligands.

Polycarboxylate ligands are among the most important building blocks for the synthesis of metal-organic frameworks (MOFs). The ability to access these ligands in an efficient way is of key importance for future applications of MOFs. Here, we demonstrate that mono- and dinuclear clathrochelate complexes are versatile scaffolds for the preparation of polytopic carboxylate ligands.

Ligand Aspect Ratio as a Decisive Factor for the Self-Assembly of Coordination Cages.

It is possible to control the geometry and the composition of metallasupramolecular assemblies via the aspect ratio of their ligands. This point is demonstrated for a series of iron- and palladium-based coordination cages. Functionalized clathrochelate complexes with variable aspect ratios were used as rod-like metalloligands.

Crystal structures of eight mono-methyl alkanes (C26-C32) via single-crystal and powder diffraction and DFT-D optimization.

The crystal structures of eight mono-methyl alkanes have been determined from single-crystal or high-resolution powder X-ray diffraction using synchrotron radiation. Mono-methyl alkanes can be found on the cuticles of insects and are believed to act as recognition pheromones in some social species, e.g.

Serial snapshot crystallography for materials science with SwissFEL.

New opportunities for studying (sub)microcrystalline materials with small unit cells, both organic and inorganic, will open up when the X-ray free electron laser (XFEL) presently being constructed in Switzerland (SwissFEL) comes online in 2017. Our synchrotron-based experiments mimicking the 4%-energy-bandpass mode of the SwissFEL beam show that it will be possible to record a diffraction pattern of up to 10 randomly oriented crystals in a single snapshot, to index the resulting reflections, and to extract their intensities reliably. The crystals are destroyed with each XFEL pulse, but by combining snapshots from several sets of crystals, a complete set of data can be assembled, and crystal structures of materials that are difficult to analyze otherwise will become accessible.

Large, heterometallic coordination cages based on ditopic metallo-ligands with 3-pyridyl donor groups.

Ditopic N-donor ligands with terminal 4-pyridyl groups are omnipresent in coordination-based self-assembly. The utilization of ligands with 3-pyridyl donor groups is significantly less common, because the intrinsic conformational flexibility of these ligands tends to favor the formation of small aggregates. Here, we show that large PdL cages can be obtained by reaction of Pd(ii) salts with metallo-ligands L bearing terminal 3-pyridyl groups.

Structural investigation of the high spin→low spin relaxation dynamics of the porous coordination network [Fe(pz)Pt(CN)4]⋅2.6 H2O.

The Hoffman-type coordination compound [Fe(pz)Pt(CN)4]⋅2.6 H2O (pz = pyrazine) shows a cooperative thermal spin transition at around 270 K. Synchrotron powder X-Ray diffraction studies reveal that a quantitative photoinduced conversion from the low-spin (LS) state into the high-spin (HS) state, based on the light-induced excited spin-state trapping effect, can be achieved at 10 K in a microcrystalline powder.

Crystal structure and solution species of Ce(III) and Ce(IV) formates: from mononuclear to hexanuclear complexes.

Cerium(III) and cerium(IV) both form formate complexes. However, their species in aqueous solution and the solid-state structures are surprisingly different. The species in aqueous solutions were investigated with Ce K-edge EXAFS spectroscopy.

Homologous critical behavior in the molecular frameworks Zn(CN)2 and Cd(imidazolate)2.

Using a combination of single-crystal and powder X-ray diffraction measurements, we study temperature- and pressure-driven structural distortions in zinc(II) cyanide (Zn(CN)2) and cadmium(II) imidazolate (Cd(im)2), two molecular frameworks with the anticuprite topology. Under a hydrostatic pressure of 1.52 GPa, Zn(CN)2 undergoes a first-order displacive phase transition to an orthorhombic phase, with the corresponding atomic displacements characterized by correlated collective tilts of pairs of Zn-centered tetrahedra.

Crystal structure of the insect neuropeptide proctolin.

The crystal structure of the neuropeptide proctolin (Arg-Tyr-Leu-Pro-Thr) is reported revealing the solid-state conformation of its molecules and their association in the crystal.

Features of the secondary structure of a protein molecule from powder diffraction data.

Protein powder diffraction is shown to be suitable for obtaining de novo solutions to the phase problem at low resolution via phasing methods such as the isomorphous replacement method. Two heavy-atom derivatives (a gadolinium derivative and a holmium derivative) of the tetragonal form of hen egg-white lysozyme were crystallized at room temperature. Using synchrotron radiation, high-quality powder patterns were collected in which pH-induced anisotropic lattice-parameter changes were exploited in order to reduce the challenging and powder-specific problem of overlapping reflections.

Bulk homochirality of a 3-D inorganic framework: ligand control of inorganic network chirality.

Enantioselective synthesis of a 3-D inorganic net has been achieved leading to metal-organic frameworks built from cobalt-oxide helices in which handedness is controlled by the chirality of the linked ligand.

trans-Decahydronaphthalene (decalin) from powder diffraction data.

The title compound, C(10)H(18), a decalin stereoisomer, crystallizes with Z' = 0.5 in the space group P2(1)/n. The trans-decalin molecule is located on an inversion centre with both rings in a chair conformation, making for a quasi-flat overall shape.

Molecular dynamics study of tryptophylglycine: a dipeptide nanotube with confined water.

To investigate the mechanism of structural changes of a peptide nanotube and water confined inside the channel, the helical peptide tryptophylglycine monohydrate (WG.H2O) was studied by molecular dynamics (MD) simulations using the three-dimension parallel MD program ddgmq (software package) and a consistent force field. Simulations were performed on both the water-containing system and a model system without water molecules.

Photoluminescent microporous lanthanide silicate AV-21 frameworks.

The hydrothermal synthesis and structural characterization of the lanthanide silicate system [Na(6)Ln(2)Si(12)O(30).x H(2)O] (Ln=La(3+), Sm(3+), Eu(3+), Gd(3+), and Tb(3+)), named AV-21, has been reported. Structural elucidation of the Sm(3+) analogue (isomorphous with the Eu(3+), Gd(3+), and Tb(3+) frameworks) using single-crystal synchrotron X-ray diffraction and solid-state NMR spectroscopy reveal disorder in the Si(1) second coordination sphere.