First bent form for the hydroxo-bridged cis-diammineplatinum(II) dimer [Pt₂(NH₃)₄(μ-OH)₂](ClO₄)₂

A perchlorate salt of the hydroxo-bridged cis-diammineplatinum(II) dimer has been shown to possess a bent structure in which two Pt coordination planes within the dinuclear cation are tilted at an angle of 151.7 (1)° to one another.

New view of the high-pressure behaviour of GdFeO₃-type perovskites

In this contribution we use the bond-valence concept to develop a model that predicts the relative compressibilities of the cation sites in oxide perovskites. This model, based only upon room-pressure bond lengths and bond-valence parameters, correctly predicts the structural behaviour and some physical properties of the oxide perovskites that have been measured at high pressure.

Mg_1 + xIr_1 − x (x = 0, 0.037 and 0.054), a binary intermetallic compound with a new orthorhombic structure type determined from powder and single-crystal X-ray diffraction

The crystal structure of a new binary intermetallic compound Mg_1 + xIr_1 − x (x = 0–0.054) with 25 atoms in the asymmetric unit was independently characterized by the high-resolution synchrotron powder and single-crystal X-ray diffraction methods.

Structural study of Cu_2−xSe alloys produced by mechanical alloying

The crystalline structures of the superionic high-temperature copper selenides Cu_2−xSe (0 < x < 0.25) produced using mechanical alloying were investigated using X-ray diffraction (XRD) and Rietveld refinements before and after heat treatment at 473 K for 90 h.

30 Space-group corrections: two examples of false polymorphism and one of incorrect interpretation of the fine details of an IR spectrum

Some 30 crystal structures that were originally described in space groups of unnecessarily low symmetry are revised. The new space groups reveal two false polymorphs and one incorrect interpretation of the fine details of the IR spectrum.

Non-aromatic endocyclic angle at the ring fusion with the aromatic ring in benzo­cyclopentene and -hexene, revisited

In benzocyclopentene the shortening of the bond length between the aromatic ring C atom and the C atoms directly attached to it depends on the hybridization of the latter atoms. Moreover, if only one of these atoms is sp² hybridized the non-aromatic endocyclic angle at this side is smaller.

A new polymorph of ortho-eth­oxy-trans-cinnamic acid: single-to-single-crystal phase transformation and mechanism

The α-polymorph of ortho-ethoxy-trans-cinnamic acid undergoes a reversible single–single phase transformation at 333 K, which was correlated with small changes in molecular conformation. Crystals of the new α′-phase could be stabilized at room temperature by irradiating with UV light for 6 h.

Photodimerization of the α′-polymorph of ortho-eth­oxy-trans-cinnamic acid in the solid state. I. Monitoring the reaction at 293 K

Irradiation of the α′-polymorph of ortho-ethoxy-trans-cinnamic acid with UV light results in a photodimerization reaction at only one of the two possible reaction sites. The final product crystal, corresponding to a 66.7% conversion, retains several hydrogen-bonding features of the original monomer crystal.

Packing conflicts in the Z′ = 5 structure of CF₃(CF₂)₃(CH₂)₁₀COOH

Electronic effects favor the spatial segregation of the CF₂, CH₂ and COOH regions in crystals of CF₃(CF₂)₃(CH₂)₁₀COOH, but that segregation hinders the dense and uniform filling of space. A high-Z′, modulated structure is the result.

Structural phase transitions, and Br⋯N and Br⋯Br interactions in 1-phenyl-2-methyl-4-nitro-5-bromo­imidazole

The crystals of C₁₀H₈N₃O₂Br undergo two reversible phase transitions between 295 and 100 K. Very similar crystal packing is observed in the three phases; it is determined mainly by halogen C—Br⋯N bonding and Br⋯Br intermolecular interactions.

Packing-dependent photochromism: the case of photoinduced intramolecular proton transfer in 6-(2′,4′-di­nitro­benzyl)-2,2′-bi­pyridine

A comparison of the structures of three polymorphic crystals of the title compound shows that the photochromic activity of ortho-nitrobenzylpyridines is closely related to the rotational freedom of the ortho-nitro group in the crystalline lattice.

Methods of crystallochemical analysis of supramolecular complexes by means of Voronoi–Dirichlet polyhedra: a study of cucurbituril host–guest compounds

Crystallochemical analysis methods with Voronoi–Dirichlet polyhedra are adjusted for supramolecular complexes of any complexity. Using these methods volumes and shapes are assessed for cucurbit[n]uril receptors (n = 5–10) and their cavities; a number of potential substrates are found which can optimally fit the cavities inside the cucurbit[5]uril and cucurbit[6]uril molecules.