Combining forces: complementary techniques brought together to determine tricky crystal structures

Dudek and coworkers [Acta Cryst. (2020), B76, 322–335] report an integrated X-ray powder diffraction, NMR crystallography and crystal structure prediction study to determine crystal structures that could not have been determined using a single method. This is an important example that nicely illustrates the process of combining techniques and demonstrates the importance of careful validation.

TAAM: a reliable and user friendly tool for hydrogen-atom location using routine X-ray diffraction data

Transferable Aspherical Atom Model (TAAM) instead of Independent Atom Model (IAM) applied through DiSCaMB software library in the structure refinement against X-ray diffraction data largely improves the X—H bond lengths and make them comparable to the averaged neutron bond lengths.

Crystallization of chiral molecular compounds: what can be learned from the Cambridge Structural Database?

A study on chiral monomolecular compound structures found in the Cambridge Structural Database is presented.

The modulated low-temperature structure of malayaite, CaSnOSiO₄

The crystal structure of malayaite, CaSnOSiO₄, at T = 20 K has been refined, based on the presence of satellite reflections with a modulation vector of 0.26b*. The structural modulation is attributed to a soft optic phonon, dominated by motion of the Ca atoms.

Crystal structures of two furazidin polymorphs revealed by a joint effort of crystal structure prediction and NMR crystallography

Joint use of an NMR crystallography approach and crystal structure prediction calculations reveals the crystal structures of two previously uncharacterized polymorphs of furazidin.

A closer look at superionic phase transition in (NH₄)₄H₂(SeO₄)₃: impedance spectroscopy under pressure

The proton-conducting crystal (NH₄)₄H₂(SeO₄)₃ is examined to check whether its conductivity spectra and the phase transition to the superprotonic phase are sensitive to subtle changes in the crystal structure and proton dynamics caused by various thermodynamic conditions. It is established that the kinetics of this transformation can be described using the Avrami model with an effective Avrami index value associated with homogeneous nucleation and three-dimensional growth of a new phase.

The mechanism of solvent-mediated desolvation transformation of lenvatinib mesylate from di­methyl sulfoxide solvate to form D

The solvent-mediated desolvation process of newly discovered lenvatinib DMSO solvate to form II at different water volume fractions and temperatures was investigated. It is confirmed that the activity of water is the most important factor affecting the desolvation process: the desolvation process only occurs when the activity of water is greater than the activity of DMSO, and one new mechanism of solvent-mediated desolvation process was proposed.

Orientational disorder of mono­methyl-quinacridone investigated by Rietveld refinement, structure refinement to the pair distribution function and lattice-energy minimizations

The crystal structure of the nanocrystalline pigment mono­methyl-quinacridone was solved from X-ray powder data. The orientational disorder was investigated using Rietveld refinements, structure refinement to the pair distribution function, and lattice-energy minimizations of various ordered structural models.

Synthesis and crystallographic, spectroscopic and computational characterization of 3,3′,4,4′-substituted bi­phenyls: effects of OR substituents on the intra-ring torsion angle

The synthesis, characterization and study of structures from a series of bi­phenyls substituted at positions 3, 3′, 4 and 4′ with groups connected to the bi­phenyl core through oxygen atoms are presented here. The molecular conformation is extensively studied both in the solid as well as in the liquid state, and the effect of different factors (such as packing and chain length) on the torsion angle between aromatic rings is analyzed.

Structure variations within RSi₂ and R₂Si₃ silicides. Part II. Structure driving factors

Most articles dealing with RSi₂ and R₂TSi₃ compounds are only interested in one specific compound or in a series of compounds with varying T elements while keeping R fixed (or vice versa). Here, the focus lies on the complete space of 2:1:3 and 1:2 silicides, discussing various crystallographic properties and reasons for the formation of the different symmetries and superstructures.

A new Zn^II metallocryptand with unprecedented diflexure helix induced by V-shaped di­imidazole building blocks

A new Zn^II metallocryptand is presented, with an unprecedented diflexure helix.

Intra- and intermolecular interactions in a series of chlorido-tri­carbonyl-di­aza­butadienerhenium(I) complexes: structural and theoretical studies

A series of chlorido-tri­carbonylrhenium(I) complexes bearing alkyl-substituted N,N′-bis­(benzene)-1,4-di­aza­butadiene ligands were synthesized and structurally and spectroscopically characterized. The intra- and intermolecular interactions of the synthesized complexes were investigated by X-ray diffraction and detailed theoretical studies using the non-covalent interaction index and natural bond orbital methods.

Synthesis, crystal structure, polymorphism and microscopic luminescence properties of anthracene derivative compounds

Crystal structure and microscopic optical properties of anthracene derivative compounds have been investigated using single-crystal synchrotron X-ray diffraction, laser confocal microscopy and fluorescence lifetime imaging microscopy.

Structure-directing sulfur⋯metal noncovalent semicoordination bonding

Noncovalent contacts between sulfur atom and various transition metals are recognized and extensively studied using a combination of processing data from Cambridge Structural Database and theoretical calculations. The predominance of semicoordination bond character rather than chalcogen bonding is explored.

Charge density of 4-methyl-3-[(tetra­hydro-2H-pyran-2-yl)­oxy]thia­zole-2(3H)-thione. A comprehensive multipole refinement, maximum entropy method and density functional theory study

Static charge density representation using the multipole model and DFT is compared to the dynamic representation of the maximum entropy method. The hydroxyl­amine bond is put under a detailed spotlight. Hirshfeld atom refinement is compared to periodic calculations.

Prediction of orientation relationships and interface structures between α-, β-, γ-FeSi₂ and Si phases

Predictions of coherent interphase boundary orientations and atomic structures are carried out based on purely crystallogeometrical methods. Possible epitaxial interfaces are derived for α-, β, γ-FeSi₂ and Si phases to verify the proposed approach and show prospects of iron disilicide heterojunctions synthesis.

Joint crystallization of KCuAl[PO₄]₂ and K(Al,Zn)₂[(P,Si)O₄]₂: crystal chemistry and mechanism of formation of phosphate-silicate epitaxial heterostructure

New compounds, KCuAl[PO₄]₂ (I) and K(Al,Zn)₂[(P,Si)O₄]₂ (II), obtained hydrothermally, were studied by single-crystal X-ray diffraction. Based on its structure, (I) is a potentially electrochemically active material and/or possible low-temperature antiferromagnet. The phase (II) was established to be a product of epitaxial intergrowth of phosphate KAlZn[PO₄]₂ and silicate KAlSi[SiO₄]₂ components with close crystal structures, thus providing a single diffraction pattern.

Synthesis, structure and properties of layered Pr₂MoO₆-based oxymolybdates doped with Mg

Undoped and Mg-doped Pr₂MoO₆ oxymolybdate polycrystals and single crystals have been prepared by solid-state reactions and flux growth. The incorporation of Mg atoms into the structure of Pr₂MoO₆ results in the partial substitution of Mg atoms for Mo atoms and disordering of the praseodymium and oxygen lattices.

Hydrogen bonding in the crystal structure of phurcalite, Ca₂[(UO₂)₃O₂(PO₄)₂]·7H₂O: single-crystal X-ray study and TORQUE calculations

The crystal structure of the uranyl-phosphate mineral phurcalite is characterised by extensive hydrogen bonding. It comprises a less common type of H₂O bonding in solids: a transformer H₂O unit (with a three-coordinated O atom), which is not directly linked to any metal cation. This study documents the advantage of combining XRD data and TORQUE calculations, which are significantly less demanding of resources than DFT calculations..