Themed collection International Year of Crystallography Celebration: Europe and South Africa

Welcome to this CrystEngComm themed issue celebrating the 2014 International Year of Crystallography in Europe and South Africa.

N-Methylacetamide, a well-known peptide bond model, and dihalotetrafluorobenzenes form co-crystals and show geometrically orthogonal hydrogen and halogen bonds sharing the same carbonyl oxygen atom.

A new calix[4]arene-supported Mn^IIIMn^II cluster assembles in a layered manner through halogen interactions; structural and magnetic properties of this new cluster are presented.

A series of related MOFs built from the rigid tetrahedral H₄ttps ligand with Mn(II), Cu(II) or Cd(II) metal based nodes exhibiting rare fluorite or garnet topologies have been synthesised and characterised and are compared to one another.

This work focuses on caffeine and its ability to form cocrystals with dicarboxylic acids, considering the relative solubilities of both components rather than their stoichiometric ratio.

Tolfenamic acid (HTA) is a drug characterized by very poor solubility in water. By mechanochemical methods, new solid-state forms of HTA were obtained, showing better thermal stability than pure HTA and an improved dissolution rate.

A study of the potential of melamine to form layers in crystal structures of its solvates, co-crystals and salts.

The solid state behaviour of 1,1,4,4-tetraphenyl-1,3-butadiene (TPB), a well-known blue luminescent molecule, is presented. The crystal structures of four polymorphs and one solvate form are discussed and the experimental occurrence of the four polymorphs is rationalized.

[Ni(medpt)(NO₂)(η²-ONO)] displays an equilibrium between the η¹-NO₂ and the η¹-ONO linkage isomers between 150–298 K; upon photoactivation at 100 K the percentage of the η¹-ONO isomer increases.

Propylated cyclotriveratrylene ligands with N-donor groups form coordination polymers where the propyl groups aggregate or form a Pd₆L₄ cage.

Low-pressure CH₃Br polymorph α is governed by Br⋯Br bonds and is isostructural with CH₃I crystals. Above 1.5 GPa CH₃Br transforms to phase β, composed of interweaved C–H⋯Br bonded network isostructural with that in solid CH₃Cl. Electrostatic matching and close packing favour the C–H⋯Br bonds, competing with Br⋯Br contacts. Both types of CH₃X (X = Cl, Br, I) structures approximate the isostructural X₂ crystals.

Six new Ca(II) adducts with cytosine (cyt), cytidine (H₂cyd) and cytidine 5′-monophosphate (CMP) are presented. H₂cyd and CMP show unprecedented binding sites for the calcium ion.

The magnetic properties of a series of copper(II)–phenylmalonate complexes are tuned by the pyridine-type coligand.

Small but important: the kind of solvent added in liquid-assisted grinding syntheses of cocrystals influences the final product and the reaction rate.

This amino acid derived (red&blue) π-stacked (green) hydrogen bonded (striped) dimer forms a pcu-net with water molecules in the narrow channels. Four related molecules are also presented and all were subjected to graph set and Hirshfeld surface analyses.

Amino acids are efficient cocrystal formers towards the compounds that contain a carboxyl group: among levetiracetam, S-naproxen, S-oxiracetam, and S-diprophylline, only S-naproxen yielded cocrystals.

An exhaustive study of the nature of the C–Cl⋯Cl–C interactions found in crystals has been carried out at the MP2/aug-cc-pVDZ level using model dimers and a set of 45 dimers with Cl⋯Cl distances in the 2.75–4 Å range.

An experimental and computational study of the polymorphism of o-nitrophenyldiphenylphosphine oxide (1) has been carried out raising the question of why the anti polymorphs, more stable than the observed syn conformations according to our computations, have not been found.

A multidisciplinary study of the transformations and structure property relationships of creatine polymorphs and creatine monohydrate.

Higher uptake of longer chain alcohol vapours by a flexible 2D Zn-framework 1 is attributed to C–H⋯π interactions with hydrophobic channel walls.

Three-dimensional [CuX(TAA)]_n (X = Br (1), I (2)) and bi-dimensional [AgX(TAA)]_n (X = Cl (3), Br (4)) coordination polymers have been isolated by the direct synthesis from copper(I) and silver(I) halides and thioacetamide (TAA).

The persistence of the acid⋯amide heterodimer and the effect of methyl substitution on the short strong O–H⋯O hydrogen bond is investigated in urea and methylurea di-carboxylic acid molecular complexes. Temperature dependent structural changes are also reported utilising X-ray and neutron diffraction in tandem.

[GeBr₂{o-C₆H₄(PMe₂)₂}] undergoes a phase transition, involving a change in the aromatic⋯aromatic interface.

The combination of a glycine-derivative supramolecular salt with lanthanide(III) chloride hydrates under hydrothermal conditions (120 °C, 48 h) produced a family of isotypical materials formulated as [Ln(bodt)(Hbodt)].