Introduction to the special issue on halogen bonding

The Guest Editors of the special issue, Mate Erdelyi and Pierangelo Metrangolo, introduce a collection of papers presented at the 2nd International Symposium on Halogen Bonding.

Directional O⋯F halogen bonds

Comment on article by Sirohiwal et al. [Acta Cryst. (2017), B73, 140–152] in this special issue on halogen bonding.

Coordination chemistry of anions through halogen-bonding interactions

The paper by Szell et al. [Acta Cryst. (2017), B73, 153–162] in this special issue devoted to halogen bonding illustrates recent developments associated with this interaction in crystal engineering, unravelling here unusual trends of a coordination chemistry of halide anions.

Characterization of fluorine-centred `F⋯O' σ-hole interactions in the solid state

We report the experimental observation of a `unique' and `rare' F⋯O interaction, involving two electronegative atoms, having the characteristics of `short interatomic distance' and `high directionality' that provide robustness to the crystal packing. The characterization of these F⋯O contacts via different computational procedures establish the interaction to be dispersive in nature and the mutual polarization of an O atom by F and vice versa provides real physical insights into the role of atomic polarizability in interacting atoms in molecules in crystals.

1,3,5-Tri(iodoethynyl)-2,4,6-tri­fluoro­benzene: halogen-bonded frameworks and NMR spectroscopic analysis

Single-crystal X-ray diffraction structures are reported for a series of seven halogen-bonded cocrystals featuring 1,3,5-tris(iodoethynyl)-2,4,6-trifluorobenzene as the halogen-bond donor, and bromide ions (as ammonium or phosphonium salts) as the halogen-bond acceptors. Detailed NMR analyses (in solution and in the solid state) of this halogen-bond donor are also presented.

A new tecton with parallel halogen-bond donors: a path to supramolecular rectangles

A new tecton, 1,8-diiodoethynylanthracene, with two halogen-bond donor sites was synthesized and characterized. This tecton is capable of forming two parallel halogen bonds at once, which makes it a useful building block for the construction of a variety of supramolecular squares and rectangles.

Taking the halogen bonding–hydrogen bonding competition one step further: complexes of di­fluoro­iodo­methane with tri­methyl­phosphine, di­methyl sulfide and chloro­methane

The halogen bonding–hydrogen bonding competition revisited.

Cyclic networks of halogen-bonding interactions in molecular self-assemblies: a theoretical N—X⋯N versus C—X⋯N investigation

Molecular self-assembly driven by halogen bonds is reported. A combination of inter- and intramolecular halogen bonds can be utilized to design supramolecular networks containing a periodic array of cyclic halogen-bonding interactions.

The evaluation of QM/MM-driven molecular docking combined with MM/GBSA calculations as a halogen-bond scoring strategy

The combination of quantum mechanics/molecular mechanics-driven (QM/MM) docking with MM/GBSA (generalized-Born/surface area) scoring was used to reproduce protein–ligand experimental geometries with halogen bonding. This combination outperformed the Glide SP and XP scoring functions, as well as the recently published approach of dedicated halogen bonding.

Theoretical insights into the π-hole interactions in the complexes containing tri­phosphorus hydride (P₃H₃) and its derivatives

The π-hole of triphosphorus hydride (P₃H₃) and its derivatives Z₃X₃ (Z = P, As; X = H, F, Cl, Br) were discovered. The relative π-hole interactions belong to the closed-shell noncovalent interaction and the stabilization mainly results from electrostatic energy.

Experimental investigation of halogen-bond hard–soft acid–base complementarity

Investigation of halogen-bond hard–soft acid–base complementarity in solution and solid-phases is presented.

Cocrystal assembled by 1,4-di­iodo­tetra­fluoro­benzene and pheno­thiazine based on C—I⋯π/N/S halogen bond and other assisting interactions

The yellow cocrystal was assembled by 1,4-diiodotetrafluorobenzene and non-planar phenothiazine with a butterfly shape mainly by C—I⋯π, C—I⋯N and C—I⋯S halogen bonds. The cocrystal emits weak phosphorescence and relatively strong delayed fluorescence.

Testing the tools for revealing and characterizing the iodine–iodine halogen bond in crystals

The manifestation of atomic electron density anisotropy along and across the iodine–iodine halogen bond in organic polyiodide crystals is elucidated in terms of the Laplacian of electron density, one-electron potential and electron localization function.

Halogen bonding stabilizes a cis-azo­benzene derivative in the solid state: a crystallographic study

We show by single-crystal X-ray diffraction studies and computational analysis that halogen bonding can stabilize a metastable cis-azobenzene derivative in the solid state.

Utilizing bifurcated halogen-bonding interactions with the uranyl oxo group in the assembly of a UO₂–3-bromo-5-iodo­benzoic acid coordination polymer

The supramolecular assembly of a new crystalline uranyl 3-bromo-5-iodobenzoic acid coordination polymer displaying unique bifurcated halogen–oxo interactions is described, and the vibrational and luminescent spectroscopic manifestations thereof have been explored.

Crystallographic insights into the structural aspects of thioctic acid based halogen-bond donor for the functionalization of gold nanoparticles

The aim of this research is to perform a complete structural description of a new halogen bonding (XB) donor, which will be used for the surface functionalization of gold nanoparticles (AuNPs). Crystallographic studies of simple model systems will be used to determine the recognition capabilities of the synthesized XB donor, and the functionalization of the AuNPs with the XB donor and their solubility profile in different solvents will be described.

Color-tunable phosphorescence of 1,10-phenanthrolines by 4,7-methyl/-di­phenyl/-di­chloro substituents in cocrystals assembled via bifurcated C—I⋯N halogen bonds using 1,4-di­iodo­tetra­fluoro­benzene as a bonding donor

A series of phosphorescence cocrystals was successfully constructed from 1,4-diiodotetrafluorobenzene (1,4-DITFB) and 4,7-dimethyl-/4,7-diphenyl-/4,7-dichloro-1,10-phenanthroline (DMPhe, DPPhe, DClPhe) via C—I⋯N halogen bonding.

Relationships between hydrogen bonds and halogen bonds in biological systems

The competitive and orthogonal relationships between halogen bonds and the more ubiquitous hydrogen bond are reviewed, focusing on how these affect the structure of biological molecules and protein–ligand complexes.

Nature of E₂X₂ σ(4c–6e) of the X---E—E---X type at naphthalene 1,8-positions and model, elucidated by X-ray crystallographic analysis and QC calculations with the QTAIM approach

The nature of E₂X₂ σ(4c–6e) of the X---E—E---X type in 1-(8-XC₁₀H₆)E–E(C₁₀H₆X-8′)-1′ [(1) E, X = S, Cl; (2) S, Br; (3) Se, Cl; (4) Se, Br] is elucidated with quantum theory of atoms in molecules (QTAIM) after structural determination of (1), (3) and (4). In the case of E---X, the nature of a typical-hydrogen bond (t-HB) with no covalency is predicted for (1) and (3), a t-HB with covalency is predicted for (4), and the t-HB seems intermediate for (2).

Incommensurately modulated twin structure of nyerereite Na_1.64K_0.36Ca(CO₃)₂

The incommensurately modulated twin structure of nyerereite Na_1.64K_0.36Ca(CO₃)₂ has been first determined and then compared with the modulated structure of γ-Na₂CO₃.

Temperature-induced first-order displacive phase transition of isonicotinamide-4-methoxybenzoic acid co-crystal

This paper describes the molecular displacement of the hydrogen-bonded array as the driving force of the observed structural phase transition in isonicotinamide–4-methoxybenzoic acid co-crystal at T_c = 142.5 (5) K.

A potential Cu/V-organo­phosphonate platform for tailored void spaces via terpyridine mold casting

A potential Cu/V-organophosphonate platform for tailored void spaces via terpyridine mold casting is reported.

Variable-temperature structural studies on valence tautomerism in cobalt bis­(dioxolene) molecular complexes

Thermal valence tautomerism in the cobalt-bis(dioxolene) molecular complexes is evaluated using variable-temperature crystal structure studies. In the present study, the effects of lattice solvent and substitution of halogens on the pyridine ligand to the valence tautomerism are demonstrated in cobalt bis­(dioxolene) molecular complexes.

Triclinic crystal structure distortion of multiferroic BiMn₇O₁₂

The paper describes the triclinic distortion of multiferroic BiMn₇O₁₂. The anisotropic hkl-dependent peak shape by spherical harmonics was used to model crystal structure distortion at room temperature and below, and the distortion analysis was successfully performed using the ISODISTORT program.

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50 Years of Materials Science in Singapore