Foreword to the AfCA collection: celebrating work published by African researchers in IUCr journals

This virtual collection is a celebration. It is a celebration of crystallography in Africa, and a celebration of the international crystallography community. It commemorates the founding of the African Crystallographic Association (AfCA), which was accepted as the newest Regional Associate of the International Union of Crystallography (IUCr) in 2023, the year of the 75th anniversary of the first IUCr Congress and General Assembly. The collection contains research articles authored by scientists across the African continent, as well as a selection of articles giving context to crystallography in Africa. These discuss history, collaboration between scientists and between associations, and various educational and outreach initiatives.

Synthesis, crystal structure, and Hirshfeld surface analysis of 1,3-di­hydro-2H-benzimidazol-2-iminium 3-carb­oxy-4-hy­droxy­benzene­sulfonate

The asymmetric unit of the title salt comprises two 1,3-di­hydro-2H-benzimidazol-2-iminium cations and two 2-hy­droxy-5-sulfobenzoate anions (Z′ = 2). In the crystal, the mol­ecules inter­act through N—H⋯O, O—H⋯O hydrogen bonds and C—O⋯π contacts. The hydrogen-bonding inter­actions lead to the formation of layers parallel to (01).

Color center creation by dipole stacking in crystals of 2-meth­oxy-5-nitro­aniline

The title compound 2-meth­oxy-5-nitro­aniline forms orange–red crystals and displays shifts in light absorption to longer wavelengths in solution as the concentration increases. Mol­ecular face-to-face stacking with dipoles oriented anti­parallel creates a color center, which is compared to certain inorganic semiconductors.

Mol­ecular structure of tris­[(6-bromo­pyridin-2-yl)meth­yl]amine

Crystals of tris­[(6-bromo­pyridin-2-yl)meth­yl]amine (TPABr₃) were obtained from a solution in aceto­nitrile upon evaporation. The crystals are triclinic with space group P.

Synthesis, crystal structure and Hirshfeld surface analysis of 4′-cyano-[1,1′-biphen­yl]-4-yl 3-(benz­yloxy)benzoate

The mol­ecules of the title compound are linked by weak C—H⋯O and C—H⋯π inter­actions.

Crystal structure, Hirshfeld surface analysis, DFT optimized mol­ecular structure and the mol­ecular docking studies of 1-[2-(cyano­sulfan­yl)acet­yl]-3-methyl-2,6-bis­(4-methyl­phen­yl)piperidin-4-one

In the title compound, C₂₃H₂₄N₂O₂S, the two mol­ecules in the asymmetric unit have a structural overlap with an r.m.s. deviation of 0.82 Å.

Crystal structure of bis­(μ₂-5-nona­noylquinolin-8-olato)bis­[aqua­dichlorido­indium(III)]

An analysis of the complex structure obtained by crystallization of 5-nona­noyl-8-hy­droxy­quinoline and InCl₃ in aceto­nitrile is reported.

Coupling between 2-pyridyl­selenyl chloride and phenyl­seleno­cyanate: synthesis, crystal structure and non-covalent inter­actions

The structure of a new seleno­diazo­lium salt derived from the reaction between 2-pyridyl­selenyl chloride and phenyl­seleno­cyanate is described. Halogen–hydrogen, chalcogen–chalcogen, chalcogen–hydrogen and chalcogen–halogen inter­actions are present in the structure.

Synthesis and crystal structure of poly[ethanol(μ-4-methyl­pyridine N-oxide)di-μ-thio­cyanato-cobalt(II)]

In the crystal structure of the title compound, the Co^II cations are octa­hedrally coordinated by two bridging and one terminal thio­cyanate anions, two bridging 4-methyl­pyridine N-oxide coligands and one ethanol mol­ecule and linked into chains by single μ-1,3-bridging anionic ligands that are further connected into layers by pairs of μ-1,1(O,O)-bridging 4-methyl­pyridine N-oxide coligands.

Crystal structure and Hirshfeld surface analysis of (E)-N-(2-styrylphen­yl)benzene­sulfonamide

The crystal structure of the title compound C₂₀H₁₇NO₂S features hydrogen-bonding and C—H⋯π. Docking studies show that it has a strong binding affinity with EGFR kinase, indicating its potential as a promising candidate for targeted lung cancer therapy.

Crystal structure and Hirshfeld surface analysis of tri­chlorido­(1,10-phenanthroline-κ²N,N′)phenyltin(IV)

The title compound, which was obtained by the reaction between 1,10-phenanthroline and phenyl­tin trichloride in methanol, exhibits intra­molecular inter­actions involving the chlorine and hydrogen atoms. Crystal cohesion is ensured by inter­molecular C—H⋯Cl hydrogen bonds, as well as Y—X⋯π and π-stacking inter­actions

Synthesis, non-spherical structure refinement and Hirshfeld surface analysis of racemic 2,2′-diisobut­oxy-1,1′-bi­naphthalene

The structure of the title 1–1′-binaphthyl derivative was refined with non-spherical atomic form factors computed using the DFT method at the PBE0/def2-TZVP basis set level.

8-Hy­droxy­quinolinium tri­chlorido­(pyridine-2,6-di­carb­oxy­lic acid-κ³O,N,O′)copper(II) dihydrate

The title compound, (C₉H₈NO)[CuCl₃(C₇H₅NO₄)]·2H₂O, was synthesized by reacting Cu^II acetate, 8-hy­droxy­quinoline, and pyridine-2,6-di­carb­oxy­lic acid in dilute hydro­chloric acid in a 1:1:1 molar ratio. The Cu^II atom exhibits a distorted octa­hedral geometry coordinated by the H₂pydc ligand and chloride atoms. In the crystal structure, various hydrogen bonds and weak inter­actions lead to the formation of a three-dimensional network.

Synthesis, characterization, and crystal structure of hexa­kis­(1-methyl-1H-imidazole-κN³)zinc(II) dinitrate

The title complex, which consists of a central zinc metal ion surrounded by six 1-methyl­imidazole ligands, charge balanced by two nitrate anions and which crystallizes in the space group P has been synthesized and its structure determined.

Synthesis and crystal structure of poly[[μ-chlorido-μ-(2,3-di­methyl­pyrazine)-copper(I)] ethanol hemisolvate], which shows a new isomeric CuCl(2,3-di­methyl­pyrazine) network

In the crystal structure of the title compound, the copper cations are each tetra­hedrally coordinated by two 2–3-di­methyl­pyrazine ligands and two chloride anions and linked into dinuclear units that are further connected into layers by bridging 2,3-di­methyl­pyrazine ligands.

Synthesis, crystal structure and Hirshfeld surface analysis of sulfamethoxazolium methyl­sulfate monohydrate

The title mol­ecular salt was prepared by the reaction of sulfamethoxazole and H₂SO₄ in methanol and crystallized from methanol–ether–water. Protonation takes place at the nitro­gen atom of the primary amino group. In the crystal, N—H⋯O hydrogen bonds (water and methyl­sulfate anion) and inter­molecular N—H⋯N inter­actions involving the sulfonamide and isoxazole nitro­gen atoms, link the components into a tri-dimensional network, which also features face-to-face π–π inter­actions between the phenyl rings of adjacent mol­ecules.

Crystal structure and supra­molecular features of a host–guest inclusion complex based on A1/A2-hetero-difunctionalized pillar[5]arene

The crystal structure of an A1/A2-bromo­but­oxy-hy­droxy difunctionalized pillar[5]arene that encapsulates an adipo­nitrile mol­ecule in its cavity is reported and the supra­molecular features of this inclusion complex are discussed.

Crystal structure, Hirshfeld surface analysis, and calculations of inter­molecular inter­action energies and energy frameworks of 1-[(1-hexyl-1H-1,2,3-triazol-4-yl)meth­yl]-3-(1-methyl­ethen­yl)-benzimidazol-2-one

In the title mol­ecule, the benzimidazole moiety is oriented almost perpendicular to the triazole ring. In the crystal, C—H⋯O hydrogen bonds link the mol­ecules into a network structure.

Crystal structure and Hirshfeld surface analysis of {2-[bis­(pyridin-2-ylmeth­yl)amino]­ethane-1-thiol­ato}­chlorido­cadmium(II)

A mononuclear cadmium(II) complex [CdLCl], where HL = 2-[bis­(pyridin-2-ylmeth­yl)amino]­ethane-1-thiol, was synthesized and characterized by single-crystal X-ray diffraction and Hirshfeld analysis.

Crystal structures of seven mixed-valence gold compounds of the form [(R¹R²R³PE)₂Au^I]⁺[Au^IIIX₄]⁻ (R = tert-butyl or iso­propyl, E = S or Se, and X = Cl or Br)

The ligands at the Au^I atoms are anti­periplanar to each other across the S⋯S vectors. Residues are linked by various contacts of the types C—H⋯X, E⋯X and Br⋯Br.

Structure of 2,3,5-tri­phenyl­tetra­zol-3-ium chloride hemi­penta­hydrate

The packing of the title hydrated mol­ecular salt features an unusual O—H⋯π inter­action.

Crystal structures of the (η²:η²-cyclo­octa-1,5-diene)(η⁶-toluene)­iridium(I) cation and μ-chlorido-iridium(III) complexes of 2-(phosphinito)- and 2-(phosphinometh­yl)anthra­quinone ligands

Phosphinito and phosphinomethyl ligands incorporating an anthra­quinone moiety were reacted with bis­(cyclo­octa-1,5-diene)diiridium(I) dichloride to afford novel diiridium species. Intended as pincer-type tridentate ligands, bidentate binding modes were determined by X-ray crystallography. The anionic μ-tri­chlorido phosphinito complex formed is charged-balanced by one [Ir(toluene)(cyclo­octa-1,5-diene)]⁺ per asymmetric unit, the structure of which has not previously been reported despite a long history of use as an Ir^I source in organometallic chemistry.