The title compound, C20H16N2O2, is composed of two monosubstituted benzene rings and one benzimidazole unit. The benzimidazole moiety subtends dihedral angles of 46.16 (7) and 77.45 (8)° with the benzene rings, which themselves form a dihedral angle of 54.34 (9)°. The crystal structure features O—H⋯N and O—H⋯O hydrogen-bonding inter­actions, which together lead to the formation of two-dimensional hydrogen-bonded layers parallel to the (101) plane. In addition, π–π inter­actions also contribute to the crystal cohesion. Hirshfeld surface analysis indicates that the most significant contacts in the crystal packing are: H⋯H (47.5%), O⋯H/H⋯O (12.4%), N⋯H/H⋯N (6.1%), C⋯H/H⋯C (27.6%) and C⋯C (4.6%).

The title compound, [RuCl2(C33H43N3O)], is an example of a new generation of N,N-dialkyl ruthenium catalysts with an N—Ru coordination bond as part of a six-membered chelate ring. The Ru atom has an Addison τ parameter of 0.244, which indicates a geometry inter­mediate between square-based pyramidal and trigonal–bipyramidal. The complex shows the usual trans arrangement of the two chlorides, with Ru—Cl bond lengths of 2.3515 (8) and 2.379 (7) Å, and a Cl—Ru—Cl angle of 158.02 (3)°. One of the chlorine atoms and the atoms of the 2-meth­oxy-N-methyl-N-[(2-methyl­phen­yl)meth­yl]ethane-1-amine group of the title complex display disorder over two positions in a 0.889 (2): 0.111 (2) ratio.

The title complex, [ZnCl(C12H15N3O2)2][ZnCl3(CH3CN)], was synthesized and its structure was fully characterized through single-crystal X-ray diffraction analysis. The complex crystallizes in the ortho­rhom­bic system, space group Pbca (61), with a central zinc atom coordinating one chlorine atom and two pyrrolidinyl-4-meth­oxy­phenyl azoformamide ligands in a bidentate manner, utilizing both the nitro­gen and oxygen atoms in a 1,3-heterodiene (N=N—C=O) motif for coordinative bonding, yielding an overall positively (+1) charged complex. The complex is accompanied by a [(CH3CN)ZnCl3]− counter-ion. The crystal data show that the harder oxygen atoms in the heterodiene zinc chelate form bonding inter­actions with distances of 2.002 (3) and 2.012 (3) Å, while nitro­gen atoms are coordinated by the central zinc cation with bond lengths of 2.207 (3) and 2.211 (3) Å. To gain further insight into the inter­molecular inter­actions within the crystal, Hirshfeld surface analysis was performed, along with the calculation of two-dimensional fingerprint plots. This analysis revealed that H⋯H (39.9%), Cl⋯H/H⋯Cl (28.2%) and C⋯H/H⋯C (7.2%) inter­actions are dominant. This unique crystal structure sheds light on arrangement and bonding inter­actions with azo­formamide ligands, and their unique qualities over similar semicarbazone and azo­thio­formamide structures.

The asymmetric unit of the title compound, μ-biphenyl-4,4'-di­sulfonato-bis­(aqua­lithium), [Li2(C12H8O6S2)(H2O)2] or Li2[Bph(SO3)2](H2O)2, consists of an Li ion, half of the diphenyl-4,4'-di­sulfonate [Bph(SO3−)2] ligand, and a water mol­ecule. The Li ion exhibits a four-coordinate tetra­hedral geometry with three oxygen atoms of the Bph(SO3−)2 ligands and a water mol­ecule. The tetra­hedral LiO4 units, which are inter­connected by biphenyl moieties, form a layer structure parallel to (100). These layers are further connected by hydrogen-bonding inter­actions to yield a three-dimensional network.

The structures of 16 phosphane chalcogenide complexes of gold(I) halides, with the general formula R13-nR2nPEAuX (R1 = t-butyl; R2 = isopropyl; n = 0 to 3; E = S or Se; X = Cl, Br or I), are presented. The eight possible chlorido derivatives are: 1a, n = 3, E = S; 2a, n = 2, E = S; 3a, n = 1, E = S; 4a, n = 0, E = S; 5a, n = 3, E = Se; 6a, n = 2, E = Se; 7a, n = 1, E = Se; and 8a, n = 0, E = Se, and the corresponding bromido derivatives are 1b–8b in the same order. However, 2a and 2b were badly disordered and 8a was not obtained. The iodido derivatives are 2c, 6c and 7c (numbered as for the series a and b). All structures are solvent-free and all have Z' = 1 except for 6b and 6c (Z' = 2). All mol­ecules show the expected linear geometry at gold and approximately tetra­hedral angles P—E—Au. The presence of bulky ligands forces some short intra­molecular contacts, in particular H⋯Au and H⋯E. The Au—E bond lengths have a slight but consistent tendency to be longer when trans to a softer X ligand, and vice versa. The five compounds 1a, 5a, 6a, 1b and 5b form an isotypic set, despite the different alkyl groups in 6a. Compounds 3a/3b, 4b/8b and 6b/6c form isotypic pairs. The crystal packing can be analysed in terms of various types of secondary inter­actions, of which the most frequent are `weak' hydrogen bonds from methine hydrogen atoms to the halogenido ligands. For the structure type 1a, H⋯X and H⋯E contacts combine to form a layer structure. For 3a/3b, the packing is almost featureless, but can be described in terms of a double-layer structure involving borderline H⋯Cl/Br and H⋯S contacts. In 4a and 4b/8b, which lack methine groups, Cmeth­yl—H⋯X contacts combine to form layer structures. In 7a/7b, short C—H⋯X inter­actions form chains of mol­ecules that are further linked by association of short Au⋯Se contacts to form a layer structure. The packing of compound 6b/6c can conveniently be analysed for each independent mol­ecule separately, because they occupy different regions of the cell. Mol­ecule 1 forms chains in which the mol­ecules are linked by a Cmethine⋯Au contact. The mol­ecules 2 associate via a short Se⋯Se contact and a short H⋯X contact to form a layer structure. The packing of compound 2c can be described in terms of two short Cmethine—H⋯I contacts, which combine to form a corrugated ribbon structure. Compound 7c is the only compound in this paper to feature Au⋯Au contacts, which lead to twofold-symmetric dimers. Apart from this, the packing is almost featureless, consisting of layers with only translation symmetry except for two very borderline Au⋯H contacts.

In the structure of the title compound, C19H19N3O5S·C4H8O2, the two independent dioxane mol­ecules each display inversion symmetry. The pyrazole ring is approximately parallel to the aromatic ring of the oxy-ethanone group and approximately perpendicular to the tolyl ring of the sulfonyl substituent. An extensive system of classical and `weak' hydrogen bonds connects the residues to form a layer structure parallel to (201), within which dimeric subunits are conspicuous; neighbouring layers are connected by classical hydrogen bonds to dioxanes and by `weak' hydrogen bonds from Htol­yl donors.

This paper summarizes brief perspectives on the historic process of establishing an African Crystallographic Association (AfCA) and includes representative references. It covers activities within four arbitrarily selected, approximate time slots, i.e., 1890s–1999, 2000–2013, 2014–2019 and 2020–2023. A genuine attempt is made to include appropriate role players, organizations and accompanying events within these periods. It concludes with the official admission of AfCA as the fifth Regional Associate of the IUCr at the 26th Congress and General Assembly of the IUCr in Melbourne, Australia in 2023.

In the title compound, C25H25NO7S, the mol­ecular conformation is stabilized by intra­molecular O—H⋯O and N—H⋯O hydrogen bonds, which form S(6) and S(8) ring motifs, respectively. The mol­ecules are bent at the S atom with a C—SO2—NH—C torsion angle of −70.86 (11)°. In the crystal, mol­ecules are linked by C—H⋯O and N—H⋯O hydrogen bonds, forming mol­ecular layers parallel to the (100) plane. C—H⋯π inter­actions are observed between these layers.

In the title compound, C20H18N2S, the asymmetric unit comprises two similar mol­ecules (A and B). In mol­ecule A, the central thio­phene ring makes dihedral angles of 89.96 (12) and 57.39 (13)° with the 1H-pyrrole rings, which are bent at 83.22 (14)° relative to each other, and makes an angle of 85.98 (11)° with the phenyl ring. In mol­ecule B, the corresponding dihedral angles are 89.49 (13), 54.64 (12)°, 83.62 (14)° and 85.67 (11)°, respectively. In the crystal, mol­ecular pairs are bonded to each other by N—H⋯N inter­actions. N—H⋯π and C—H⋯π inter­actions further connect the mol­ecules, forming a three-dimensional network. A Hirshfeld surface analysis indicates that H⋯H (57.1% for mol­ecule A; 57.3% for mol­ecule B), C⋯H/H⋯C (30.7% for mol­ecules A and B) and S⋯H/H⋯S (6.2% for mol­ecule A; 6.4% for mol­ecule B) inter­actions are the most important contributors to the crystal packing.

In the title compound, C18H22O7, two hexane rings and an oxane ring are fused together. The two hexane rings tend toward a distorted boat conformation, while the tetra­hydro­furan and di­hydro­furan rings adopt envelope conformations. The oxane ring is puckered. The crystal structure features C—H⋯O hydrogen bonds, which link the mol­ecules into a three-dimensional network. According to a Hirshfeld surface study, H⋯H (60.3%) and O⋯H/H⋯O (35.3%) inter­actions are the most significant contributors to the crystal packing.

At room temperature, the title salt, C7H10NO+·Cl−, is ortho­rhom­bic, space group Pbca with Z' = 1, as previously reported [Zhao (2009). Acta Cryst. E65, o2378]. Between 250 and 200 K, there is a solid-state phase transition to a twinned monoclinic P21/c structure with Z' = 2. We report the high temperature structure at 250 K and the low-temperature structure at 100 K. In the low-temperature structure, the –NH3 hydrogen atoms are ordered and this group has a different orientation in each independent mol­ecule, in keeping with optimizing N—H⋯Cl hydrogen bonding, some of which are bifurcated: these hydrogen bonds have N⋯Cl distances in the range 3.1201 (8)–3.4047 (8) Å. In the single cation of the high-temperature structure, the NH hydrogen atoms are disordered into the average of the two low-temperature positions and the N⋯Cl hydrogen bond distances are in the range 3.1570 (15)–3.3323 (18) Å. At both temperatures, the meth­oxy group is nearly coplanar with the rest of the mol­ecule, with the C—C—O—C torsion angles being −7.0 (2)° at 250 K and −6.94 (12) and −9.35 (12)° at 100 K. In the extended ortho­rhom­bic structure, (001) hydrogen-bonded sheets occur; in the monoclinic structure, the sheets propagate in the (010) plane.

Syntheses of the acyclic amidinium salts, morpholino­formamidinium hexa­fluorido­phosphate [OC4H8N—CH=NH2]PF6 or C5H11N2O+·PF6−, 1, and pyrrolidinoformamidinium hexa­fluorido­phosphate [C4H8N—CH= NH2]PF6 or C5H11N2+·PF6−, 2, were carried out by heating either morpholine or pyrrolidine with triethyl orthoformate and ammonium hexa­fluorido­phosphate. Crystals of 1 obtained directly from the reaction mixture contain one cation and one anion in the asymmetric unit. The structure involves cations linked in chains parallel to the b axis by N—H⋯O hydrogen bonds in space group Pbca, with glide-related chains pointing in opposite directions. Crystals of 1 obtained by recrystallization from ethanol, however, showed a similar unit cell and the same basic structure, but unexpectedly, there was positional disorder [occupancy ratio 0.639 (4):0.361 (4)] in one of the cation chains, which lowered the crystal symmetry to the non-centrosymmetric space group Pca21, with two cations and anions in the asymmetric unit. In the pyrrolidino compound, 2, cations and anions are ordered and are stacked separately, with zigzag N—H⋯F hydrogen-bonding between stacks, forming ribbons parallel to (101), extended along the b-axis direction. Slight differences in the delocalized C=N distances between the two cations may reflect the inductive effect of the oxygen atom in the morpholino compound.

JUAMI, the joint undertaking for an African materials institute, is a project to build collaborations and materials research capabilities between PhD researchers in Africa, the United States, and the world. Focusing on research-active universities in the East African countries of Kenya, Ethiopia, Tanzania and Uganda, the effort has run a series of schools focused on materials for sustainable energy and materials for sustainable development. These bring together early-career researchers from Africa, the US, and beyond, for two weeks in a close-knit environment. The program includes lectures on cutting-edge research from internationally renowned speakers, highly interactive tutorial lectures on the science behind the research, also from internationally known researchers, and hands-on practicals and team-building exercises that culminate in group proposals from self-formed student teams. The schools have benefited more than 300 early-career students and led to proposals that have received funding and have led to research collaborations and educational non-profits. JUAMI continues and has an ongoing community of alumni who share resources and expertise, and is open to like-minded people who want to join and develop contacts and collaborations internationally.

The reaction of the Schiff base 2-[1-(pyridin-2-yl)ethyl­idene­amino]­ethanol (HL), which is formed by reaction of 2-amino­ethanol and 2-acetyl­pyridine with CuBr2 in ethanol results in the isolation of the new polymeric complex poly[hexa-μ-bromido-bis­{2-[1-(pyridin-2-yl)ethyl­idene­amino]­ethano­lato}tetra­copper(II)], [Cu4Br6(C9H11N2O)2]n or [Cu4Br6L2]n. The asymmetric unit of the crystal structure of the polymeric [Cu4Br6L2]n complex is composed by four copper (II) cations, two monodeprotonated mol­ecules of the ligand, and six bromide anions, which act as bridges. The ligand mol­ecules act in a tridentate fashion through their azomethine nitro­gen atoms, their pyridine nitro­gen atoms, and their alcoholate O atoms. The crystal structure shows two types of geometries in the coordination polyhedrons around Cu2+ ions. Two copper cations are situated in a square-based pyramidal environment, while the two other copper cations adopt a tetra­hedral geometry. Bromides anions acting as bridges between two metal ions connect the units, resulting in a tetra­nuclear polymer compound.

In the title compound, C20H18O4, the dihedral angle between the 2H-chromen-2-one ring system and the phenyl ring is 89.12 (5)°. In the crystal, the mol­ecules are connected through C—H⋯O hydrogen bonds to generate [010] double chains that are reinforced by weak aromatic π–π stacking inter­actions. The unit-cell packing can be described as a tilted herringbone motif. The H⋯H, H⋯O/O⋯H, H⋯C/C⋯H and C⋯C contacts contribute 46.7, 24.2, 16.7 and 7.6%, respectively, to its Hirshfeld surface.

The title compound, C10H11N5O2S2, consists of an unexpected tautomer with a protonated nitro­gen atom in the triazine ring and a formal exocyclic double bond C=N to the sulfonamide moiety. The ring angles at the unsubstituted nitro­gen atoms are narrow, at 115.57 (12) and 115.19 (12)°, respectively, whereas the angle at the carbon atom between these N atoms is very wide, 127.97 (13)°. The inter­planar angle between the two rings is 79.56 (5)°. The mol­ecules are linked by three classical hydrogen bonds, forming a ribbon structure. There are also unusual linkages involving three short contacts (< 3 Å) from a sulfonamide oxygen atom to the C—NH—C part of a triazine ring.

In the title compound, C10H8N4O3·C3H7NO, the asymmetric unit contains two crystallographically independent mol­ecules A and B, each of which has one DMF solvate mol­ecule. Mol­ecules A and B both feature intra­molecular N—H⋯O hydrogen bonds, forming S(6) ring motifs and consolidating the mol­ecular configuration. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds connect mol­ecules A and B, forming R22(8) ring motifs. Weak C—H⋯O inter­actions link the mol­ecules, forming layers parallel to the (overline{2}12) plane. The DMF solvent mol­ecules are also connected to the main mol­ecules (A and B) by N—H⋯O hydrogen bonds. π–π stacking inter­actions [centroid-to-centroid distance = 3.8702 (17) Å] between the layers also increase the stability of the mol­ecular structure in the third dimension. According to the Hirshfeld surface study, O⋯H/H⋯O inter­actions are the most significant contributors to the crystal packing (27.5% for mol­ecule A and 25.1% for mol­ecule B).

The synthesis and crystallographic analysis of the title compound, C9H9N3O2S, are reported. The compound crystallizes in the monoclinic space group P21/c, revealing characteristic bond lengths and angles typical of thio­semicarbazone groups. The supra­molecular organization primarily arises from hydrogen bonding and π–π stacking inter­actions, leading to distinctive dimeric formations.

The asymmetric unit of the title compound, catena-poly[[[aqua­bis­(pyridine-κN)cadmium(II)]-μ2-4,4'-(1H-1,2,4-triazole-3,5-di­yl)dibenzoato-κ4O,O':O'',O'''] 4.5-hydrate], {[Cd(C16H9N3O4)(C5H5N)2(H2O)]·4.5H2O}n or {[Cd(bct)(py)2(H2O)]·4.5H2O}n (I), consists of a Cd2+ cation coordinated to one bct2– carboxyl­ate dianion, two mol­ecules of pyridine and a water mol­ecule as well as four and a half water mol­ecules of crystallization. The metal ion in I possesses a penta­gonal–bipyramidal environment with the four O atoms of the two bidentately coordinated carboxyl­ate groups and the N atom of a pyridine mol­ecule forming the O4N equatorial plane, while the N atom of another pyridine ligand and the O atom of the water mol­ecule occupy the axial positions. The bct2– bridging ligand connects two metal ions via its carb­oxy­lic groups, resulting in the formation of a parallel linear polymeric chain running along the [1overline{1}1] direction. The coordinated water mol­ecule of one chain forms a strong O—H⋯O hydrogen bond with the carboxyl­ate O atom of a neighboring chain, leading to the formation of double chains with a closest distance of 5.425 (7) Å between the cadmium ions belonging to different chains. Aromatic π–π stacking inter­actions between the benzene fragments of the anions as well as between the coordinated pyridine mol­ecules belonging to different chains results in the formation of sheets oriented parallel to the (overline{1}01) plane. As a result of hydrogen-bonding inter­actions involving the water mol­ecules of crystallization, the sheets are joined together in a three-dimensional network.

The title compound, C16H11N2OF, is a member of the azo dye family. The dihedral angle subtended by the benzene ring and the naphthalene ring system measures 18.75 (7)°, indicating that the compound is not perfectly planar. An intra­molecular N—H⋯O hydrogen bond occurs between the imino and carbonyl groups. In the crystal, the mol­ecules are linked into inversion dimers by C—H⋯O inter­actions. Aromatic π–π stacking between the naphthalene ring systems lead to the formation of chains along [001]. A Hirshfeld surface analysis was undertaken to investigate and qu­antify the inter­molecular inter­actions. In addition, energy frameworks were used to examine the cooperative effect of these inter­molecular inter­actions across the crystal, showing dispersion energy to be the most influential factor in the crystal organization of the compound.

The title complex, [Au(NCO)(C27H36N2)], was synthesized by ligand metathesis from [1,3-bis­(2,6-diiso­propyl­phen­yl)imidazol-2-yl­idene]gold(I) chloride and sodium cyanate in anhydrous tetra­hydro­furan and crystallized from toluene at 233 K in the ortho­rhom­bic space group P212121, as a neutral complex with the central Au atom di-coordinated by an N-heterocyclic carbene [Au—C = 1.963 (2) Å] and an iso­cyanate [Au—N 1.999 (2) Å] ligands, with a linear CAuNCO moiety. The crystal packing is consolidated by C—H⋯O hydrogen bonds.

The title com­pound, C13H11NO, adopts an E configuration about the C=C double bond. The pyrrole ring is inclined to the phenyl ring at an angle of 44.94 (8)°. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, forming ribbons parallel to (020) in zigzag C(7) chains along the a axis. These ribbons are connected via C—H⋯π inter­actions, forming a three-dimensional network. No significant π–π inter­actions are observed.

The reaction of Co(NCS)2 with 4-methyl­pyridine N-oxide (C6H7NO) leads to the formation of two compounds, namely, tetra­kis­(4-methyl­pyridine N-oxide-κO)bis­(thio­cyanato-κN)cobalt(II), [Co(NCS)2(C6H7NO)4] (1), and tris­(4-methyl­pyridine N-oxide-κO)bis­(thio­cyanato-κN)cobalt(II), [Co(NCS)2(C6H7NO)3] (2). The asymmetric unit of 1 consists of one CoII cation located on a centre of inversion, as well as one thio­cyanate anion and two 4-methyl­pyridine N-oxide coligands in general positions. The CoII cations are octa­hedrally coordinated by two terminal N-bonding thio­cyanate anions in trans positions and four 4-methyl­pyridine N-oxide ligands. In the extended structure, these complexes are linked by C—H⋯O and C—H⋯S inter­actions. In compound 2, two crystallographically independent complexes are present, which occupy general positions. In each of these complexes, the CoII cations are coordinated in a trigonal–bipyramidal manner by two terminal N-bonding thio­cyanate anions in axial positions and by three 4-methyl­pyridine N-oxide ligands in equatorial positions. In the crystal, these complex mol­ecules are linked by C—H⋯S inter­actions. For compound 2, a nonmerohedral twin refinement was performed. Powder X-ray diffraction (PXRD) reveals that 2 was nearly obtained as a pure phase, which is not possible for compound 1. Differential thermoanalysis and thermogravimetry data (DTA–TG) show that compound 2 start to decompose at about 518 K.

In the title benzyl­ideneaniline Schiff base, C18H22N2O, the aromatic rings are inclined to each other by 46.01 (6)°, while the Car—N= C—Car torsion angle is 176.9 (1)°. In the crystal, the only identifiable directional inter­action is a weak C—H⋯π hydrogen bond, which generates inversion dimers that stack along the a-axis direction.

The (S)-(+)-1-(4-bromo­phen­yl)-N-[(4-methoxyphen­yl)methyl­idene]ethyl­amine ligand, C16H16BrNO, (I), was synthesized through the reaction of 4-meth­oxy­anisaldehyde with (S)-(−)-1-(4-bromo­phen­yl)ethyl­amine. It crystallizes in the ortho­rhom­bic space group P212121 belonging to the Sohncke group, featuring a single mol­ecule in the asymmetric unit. The refinement converged successfully, achieving an R factor of 0.0508. The PdII com­plex bis­{(S)-(+)-1-(4-bromo­phen­yl)-N-[(4-methoxyphen­yl)methyl­idene]ethyl­amine-κN}di­chlorido­pal­ladium(II), [PdCl2(C16H16BrNO)2], (II), crystallizes in the monoclinic space group P21 belonging to the Sohncke group, with two mol­ecules in the asymmetric unit. The central atom is tetra­coordinated by two N atoms and two Cl atoms, resulting in a square-planar configuration. The imine moieties exhibit a trans configuration around the PdII centre, with average Cl—Pd—N angles of approximately 89.95 and 90°. The average distances within the palladium com­plex for the two mol­ecules are ∼2.031 Å for Pd—N and ∼2.309 Å for Pd—Cl.

The crystal structures and Hirshfeld surface analyses of three similar azo compounds are reported. Methyl 4-{2,2-di­chloro-1-[(E)-phenyl­diazen­yl]ethen­yl}benzoate, C16H12Cl2N2O2, (I), and methyl 4-{2,2-di­chloro-1-[(E)-(4-methyl­phen­yl)diazen­yl]ethen­yl}benzoate, C17H14Cl2N2O2, (II), crystallize in the space group P21/c with Z = 4, and methyl 4-{2,2-di­chloro-1-[(E)-(3,4-di­methyl­phen­yl)diazen­yl]ethen­yl}benzoate, C18H16Cl2N2O2, (III), in the space group Poverline{1} with Z = 2. In the crystal of (I), mol­ecules are linked by C—H⋯N hydrogen bonds, forming chains with C(6) motifs parallel to the b axis. Short inter­molecular Cl⋯O contacts of 2.8421 (16) Å and weak van der Waals inter­actions between these chains stabilize the crystal structure. In (II), mol­ecules are linked by C—H⋯O hydrogen bonds and C—Cl⋯π inter­actions, forming layers parallel to (010). Weak van der Waals inter­actions between these layers consolidate the mol­ecular packing. In (III), mol­ecules are linked by C—H⋯π and C—Cl⋯π inter­actions forming chains parallel to [011]. Furthermore, these chains are connected by C—Cl⋯π inter­actions parallel to the a axis, forming (0overline{1}1) layers. The stability of the mol­ecular packing is ensured by van der Waals forces between these layers.

The title compound, C16H17N3O3, is racemic as it crystallizes in a centrosymmetric space group (Poverline{1}), although the trans disposition of substituents about the central C—C bond is established. The five- and six-membered rings are oriented at a dihedral angle of 75.88 (8)°. In the crystal, N—H⋯N hydrogen bonds form chains of mol­ecules extending along the c-axis direction that are connected by inversion-related pairs of O—H⋯N into ribbons. The ribbons are linked by C—H⋯π(ring) inter­actions, forming layers parallel to the ab plane. A Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯H (45.9%), H⋯N/N⋯H (23.3%), H⋯C/C⋯H (16.2%) and H⋯O/O⋯H (12.3%) inter­actions. Hydrogen bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. The volume of the crystal voids and the percentage of free space were calculated to be 100.94 Å3 and 13.20%, showing that there is no large cavity in the crystal packing. Evaluation of the electrostatic, dispersion and total energy frameworks indicates that the stabilization is dominated by the electrostatic energy contributions in the title compound. Moreover, the DFT-optimized structure at the B3LYP/6–311 G(d,p) level is compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

The in­do­line portion of the title mol­ecule, C16H13NO2, is planar. In the crystal, a layer structure is generated by C—H⋯O hydrogen bonds and C—H⋯π(ring), π-stacking and C=O⋯π(ring) inter­actions. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (43.0%), H⋯C/C⋯H (25.0%) and H⋯O/O⋯H (22.8%) inter­actions. Hydrogen bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. The volume of the crystal voids and the percentage of free space were calculated to be 120.52 Å3 and 9.64%, respectively, showing that there is no large cavity in the crystal packing. Evaluation of the electrostatic, dispersion and total energy frameworks indicate that the stabilization is dominated by the dispersion energy contributions in the title compound. Moreover, the DFT-optimized structure at the B3LYP/6-311G(d,p) level is compared with the experimentally determined mol­ecular structure in the solid state.

The title compound, C27H20N4O3S, crystallizes in the monoclinic system, space group P21/n, with Z = 4. The global shape of the mol­ecule is determined by the orientation of the substituents on the central 4H-1,2,4-triazole ring. The nitro­phenyl ring, phenyl ring, and naphthalene ring system are oriented at dihedral angles of 82.95 (17), 77.14 (18) and 89.46 (15)°, respectively, with respect to the triazole ring. The crystal packing features chain formation in the b-axis direction by S⋯O inter­actions. A Hirshfeld surface analysis indicates that the highest contributions to surface contacts arise from contacts in which H atoms are involved.

The title compound [systematic name: 1-(2-nitro­phen­yl)pyrrole-2,5-dione], C10H6N2O4, crystallizes in the monoclinic system (space group P21/n) with two mol­ecules in the asymmetric unit, which are linked by C—H⋯O hydrogen bonds. Hirshfeld surface analysis showed that the most significant contributions to the crystal packing are from H⋯O/O⋯H, H⋯C/C⋯H and H⋯H inter­actions, which contribute 54.7%, 15.2% and 15.6%, respectively. A DFT study was conducted using three different levels of theory [(B3LYP/6–311+G(d,p), wB97XD/Def2TZVPP and LC-wpbe/6–311(2 d,2p)] in order to determine the stability, structural and electronic properties of the title mol­ecule with a view to its potential applications and photochemical and copolymer properties.

The reaction between 2-pyridyl­selenenyl chloride and isobutyro­nitrile results in the formation of the corresponding cationic pyridinium-fused 1,2,4-seleno­diazole, namely, 3-(propan-2-yl)-1,2,4-[1,2,4]selena­diazolo[4,5-a]pyridin-4-ylium chloride, C9H11N2Se+·Cl−, in high yield (89%). The structure of the compound, established by means of single-crystal X-ray analysis at 100 K, has monoclinic (P21/c) symmetry and revealed the presence of bifurcated chalcogen-hydrogen bonding Se⋯Cl−⋯H—Cl, and these non-covalent contacts were analysed by DFT calculations followed by a topological analysis of the electron-density distribution (ωB97XD/6-311++G** level of theory).

The title mol­ecule, [Fe2(C5H5)2(C23H17ClN2)]·C3H7NO, is twisted end to end and the central N/C/N unit is disordered. In the crystal, several C—H⋯π(ring) inter­actions lead to the formation of layers, which are connected by further C—H⋯π(ring) inter­actions. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (60.2%) and H⋯C/C⋯H (27.0%) inter­actions. Hydrogen bonding, C—H⋯π(ring) inter­actions and van der Waals inter­actions dominate the crystal packing.

Two compounds, (S)-8-{[(tert-butyl­dimethyl­sil­yl)­oxy]meth­yl}-1-[(2,2,4,6,7-penta­methyl-2,3-di­hydro­benzo­furan-5-yl)sulfon­yl]-1,3,4,6,7,8-hexa­hydro-2H-pyrimido[1,2-a]pyrimidin-1-ium tri­fluoro­methane­sulfonate, C27H46N3O4SSi+·CF3O3S−, (1) and (S)-8-(iodo­meth­yl)-1-tosyl-1,3,4,6,7,8-hexa­hydro-2H-pyrimido[1,2-a]pyrimidin-1-ium iodide, C15H21IN3O2S+·I−, (2), have been synthesized and characterized. They are bicyclic guanidinium salts and were synthesized from N-(tert-but­oxy­carbon­yl)-l-me­thio­nine (Boc-l-Met-OH). The guanidine is protected by a 2,2,4,6,7-penta­methyl­dihydro­benzo­furan-5-sulfonyl (Pbf, 1) or a tosyl (2) group. In the crystals of both compounds, the guanidinium group is almost planar and the N–H forms an intra­molecular hydrogen bond in a six-membered ring to the oxygen atom of the sulfonamide protecting group.

The crystal structures and Hirshfeld surface analyses of three similar compounds are reported. Methyl 4-[4-(di­fluoro­meth­oxy)phen­yl]-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexa­hydro­quinoline-3-carboxyl­ate, (C21H23F2NO4), (I), crystallizes in the monoclinic space group C2/c with Z = 8, while isopropyl 4-[4-(di­fluoro­meth­oxy)phen­yl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexa­hydro­quinoline-3-carb­oxyl­ate, (C23H27F2NO4), (II) and tert-butyl 4-[4-(di­fluoro­meth­oxy)phen­yl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexa­hydro­quinoline-3-carboxyl­ate, (C24H29F2NO4), (III) crystallize in the ortho­rhom­bic space group Pbca with Z = 8. In the crystal structure of (I), mol­ecules are linked by N—H⋯O and C—H⋯O inter­actions, forming a tri-periodic network, while mol­ecules of (II) and (III) are linked by N—H⋯O, C—H⋯F and C—H⋯π inter­actions, forming layers parallel to (002). The cohesion of the mol­ecular packing is ensured by van der Waals forces between these layers. In (I), the atoms of the 4-di­fluoro­meth­oxy­phenyl group are disordered over two sets of sites in a 0.647 (3): 0.353 (3) ratio. In (III), the atoms of the dimethyl group attached to the cyclo­hexane ring, and the two carbon atoms of the cyclo­hexane ring are disordered over two sets of sites in a 0.646 (3):0.354 (3) ratio.

In the title compound, C12H11N3OS, the inter­planar angle between the pyrazole and benzo­thia­zole rings is 3.31 (7)°. In the three-dimensional mol­ecular packing, the carbonyl oxygen acts as acceptor to four C—H donors (with one H⋯O as short as 2.25 Å), while one methyl hydrogen is part of the three-centre system H⋯(S, O). A double layer structure parallel to (overline{1}01) can be recognized as a subsection of the packing.

A CuII coordination polymer, catena-poly[[[aqua­copper(II)]-bis­(μ-4-amino­benz­o­ato)-κ2N:O;κ2O:N] monohydrate], {[Cu(pABA)2(H2O)]·H2O}n (pABA = p-amino­benzoate, C7H4NO2−), was synthesized and characterized. It exhibits a one-dimensional chain structure extended into a three-dimensional supra­molecular assembly through hydrogen bonds and π–π inter­actions. While the twinned crystal shows a metrically ortho­rhom­bic lattice and an apparent space group Pbcm, the true symmetry is monoclinic (space group P2/c), with disordered Cu atoms and mixed roles of water mol­ecules (aqua ligand/crystallization water). The luminescence spectrum of the complex shows an emission at 345 nm, cf. 349 nm for pABAH.

An attempt to explore the reactivity of the nitro group in the presence of gold catalysis in comparison to the azide group yielded intriguing results. Surprisingly, only the nitro group exhibited reactivity, ultimately giving rise to the formation of the title isatogen, C14H8N4O2. In the crystal structure, weak C—H⋯O hydrogen bonds and π–π stacking inter­actions link the mol­ecules. The structure exhibits disorder of the mol­ecule.

In the title compound, C31H24N4O2, the quinoxaline units are distinctly non-planar and twisted end-to-end. In the crystal, C—H⋯O and C—H⋯N hydrogen bonds link the mol­ecules into chains extending along the a-axis direction. The chains are linked through π-stacking inter­actions between inversion-related quinoxaline moieties.

The neutral organosilicon(IV) complex, (C6F5)2Si(OPO)2 (OPO = 1-oxopyridin-2-one, C5H4NO2), was synthesized from (C6F5)2Si(OCH3)2 and 2 equiv. of 1-hy­droxy­pyridin-2-one in tetra­hydro­furan (THF). Single crystals grown from the diffusion of n-pentane into a THF solution were identified as a THF hemisolvate and an n-pentane hemisolvate, (C6F5)2Si(OPO)2·0.5THF·0.5C5H12 (1). p-Tol­yl2Si(OPO)2 (2) and mesit­yl2Si(OPO)2 (3) crystallized directly from reaction mixtures of 2 equiv. of Me3Si(OPO) with p-tol­yl2SiCl2 and mesit­yl2SiCl2, respectively, in aceto­nitrile. The oxygen-bonded carbon and nitro­gen atoms of the OPO ligands in 1, 2, and 3 were modeled as disordered indicating co-crystallization of up to three possible diastereomers in each. Solution NMR studies support the presence of exclusively the all-cis isomer in 1 and multiple isomers in 2. Poor solubility of 3 limited its characterization in solution.

The title compound, C14H12N2O4, was obtained from 2-acetyl-6-amino­naphthalene through two-step reactions of acetyl­ation and nitration. The mol­ecule comprises the naphthalene ring system consisting of functional systems bearing a acetyl group (C-2), a nitro group (C-5), and an acetyl­amino group (C-6). In the crystal, the mol­ecules are assembled into two-dimensional sheet-like structures by inter­molecular N—H⋯O and C—H⋯O hydrogen-bonding inter­actions. Hirshfeld surface analysis illustrates that the most important contributions to the crystal packing are from O⋯H/H⋯O (43.7%), H⋯H (31.0%), and C⋯H/H⋯C (8.5%) contacts.

In the title compound, C21H15N5OS2, mol­ecular pairs are linked by N—H⋯N hydrogen bonds along the c-axis direction and C—H⋯S and C—H⋯O hydrogen bonds along the b-axis direction, with R22(12) and R22(16) motifs, respectively, thus forming layers parallel to the (10overline{4}) plane. In addition, C=S⋯π and C≡N⋯π inter­actions between the layers ensure crystal cohesion. The Hirshfeld surface analysis indicates that the major contributions to the crystal packing are H⋯H (43.0%), C⋯H/H⋯C (16.9%), N⋯H/H⋯N (11.3%) and S⋯H/H⋯S (10.9%) inter­actions.

Metal complexes of 3,5-diiso­propyl­salicylate are reported to have anti-inflammatory and anti-convulsant activities. The title binuclear copper complex, [Cu2(C13H17O3)4(C2H6OS)2] or [Cu(II)2(3,5-DIPS)4(DMSO)2], contains two five-coordinate copper atoms that are bridged by four 3,5-diiso­propyl­salicylate ligands and capped by two axial dimethyl sulfoxide (DMSO) moieties. Each copper atom is attached to four oxygen atoms in an almost square-planar fashion, with the addition of a DMSO ligand in an apical position leading to a square-pyramidal arrangement. The hy­droxy group of the diiso­propyl­salicylate ligands participates in intra­molecular O—H⋯O hydrogen-bonding inter­actions.

Since its founding in 2013, the Young Crystallographers (YC) have become one of the most active working groups not only within their parent organization, the German Crystallographic Society (DGK), but also among other young crystallographers' groups in Europe and the world. The aim of the YC is and always has been to support early-career researchers in the diverse fields of crystallography and the rejuvenation of the field on a national scale. Over the past decade, we have curated events, platforms, and educational content tailored to foster collaboration and knowledge transfer among young crystallographers. In this article, we introduce our group and show how this active and diverse community has shaped the rejuvenation of crystallography in Germany, strengthened by the support of our national society.

The title compound, C25H18N4, crystallizes in the centrosymmetric ortho­rhom­bic space group Pbca, with eight mol­ecules in the unit cell. The main feature noticeable in the structure is the impact of the tri­cyano­vinyl (TCV) group in forcing partial planarity of the portion of the mol­ecule carrying the TCV group and directing the mol­ecular packing in the solid state, resulting in the formation of π-stacks of dimers within the unit cell. Short π–π stack closest atom-to-atom distances of 3.444 (15) Å are observed. Such motif patterns are favorable as they are thought to be conducive for better charge transport in organic semiconductors, which results in enhanced device performance. Intra­molecular charge transfer is evident from the shortening in the observed experimental bond lengths. The nitro­gen atoms (of the cyano groups) are involved in extensive short contacts, primarily through C—H⋯NC inter­actions with distances of 2.637 (17) Å.

The complex, tri­chlorido­(1,4,11-tri­aza-8-azonia­tetra­cyclo­[6.6.2.04,16.011,15]hexa­decane 1-oxide-κO)zinc(II) monohydrate, [ZnCl3(C12H23N4O)]·H2O, (I), has monoclinic symmetry (space group P21/n) at 120 K. The zinc(II) center adopts a slightly distorted tetra­hedral coordination geometry and is coordinated by three chlorine atoms and the oxygen atom of the oxidized tertiary amine of the tetra­cycle. The amine nitro­gen atom, inside the ligand cleft, is protonated and forms a hydrogen bond to the oxygen of the amine oxide. Additional hydrogen-bonding inter­actions involve the protonated amine, the water solvate oxygen atom, and one of the chloro ligands.

The structure of (S)-5-(3-acetyl-5-chloro-2-ethoxy-6-fluorophenyl)-2-oxazolidinone, C13H13ClFNO4, at 100 K has monoclinic (P21) symmetry. The compound has a polymeric structure propagated by a screw axis parallel to the b axis with N—H⋯O hydrogen bonding. It is of inter­est with respect to efforts in the synthesis of a candidate anti­cancer drug, parsaclisib.

The structures of ten phosphane chalcogenide complexes of gold(III) halides, with general formula R13–nR2nPEAuX3 (R1 = t-butyl; R2 = i-propyl; n = 0 to 3; E = S or Se; X = Cl or Br) are presented. The eight possible chlorido derivatives are: 9a, n = 3, E = S; 10a, n = 2, E = S; 11a, n = 1, E = S; 12a, n = 0, E = S; 13a, n = 3, E = Se; 14a, n = 2, E = Se; 15a, n = 1, E = Se; and 16a, n = 0, E = Se, and the corresponding bromido derivatives are 9b–16b in the same order. Structures were obtained for 9a, 10a (and a second polymorph 10aa), 11a (and its deutero­chloro­form monosolvate 11aa), 12a (as its di­chloro­methane monosolvate), 14a, 15a (as its deutero­chloro­form monosolvate 15aa, in which the solvent mol­ecule is disordered over two positions), 9b, 11b, 13b and 15b. The structures of 11a, 15a, 11b and 15b form an isotypic set, and those of compounds 10aa and 14a form an isotypic pair. All structures have Z' = 1. The gold(III) centres show square-planar coordination geometry and the chalcogenide atoms show approximately tetra­hedral angles (except for the very wide angle in 12a, probably associated with the bulky t-butyl groups). The bond lengths at the gold atoms are lengthened with respect to the known gold(I) derivatives, and demonstrate a considerable trans influence of S and Se donor atoms on a trans Au—Cl bond. Each compound with an isopropyl group shows a short intra­molecular contact of the type C—Hmethine⋯Xcis; these may be regarded as intra­molecular ‘weak’ hydrogen bonds, and they determine the orientation of the AuX3 groups. The mol­ecular packing is analysed in terms of various short contacts such as weak hydrogen bonds C—H⋯X and contacts between the heavier atoms, such as X⋯X (9a, 10aa, 11aa, 15aa and 9b), S⋯S (10aa, 11a and 12a) and S⋯Cl (10a). The packing of the polymorphs 10a and 10aa is thus quite different. The solvent mol­ecules take part in C—H⋯Cl hydrogen bonds; for 15aa, a disordered solvent region at z ≃ 0 is observed. Structure 13b involves unusual inversion-symmetric dimers with Se⋯Au and Se⋯Br contacts, further connected by Br⋯Br contacts.

The title compound, C14H12N4O2·0.5HCl·H2O or H(C14H12N4O2)2+·Cl−·2H2O, arose from the unexpected cyclization of isonicotinoyl-N-phenyl hydrazine carbo­thio­amide catalysed by cobalt(II) acetate. The organic mol­ecule is almost planar and a symmetric N⋯H+⋯N hydrogen bond links two of them together, with the H atom lying on a crystallographic twofold axis. The extended structure features N—H⋯O and O—H⋯Cl hydrogen bonds, which generate [001] chains. Weak C—H⋯Cl inter­actions cross-link the chains. The chloride ion has site symmetry 2. The major contributions to the Hirshfeld surface are from H⋯H (47.1%), Cl⋯H/H⋯Cl (total 10.8%), O⋯H/H⋯O (7.4%) and N⋯H/H⋯N (6.7%) inter­actions.

A lutetium(III) complex based on the anion of the ligand dimethyl (2,2,2-tri­chloro­acet­yl)phospho­ramidate (HL) and tetra­phenylphosphonium, of composition PPh4[LuL4] (L = CAPh = carbacyl­amido­phosphate), or (C24H20)[Lu(C4H6Cl3NO4P)4], has been synthesized and structurally characterized. The X-ray diffraction study of the compound revealed that the lutetium ion is surrounded by four bis-chelating CAPh ligands, forming the complex anion [LuL4]− with a coordination number of 8[O] for LuIII, while PPh4+ serves as a counter-ion. The coordination geometry around the Lu3+ ion was determined to be a nearly perfect triangular dodeca­hedron. The complex crystallizes in the monoclinic crystal system, space group P21/c, with four mol­ecules in the unit cell. Weak hydrogen bonds O⋯HC(Ph), Cl⋯HC(Ph) and N⋯HC(Ph) are formed between the cations and anions. For a comparative study, HL-based structures were retrieved from the Cambridge Structural Database (CSD) and their geometries and conformations are discussed. A Hirshfeld surface analysis was also performed.

The asymmetric unit of the title compound, 2C31H28N2O4S·C2H6O, contains a parent mol­ecule and a half mol­ecule of ethanol solvent. The main compound stabilizes its mol­ecular conformation by forming a ring with an R12(7) motif with the ethanol solvent mol­ecule. In the crystal, mol­ecules are connected by C—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional network. In addition, C—H⋯π inter­actions also strengthen the mol­ecular packing.