The crystal structure of a sodium iron-sulfur nitrosyl cluster salt, namely, catena-poly[[[diaquasodium(I)]-di-μ-aqua-[diaquasodium(I)]-di-μ-aqua] bis{heptanitrosyltri-μ3-sulfido-tetrairon(3 Fe-Fe)] dihydrate], {[Na2(H2O)8][Fe4S3(NO)7]2·2H2O}n, was determined by single-crystal X-ray diffraction. The crystal belongs to the orthorhombic system, space group Pna21. The structure retains the typical [Fe4S3(NO)7]- incomplete cubane-type core skeleton and its geometric configuration is similar to those of reported alkali metal Roussin's black salts, such as the caesium salt. Owing to the strong hydration effect of Na+, one-dimensional polymeric hydrated sodium chains extending along the a axis and a supramolecular network are formed via coordination and O-H...O hydrogen bonds with the water molecules. The crystal packing is primarily driven by this hydrogen-bonded network, accompanied by localized positional disorder of the lattice water molecules and a 60° rotational disorder of the anions around a pseudo-threefold axis. By introducing an inversion twin model and applying appropriate geometric and displacement parameter restraints, these crystallographic disorders were properly handled during the refinement.
The ternary Zintl arsenide Eu5Ga2As6 and two members of the Ba5In2As6-xSbx [x = 0.49 (2) and 2.92 (2)] solid solution series were obtained from Pb-flux reactions and characterized by single-crystal X-ray diffraction methods. They adopt the uncommon Sr5Al2Sb6 structure type and represent the first As-bearing compounds adopting this structure type. The polyanionic substructure consists of 1D chains of edge- and corner-sharing [TrPn4] (Tr = Ga, In; Pn = As, Sb) tetrahedra extending along the [100] direction, with pendant [Pn2] dumbbells. Non-random As/Sb site preferences within the polyanionic substructure of Ba5In2As6-xSbx are also discussed. Formal electron counting supports valence-precise Zintl notation for all reported compositions. First-principles electronic structure calculations for Eu5Ga2As6 reveal a moderate indirect band gap of ∼0.8 eV. Comparative calculations for the chemically related Eu3GaAs3 phase, also isolated during the present study, predict a narrow direct band gap of ∼0.2 eV and provide additional context for the bonding and electronic structure of Eu5Ga2As6.
Fucoxanthin (C42H58O6) is a highly functionalized allenic epoxy xanthophyll containing hydroxy, acetoxy, ketone and conjugated polyene units. Although its constitution and stereochemistry had been established by chemical, spectroscopic and synthetic studies, its small-molecule single-crystal X-ray structure has remained unavailable. Moss reported in 1979 [Pure Appl. Chem. (1979), 51, 507-514] that an early X-ray study by G. M. Sheldrick had reached only a partial solution of the fucoxanthin structure and that refinement had stalled at R ≃ 25%. The first small-molecule single-crystal X-ray structure of fucoxanthin has now been determined as the diethyl ether monosolvate, C42H58O6·C4H10O, at 100 K in the space group P1 using synchrotron radiation (λ = 0.4132 Å). The asymmetric unit contains two crystallographically independent fucoxanthin molecules and two diethyl ether molecules. The structure defines the relative stereochemistry, allene geometry, epoxide geometry, polyene bond-length alternation and solvate-assisted packing of fucoxanthin, and provides an independent small-molecule metrical reference for comparison with protein-bound fucoxanthin ligands.
An azo-azomethine-pyrazole hybrid, namely, 2-({[3-tert-butyl-1-(4-nitrophenyl)-1H-pyrazol-5-yl]imino}methyl)-4-[(4-methylphenyl)diazenyl]phenol, C27H26N6O3, crystallizes as an extended donor-π-acceptor system that combines azo, azomethine and pyrazole fragments within an almost coplanar conjugated framework. Single-crystal XRD revealed two crystallographically independent molecules (M1 and M2) in the asymmetric unit (Z' = 2), with small conformational differences arising mainly from the orientation variations of the peripheral substituents. In both molecules, an intramolecular O-H...N(imine) hydrogen bond generates an S(6) motif that reinforces molecular planarity and π-electron delocalization. The crystal packing is dominated by heterogeneous M1...M2 contacts, whereas the homologous M1...M1 and M2...M2 interactions are comparatively less effective. C-H...O and C-H...N hydrogen bonds, complemented by π-related contacts, assemble the molecules into a three-dimensional supramolecular architecture. The Hirshfeld surface analysis identifies H...H, C...H/H...C, O...H/H...O and N...H/H...N contacts as the principal contributors to the intermolecular organization. A Quantum Theory of Atoms in Molecules (QTAIM) analysis confirmed the intramolecular O-H...N(imine) interaction through the corresponding bond critical point and associated topological descriptors and also confirmed that a secondary intramolecular C-H...N(imine) contact forms a nonplanar S(6) motif. The FT-IR, 1H NMR and mass spectrometric data support the proposed molecular structure. The combined crystallographic, Hirshfeld surface and QTAIM analyses demonstrate the co-operative influence of hydrogen bonding and weak noncovalent interactions on the conformational stabilization and supramolecular assembly of this conjugated azo-azomethine-pyrazole system.
Thallium salts of weakly coordinating anions are common reagents in organometallic chemistry for generating reactive cationic species via salt metathesis. Despite their frequent use, their composition is often ambiguous due to cocrystallized solvents, rendering well-characterized solvent-free structures rare. Herein, we report the synthesis, crystal structure and thermal properties of truly solvent-free thallium(I) tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, Tl[BC 32 H 12 F 24 ], as determined by single-crystal X-ray diffraction (SC-XRD), powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA). The structure features short Tl...F contacts and a complex supramolecular architecture that is closely related to disorder and tilting of the anion arene rings, which generate distinct intermolecular interaction motifs. Key features include a herringbone arrangement of nonclassical C—H...F hydrogen bonds and a `fluorous' interlayer defined by F...F and C—F...π contacts. This leads to hinge-like networks in the structure, depending on the tilt of the arene rings. These features are associated with anisotropic thermal expansion, with significantly greater expansion along the crystallographic a and b axes, as inferred from PXRD measurements. In agreement with the solvent-free structure determined by SC-XRD, TGA confirms that the bulk material is solvent-free.
The crystal structure of a sodium iron–sulfur nitrosyl cluster salt, namely, catena -poly[[[diaquasodium(I)]-di-μ-aqua-[diaquasodium(I)]-di-μ-aqua] bis{heptanitrosyltri-μ 3 -sulfido-tetrairon(3 Fe — Fe )] dihydrate], {[Na 2 (H 2 O) 8 ][Fe 4 S 3 (NO) 7 ] 2 ·2H 2 O} n , was determined by single-crystal X-ray diffraction. The crystal belongs to the orthorhombic system, space group Pna 2 1 . The structure retains the typical [Fe 4 S 3 (NO) 7 ] − incomplete cubane-type core skeleton and its geometric configuration is similar to those of reported alkali metal Roussin's black salts, such as the caesium salt. Owing to the strong hydration effect of Na + , one-dimensional polymeric hydrated sodium chains extending along the a axis and a supramolecular network are formed via coordination and O—H...O hydrogen bonds with the water molecules. The crystal packing is primarily driven by this hydrogen-bonded network, accompanied by localized positional disorder of the lattice water molecules and a 60° rotational disorder of the anions around a pseudo-threefold axis. By introducing an inversion twin model and applying appropriate geometric and displacement parameter restraints, these crystallographic disorders were properly handled during the refinement.
In this article, the temporal progression of quality indicators in the Cambridge Structural Database is evaluated statistically as a simplistic and accessible measure for structural quality trends. R 1 showed a strong decrease until 1980 followed by comparatively small changes, whereas wR 2 increased significantly between 2000 and 2025. Residual electron-density extrema remained broadly stable, although the magnitude of the residual densities showed a small significant decrease. Exploratory normalization by unit-cell volume produced decreasing recent R 1 and wR 2 ratios, whereas F (000)-normalized R 1 decreased and F (000)-normalized wR 2 remained stable. Also, quality indicators are plotted on an elemental basis, and their trends are described.
The ternary Zintl arsenide Eu 5 Ga 2 As 6 and two members of the Ba 5 In 2 As 6– x Sb x [ x = 0.49 (2) and 2.92 (2)] solid solution series were obtained from Pb-flux reactions and characterized by single-crystal X-ray diffraction methods. They adopt the uncommon Sr 5 Al 2 Sb 6 structure type and represent the first As-bearing compounds adopting this structure type. The polyanionic substructure consists of 1D chains of edge- and corner-sharing [ TrPn 4 ] ( Tr = Ga, In; Pn = As, Sb) tetrahedra extending along the [100] direction, with pendant [ Pn 2 ] dumbbells. Non-random As/Sb site preferences within the polyanionic substructure of Ba 5 In 2 As 6– x Sb x are also discussed. Formal electron counting supports valence-precise Zintl notation for all reported compositions. First-principles electronic structure calculations for Eu 5 Ga 2 As 6 reveal a moderate indirect band gap of ∼0.8 eV. Comparative calculations for the chemically related Eu 3 GaAs 3 phase, also isolated during the present study, predict a narrow direct band gap of ∼0.2 eV and provide additional context for the bonding and electronic structure of Eu 5 Ga 2 As 6 .
Three new complexes, namely, hydronium μ-hydroxido-μ-isobutyrato-bis[diaquaberyllium(II)] tris[triisobutyratodioxidouranium(VI)] dihydrate, (H3O)[Be2(C4H7O2)(OH)(H2O)4][U(C4H7O2)3O2]3·2H2O or (H3O)[Be2(μ-OH)(μ-i-but)(H2O)4][UO2(i-but)3]3·2H2O (I) [i-but denotes the isobutyrate ion CH3CH(CH3)COO-], poly[tri-μ4-isobutyrato-di-μ-oxido-rubidium(I)uranium(VI)], [RbU(C4H7O2)3O2]n or Rb[UO2(i-but)3] (II), and poly[pentaaquatetracosa-μ-crotonato-hexadeca-μ-oxido-tetrabarium(II)octauranium(VI)], [Ba4U8(C4H5O2)24O16(H2O)5]n or Ba4[UO2(crt)3]7[UO2(crt)3(H2O)](H2O)4 (III) (crt denotes the crotonate ion, C3H5COO-), were synthesized and their crystal structures were determined. In order to achieve general conclusions, a comparison of the new crystal structures with previously published structures was conducted. Complex I is the first compound containing a hydronium ion and Be atoms in an oxygen environment simultaneously. It was revealed that the new Rb isobutyratouranylate, II, features the same packing motif as in the butyrate-, crotonate- and methacrylate-containing analogues. Using the example of the Rb series of compounds, we evaluated the compliance of the sizes of the structural fragments based upon the change of their crystal system. It was shown that the packing motif of III strongly depends on the ratio of the reagents.
Cocrystal structures formed by trithiocyanuric acid (TTCA) and selected nitroimidazole derivatives, dimetridazole (DMZ·TTCA, C5H7N3O2·C3H3N3S3), tinidazole (TNZ·TTCA·MeOH, C8H13N3O4S·C3H3N3S3·CH3OH), ornidazole (ONZ·TTCA·MeOH, C7H10ClN3O3·C3H3N3S3·CH3OH, and ONZ·TTCA·H2O, C7H10ClN3O3·C3H3N3S3·H2O) and ronidazole (RNZ·TTCA and 2RNZ·2TTCA, both C6H8N4O4·C3H3N3S3) were investigated to identify recurring drug-coformer aggregation patterns and factors determining supramolecular architecture. Structural analysis showed that TTCA adopts two principal supramolecular motifs: the hydrogen-bonded R22(8) dimer and linear chain assemblies. Two dominant drug-coformer binding schemes were identified. The first involves N-H...N hydrogen bonding in the para position relative to the TTCA dimer, leading to four-molecule assemblies, which are accompanied by heteronuclear hydrogen bonding in the ortho position. The second motif is associated with TTCA linear chains, where drug molecules are linked through N-H...N interactions and further stabilized by direct intermolecular or solvent-mediated hydrogen bonding. The polymorphic structure 2RNZ·2TTCA combines both supramolecular strategies within a single-crystal architecture. Hirshfeld surface analysis and intermolecular energy calculations confirmed the importance of hydrogen-bond competition in determining the crystal packing and supramolecular organization in TTCA-based cocrystals.
Two Al-bearing mixed-metal oxides, Ba2.11(1)Pb0.89Al8.78(1)In2.22O20, (1), and BaAl1.57(2)Ga0.43O4, (2), were obtained serendipitously from Pb-flux reactions carried out in alumina crucibles. Single-crystal X-ray diffraction analysis determined that (1) crystallizes in the monoclinic space group C2/m [a = 15.9491 (11), b = 11.5929 (8), c = 5.1241 (3) Å and β = 108.644 (2)°] and can be viewed as a disordered derivative of the Pb3GeAl10O20 structure type. The structure contains mixed octahedrally coordinated Al/In sites and a split Ba/Pb position analogous to the Ba/Bi disorder in Ba2BiGa11O20. Compound (2) crystallizes in the hexagonal space group P63 [a = 9.0981 (3) and c = 8.7909 (4) Å], adopting a superstructure related to the BaAl2O4/SrAl2O4/BaZnGeO4 families of oxide materials. Its structure contains mixed Al/Ga tetrahedral sites and positional disorder of bridging O atoms. Electronic structure calculations based on ordered structural models indicate wide-bandgap semiconducting behavior, with a calculated bandgap of 3.63 eV for (1) and 3.80 eV for (2).
The crystal structure of the monoclinic α-[SeCl3][MoOCl4] polymorph, trichloridoselenium tetrachloridooxidomolybdate, is reported from a complete single-crystal X-ray diffraction study. Black-brown moisture-sensitive crystals were obtained from reactions of MoOCl4 and Se2Cl2 in sealed glass ampoules at 100 °C. The compound crystallizes in the space group P21/c and is isostructural with the tellurium analog, α-[TeCl3][MoOCl4]. Its structure consists of trigonal-pyramidal [SeCl3]+ cations and square-pyramidal [MoOCl4]- anions that dimerize through asymmetric Mo...Cl...Mo bridges to form centrosymmetric [Mo2O2Cl8]2- units. The SeIV centers exhibit characteristic 3 + 3 coordination, with three short primary Se-Cl bonds and three longer secondary Se...Cl contacts, yielding distorted [SeCl6] trigonal antiprisms. These contacts connect adjacent [Mo2O2Cl8]2- dimers into layers parallel to the bc plane. The electronic structure calculations show that α-[SeCl3][MoOCl4] has a band gap of ca 0.88 eV. Crystal orbital Hamilton population (COHP) and crystal orbital bond index (COBI) bonding analyses confirm that short primary contacts are covalent, whereas longer secondary Se...Cl and Mo...Cl contacts are significantly weaker yet structurally important for layered connectivity. The natural bond orbital (NBO) analysis further supports charge polarization between the [SeCl3]+ and [MoOCl4]- fragments, placing α-[SeCl3][MoOCl4] in the realm of layered ionic solids or even van der Waals materials. Bonding of the broad [ChCl3][MoOCl4] series (Ch = S, Se, Te) are discussed as well.
The tutorial on best practices in `0 K' DFT energy calculations on molecular crystal structures by van de Streek & Johnson [Acta Cryst. (2026), C82, 383-400] provides a highly accessible and practical guide for performing reliable periodic density functional theory calculations in organic crystals.
We report the first crystal structure of the telmisartan-tempol conjugate 2,2,6,6-tetramethyl-1-(λ'-oxidaneyl)piperidin-4-yl 4'-[(1,7'-dimethyl-2'-propyl-1H,3'H-[2,5'-bibenzo[d]imidazol]-3'-yl)methyl]-[1,1'-biphenyl]-2-carboxylate free radical (YK-4-250, C42H46N5O3), a dual-function inhibitor designed to target both the angiotensin II type 1 receptor (AT1R) and reactive oxygen species (ROS). Structural analysis reveals a unique crystal architecture in which the nitroxide radical is stabilized within a sterically protected environment while preserving the telmisartan pharmacophore essential for high-affinity receptor antagonism. YK-4-250 is a novel small-molecule conjugate of telmisartan and tempol that incorporates a catalytic stabilized nitroxide radical and was rationally designed to mitigate gastrointestinal acute radiation syndrome (GI-ARS).
The crystal structure of the known low-temperature anhydrous phase of psilocybin {3-[2-(dimethylamino)ethyl]-1 H -indol-4-yl dihydrogen phosphate, C 12 H 17 N 2 O 4 P} is reported. While the structure was previously characterized using powder X-ray diffraction, this study describes the first determination via single-crystal X-ray diffraction. High-resolution structural models were obtained both before and after in situ dehydration, allowing for a direct comparison of the lattice response to water loss.
Homoleptic lead(II) complexes with the monodentate O-donor ligand antipyrine (anti or 1,5-dimethyl-2-phenyl-2,3-dihydro-1H-pyrazol-3-one) were synthesized in the form of triflate (trifluoromethanesulfonate) and perchlorate salts, namely, hexakis(1,5-dimethyl-2-phenyl-2,3-dihydro-1H-pyrazol-3-one-κO)lead(II) bis(trifluoromethanesulfonate), [Pb(C11H12N2O)6](CF3SO3)2, and hexakis(1,5-dimethyl-2-phenyl-2,3-dihydro-1H-pyrazol-3-one-κO)lead(II) bis(perchlorate), [Pb(C11H12N2O)6](ClO4)2, abbreviated as [Pb(anti)6]X2 (X = OTf and ClO4). In the case of [Pb(anti)6](OTf)2, two polymorphic forms crystallizing in the monoclinic I2/a (1a) and triclinic P\overline 1 (1b) space groups were distinguished. [Pb(anti)6](ClO4)2 (2) crystallized in the trigonal space group P\overline 3. The crystal structures were determined by single-crystal X-ray diffraction. In all three structures, the metal ion is surrounded by six O atoms from the antipyrine molecules. Compounds 1a and 2 display regular and holodirected octahedral geometry with three similar [2.496 (1), 2.523 (1) and 2.539 (1) Å] or six equivalent Pb-O bond lengths [2.474 (2) Å]. Complex 1b has lower hemidirected symmetry, forming a ψ-pentagonal bipyramid, with six different Pb-O bond distances in the range 2.327 (2)-2.852 (2) Å and one position occupied by a lone electron pair. Shorter C-H...O contacts in 1b [2.998 (4) and 3.141 (4) Å] compared to those in 1a [3.354 (2) and 3.365 (2) Å] and 2 [3.360 (3) and 3.384 (3) Å] between the antipyrine molecules and the counter-ions seem to stabilize the active lone pair. In all three structures, the [Pb(anti)6]2+ cations organize into a hexagonal columnar packing, while the ordered counter-ions occupy the free cavities between them. Density functional theory (DFT) calculations reveal that the isolated [Pb(anti)6]2+ cation favours a distorted hemidirected geometry. The calculated eccentricity values [0.14 (1b) and 0 (1a and 2)] confirm the active and inert behaviour of the 6s2 lone pair, respectively. The distribution of the Pb-O bond lengths for the homoleptic lead(II) complexes with a PbO6 core was presented. Correlations between Pb-O bond lengths and cordination number (CN) for the selected lead(II) and lead(IV) complexes were analysed.
The title novel phosphonium-based manganese(II) hybrid crystal, {(C24H26O2P)2[MnCl4]}n or (TBTP)2[MnCl4], was synthesized via slow evaporation. Single-crystal X-ray diffraction reveals that it crystallizes in the monoclinic space group P21/n, featuring discrete slightly distorted tetrahedral [MnCl4]2- anions and bulky (TBTP)+ cations [(TBTP)+ is (tert-butoxycarbonyl)methyltriphenylphosphonium] with weak C-H...Cl interactions. The material exhibits green luminescence centred at 515 nm with a millisecond-scale lifetime (2.83 ms), which is unequivocally assigned to the long-lived spin-forbidden Mn2+ 4T1→6A1 d-d transition. Electronic structure calculations reveal a direct band gap (with the noted underestimation typical of the PBE functional) and, more importantly, a clear spatial separation of the frontier orbitals between the inorganic and organic components. This orbital separation, likely aiding in the isolation of the luminescent [MnCl4]2- centres, is consistent with the observed long emission lifetime. This work enriches the family of phosphonium-based hybrid metal halides and provides insights into the structure-property relationships governing Mn2+ emission in such systems.
Three new hydrous molecular salts, namely, 2,4,6-triaminopyrimidin-1-ium anthranilate (2-aminobenzoate) monohydrate, C4H8N5+·C7H6NO2-·H2O (I), 2,4,6-triaminopyrimidin-1-ium 5-aminoisophthalate monohydrate, C4H8N5+·C8H6NO4-·H2O (II), and bis(2,4,6-triaminopyrimidin-1-ium) 4-aminophthalate trihydrate, 2C4H8N5+·C8H5NO42-·3H2O (III), have been synthesized and characterized by single-crystal X-ray diffraction techniques. In all three crystal structures, protonation of the pyrimidine moiety occurs at the N1 position and is reflected in a widening of the C-N-C bond angle. In all three cases, protonation of the triaminopyrimidine (TAP) molecule leads to the formation of the robust charge-assisted R22(8) TAP-carboxylate heterosynthon, which acts as the primary supramolecular building unit. In salt I, TAP base pairing and water-mediated contacts produce tetrameric aggregates and a DDDA (D is donor and A is acceptor) supramolecular array that propagates into a 3D hydrogen-bonded sheet structure. Salt II exhibits a combination of R22(8), R32(8) and R24(8) motifs that fuse to form a continuous hydrogen-bonded chain characterized by a DDDAAA supramolecular array. These chains further assemble into extended sheets which are interconnected by higher-order ring motifs and are reinforced by π-π stacking interactions between the pyrimidine ring and the aromatic anion. The structure of salt III displays the most complex architecture. Multiple hydrogen-bonded arrays, including DADA-type quadruple motifs and large fused-ring motifs, arise through co-operative N-H...O, N-H...N and O-H...O interactions involving the cations, anion and water molecules, resulting in a densely interconnected 3D framework. Hirshfeld surface analysis reveals that H...H contacts dominate the crystal packing, while O...H/H...O and N...H/H...N interactions play a crucial role in directing the supramolecular assembly. The study highlights how anion topology and hydration influence hydrogen-bond hierarchy and supramolecular dimensionality in TAP-based salts.
The crystal structure of silver hypodiphosphate, Ag 4 (P 2 O 6 ), was determined using 3D ED. The average structure is hexagonal, described in the space group P 6 3 / mcm , and is isomorphous with the average structure of known Li 4 (P 2 S 6 ). The silver cations form hexagonal atomic ring layers and the hypodiphosphate anions occupy channels that centre every hexagonal ring, with the P—P bond oriented along the unique c axis. The hypodiphosphate P 2 O 6 4− anions are disordered, with the P atoms occupying two positions having 50% occupancy each and with O atoms common for both positions of the anion. The O atoms form an octahedral coordination environment for the silver cations. The hypodiphosphate anions are stacked into columns along the unique axis direction. Neighbouring hypodiphosphate columns may have P—P bonds on the same (ferro-type) or on different (antiferro-type) levels. This correlated disorder manifests itself in diffuse scattering observed on hkl layers with uneven l values. Simulations based on an Ising-type model with geometric frustration align well with the experimental data, providing insight into the short-range antiferro-like arrangement of disordered hypodiphosphate anions.
A new member of the recently developed family of porous metal halide semiconductors (PMHS) is reported. Crystals of bis(4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo[8.8.8]hexacosane) tetradecachloridopentaplumbate(II), {(C18H38N2O6)2[Pb5Cl14]}n or (DHS)2Pb5Cl14 (DHS is the double-protonated [2.2.2]cryptand) were obtained via solution chemistry protocols, with concentrated HCl as the reaction solvent. Single-crystal X-ray diffraction (XRD) revealed a two-dimensional inorganic framework, crystallizing in the hexagonal space group P63/m with Z' = 1/6, separated and charge-balanced by double-protonated DHS organic cations. The corresponding material is isostructural with the previously reported water-stable (DHS)2Pb5Br14 and both feature broad light emission at room temperature. The lead chloride layer is disordered and was modeled as two components with partial occupancies of 0.585 and 0.415. (DHS)2Pb5Cl14 decomposes when placed in water, giving rise to PbCl2 as a degradation product. We attribute the sharp difference in water stability between the bromide and chloride analogs to differences in hydration energy and halide ionic radius, which affect their affinity for water molecules through hydrogen bonding.
