Single-crystal X-ray Diffraction Research Articles

Self-assembly of supramolecular double helix from a tetrapeptide and direct visualization by Scanning Tunneling Microscopy.

This work reports single-crystal X-ray diffraction (XRD), Scanning Tunneling Microscopy (STM), and quantum mechanics calculations of the 310-helical peptide Z-(Aib)2-L-Dap(Boc)-Aib-NHiPr (Aib, α-aminoisobutyric acid; Dap, 2,3-diaminopropionic acid; Z, benzyloxycarbonyl; Boc, t-butoxycarbonyl). The peptide forms a double-helical superstructure, studied by XRD and STM. Such architecture is rare in short peptides. Here, we show, by combining XRD, STM that this intriguing conformational feature is not driven by crystal packing; rather, it is an intrinsic property of this peptide. Indeed, the double helix is clearly detected also by STM, where crystal packing cannot be invoked. XRD reveals that intermolecular H-bonds stabilize two left-handed supra-helices (tertiary structure) that develop around a 6-fold screw axis. Then, two supra-helices are intertwined in a quaternary structure as a left-handed, double supra-helix, where C-H⋯π interactions play a crucial role. STM images show the formation of long, isolated "necklaces" (> 110 nm). They are of left and right helical handedness. Their size agrees with the XRD finding. DFT calculations allowed us to weigh the contribution of the different intermolecular interactions in the two single supra-helices and the supramolecular double-helix. Interestingly, we were able to conclude that the contribution of the C-H⋯π interactions to the binding energies is close to 50%.

Combination of phenylsilsesquioxane and acetate ligands as an approach to a record high nuclear Cu13Na2-cage. Synthesis, unique structure, and catalytic activity.

Self-assembly synthesis of mixed-ligand (silsesquioxane/acetate) complex allows to isolate record high nuclear copper(II) Cu13-cage (1). In the presence of two additional sodium ions, a unique molecular architecture, with triple combination of ligands (cyclic and acyclic silsesquioxanes as well as acetates), has been formed. The structure was established by single-crystal X-ray diffraction based on the use of synchrotron radiation. Complex 1 was evaluated as precatalyst in the Baeyer-Villiger oxidation of cyclohexanone towards ε-caprolactone, employing hydrogen peroxide, tert-butyl hydroperoxide (TBHP) or m-chloroperoxybenzoic acid (mCPBA) as oxidants, in an aqueous acidic acetonitrile medium. The direct formation of the lactone from cyclohexane via a tandem peroxidative oxidation/Baeyer-Villiger oxidation was also studied. For both substrates, the best results (ε-caprolactone yields up to 100% or 26%, from cyclohexanone or cyclohexane, respectively) were achieved with mCPBA under considerably mild conditions, i.e., conventional heating at 50 °C for 4 h or microwave (MW) irradiation at 80 °C for only 30 minutes.

Abstract A003: In vitro anticancer activities of some organoplatinum (IV) derivatives

Abstract Recent investigations into organoplatinum (IV) complexes as potential anticancer agents have shown considerable promise. Unlike cisplatin, these compounds are more stable in physiological environments and generally exhibit fewer side effects. Additionally, chelating aromatic ancillary ligands have been found to enhance the intercalation of metal-based agents into tumor DNA. This study aimed to synthesize novel organoplatinum (IV) complexes with chelating aromatic ligands and evaluate their anticancer efficacy through in vitro assays. Five complexes were synthesized: [Pt(CH3)2X2{2,2’-bipyridine-4,4’-R2}] (X = Br, I; R = H, CO2H) and [{Pt(CH3)3}2(μ-I)2(μ-adenine)]. These were characterized by single crystal X-ray diffraction and assessed for anticancer activity. The MTT assays indicated that the [Pt(CH3)2X2{2,2’-bipyridine}] complexes were more cytotoxic to the ZR-75-1 human breast cancer cell line than cisplatin, with LC50 values of 6.1 µM for X = I, 11.5 µM for X = Br, compared to 16.4 µM for cisplatin. Furthermore, the sulforhodamine B assays conducted by the National Cancer Institute's Developmental Therapeutics Program revealed that [Pt(CH3)3}2(μ-I)2(μ-adenine)] was highly effective against various cancer cell lines. Notably, it showed an LC50 value of 5.20 µM against the glioblastoma multiforme SF-539 cell line, whereas cisplatin and temozolomide had LC50 values exceeding 100 µM. Similarly, [Pt(CH3)3}2(μ-I)2(μ-adenine)] had an LC50 value of 5.99 µM against the renal carcinoma RXF-393 cell line, with cisplatin and cabozantinib showing LC50 values above 100 µM. While these results highlight the superior cytotoxicity of the tested organoplatinum (IV) complexes, further research and development are required before these compounds can be considered for commercial use as chemotherapy drugs. Citation Format: William A. Howard. In vitro anticancer activities of some organoplatinum (IV) derivatives [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Optimizing Therapeutic Efficacy and Tolerability through Cancer Chemistry; 2024 Dec 9-11; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(12_Suppl):Abstract nr A003

Gradient Luminescence Enhancement in Organic Metal Halide Perovskites via the Suppression of [SbCln]3-n Unit Distortion.

Intrinsic stereochemical activity of the 5s2 electron configuration in Sb3+ leads to structural distortion within [SbCln]3-n units, which, while stabilizing the material, paradoxically diminishes luminescence intensity due to induced asymmetry. To address this issue, a strategy, which encompasses increasing the structural dimensions and introducing In3+ doping, was developed to mitigate the geometrical distortion in the [SbCln]3-n units within the metal-organic perovskite (DABCO)2Sb2Cl10·H2O and (DABCO)2SbCdCl9·2H2O (DABCO = triethylenediamine). This dimensional augmentation confines lattice distortion effectively, and the In3+ doping modifies the 5s2 electron configuration of Sb3+, thereby reducing the distortion at its origin. The unique suitability of indium-based halides as a matrix for Sb3+ doping is underscored by our approach, which capitalizes on their ability to regulate the electron configuration of Sb3+. This strategy has been validated through crystallographic data from single-crystal X-ray diffraction. By effectively reducing the adverse effects of geometric distortion, several hundred-fold enhancements in the luminescent intensity of the material have been achieved by our methodology, leading to potential applications in white-light LEDs. This advancement not only highlights the pivotal role of structural symmetry in the optical properties of materials but also exemplifies the power of material engineering to optimize the optical performance.

The crystal structures of methyl prop-2-ynoate, dimethyl fumarate and their protonated species.

Methyl prop-2-ynoate (C4H4O2) was investigated in the binary superacidic system HF/MF5 (M = Sb or As) and dimethyl fumarate (C6H8O4) in the superacidic system HF/SbF5, as well as HF/BF3. The starting materials methyl prop-2-ynoate and dimethyl fumarate were crystallized, the former for the first time. The protonated species of these esters, namely, (1-methoxyprop-2-yn-1-ylidene)oxidanium hexafluoroarsenate, C4H5O2+ AsF6-, 1,4-dimethoxy-4-oxobut-2-en-1-ylidene]oxidanium tetrafluoroborate bis(hydrogen fluoride), C6H9O4+ BF4- 2HF, and hemi{[1,4-dimethoxy-4-oxidaniumylidenebut-2-en-1-ylidene]oxidanium} undecafluorodiantimonate, 0.5C6H10O42+ Sb2F11-, were characterized by single-crystal X-ray diffraction and Raman spectroscopy. The protonated species were recrystallized from anhydrous hydrogen fluoride. In the solid state of the monoprotonated species of methyl prop-2-ynoate and the diprotonated species of dimethyl fumarate, strong intramolecular O-H...F hydrogen bonds build a three-dimensional network. The monoprotonated species of dimethyl fumarate builds chains by strong O-H...O hydrogen bonds between the cations.

Chemical Synthesis of ~1 nm Multilevel Capacitor-like Particles with Atomic Precision.

Can the chemically synthesized nanoparticles act as nanodevices or nanomachines? Herein, we demonstrated this feasibility. A novel nanocluster (ultrasmall nanoparticle) [Au44Cd20(m-MBT)40][N(C8H17)4]2 (Au44Cd20 in short, m-MBTH: m-methylbenzenethiol) obtained via developing a synthesis method has a cannula-like structure of the outer shell and an internal sleeve, revealed by single-crystal X-ray diffraction. Natural population analysis (NPA) charge calculations, charge carrier transport of Au44Cd20 (during which an intra-nanocluster anti-galvanic reaction was observed) after unneutral charging using NaBH4 as well as voltammetry proved the capacitor-like character of Au44Cd20. The subsidiary capacitor-like character of the outer shell of Au44Cd20 was further probed via NPA charge calculations and electrocatalytic reduction of CO2 to CO. Thus, this study predicts a new era of engineering metal nanoparticles for realizing atomically precise ultrasmall nanodevices and nanomachines.

Cadmium(II)-Organic Frameworks with the Polynuclear Unit: Dimensionality Control and Luminescence Response to Pyridine

New porous metal-organic frameworks (MOF) [Cd7(Btdc)7(Bpa)2(Dmf)2(H2O)2] · 15Dmf · 2H2O (I) and [Cd7(Btdc)7(Bpe)2(Dmf)2] · 15Dmf · 3H2O (II) (H2Btdc is 2,2’-bithiophene-5,5’-dicarboxylic acid, Bpa is 1,2-bis(4-pyridyl)ethane, Bpe is 1,2-bis(4-pyridyl)ethylene, and Dmf is N,N-dimethylformamide) are synthesized under solvatothermal conditions. The structures and compositions of the compounds are determined by single-crystal X-ray diffraction (XRD) (CIF files ССDС nos. 2364290 (I) and 2364289 (II)) and confirmed by powder XRD, elemental analysis, thermogravimetry, and IR spectroscopy. Compound I has a 2D structure based on the heptanuclear discrete building unit {Cd7} with the linear structure. Compound II is a 3D MOF in which the {Cd7} building units are linked into a continuous chain motif due to additional interactions. The formation of discrete or continuous chains is directly related to the nature of the N-donor bridging ligand (Bpe or Bpa). Compounds I and II have open structures with the accessible volume about 50%. The solvate molecules are replaced by thiophene, benzene, and pyridine, and the luminescence properties of the prepared adducts are studied. Luminescence quenching in the presence of thiophene and an increase in the luminescence intensity in the presence of pyridine accompanied by a change in the quantum yield by 4–5 times are shown.

Neutral Terbium(III) Tris(complex) with 4,4,5,5,6,6,6-Heptafluoro-1-(1-methyl-1H-pyrazol-4-yl)hexane-1,3-dione: Synthesis, Structure, and Spectral Luminescence Properties

The reaction of 1,3-diketone containing 1-methyl-1H-pyrazol-4-yl and perfluoropropyl fragments with TbCl3·6H2O in the presence of NaOH in ethanol is studied. The molecular and crystal structures of the complex are studied by single-crystal X-ray diffraction (XRD). Compound [Tb(L)3(EtOH)2] crystallizes in the triclinic crystal system with the space group. The geometry of the coordination polyhedron {LnO8} corresponds to a square antiprism. Intermolecular interactions N…H–O, C–H…O, and C–H…F leading to the formation of supramolecular chains are observed in crystals of the complex. The UV-irradiated complex exhibits green luminescence caused by transitions 5D4 → 7Fj (j = 2–6) characteristic of the Tb3+ ion. The main photophysical luminescence parameters are determined, and the scheme of energy transfer in the complex is proposed. The synthesized compound can be of interest as an independent luminophore or as the initial substance for the synthesis of heteroligand complexes by the substitution of ethanol molecules in the internal coordination sphere.

Crystal Structures of Sulfobetaine-8 Solvates: Bend Hydrophobic Chains and Doubly Charge-Assisted Hydrogen Bonds N+CH⋯−O3S

Three novel solvatomorphs (C13H29NO3S•CH3OH, 1; C13H29NO3S•0.113(H2O), 2; C13H29NO3S•0.038(H2O), 3) of zwitterionic sulfobetaine-8 were obtained and their structures were determined using single-crystal X-Ray diffraction. In all cases dimethyl–amino substituted hydrophobic chains -(CH2)3-N+Me2-(CH2)7-Me exhibit kinks at nitrogen atoms resulted from strong intra- and intermolecular CH⋯O hydrogen bonds between negatively charged sulfonic anion -O3S- and positively charged tetraalkylammonium fragments. Periodic (solid state) DFT calculations for structure 1 showed that the energy of the intermolecular hydrogen bonds CH…O is very high, at about 17 kJ/mol. In hydrates 2 and 3, water molecules play the structure-forming role since they interconnect hydrophobic layers by HOH…-O3S hydrogen bonds. The location of only partially occupied water molecules in the interlayer space leads to low stability of both crystals 2 and 3 in open air.

Fluoride Clusterfullerenes: Tuning Metal-Metal Bonding and Magnetic Properties via Single Fluorine Atom Doping.

Endohedral fullerenes are known for their exceptional ability to host metal clusters that contain unique bonding motifs. In this study, we report a facile strategy to synthesize a new family of clusterfullerenes, fluoride clusterfullerenes (FCFs). This work demonstrates that actinides and rare earth metals as well as alkaline earth metals can be encapsulated within a variety of fullerene cages, and these fullerenes can be obtained in their pristine form without additional functionalization methods. Notably, Th2F@Ih(7)-C80 and CaScF@Cs(6)-C82 were isolated and their molecular structures and magnetic properties were characterized by X-ray single-crystal diffraction and multiple spectroscopic techniques as well as DFT calculations. These findings reveal that the unique internal addition of a single fluorine atom significantly alters the metal-metal bonding interactions of Th-Th and Ca-Sc. While Th2@Ih(7)-C80 hosts a σ2 Th-Th bond, an unprecedented actinide-actinide (Th-Th) single electron metal-metal bond is formed inside Th2F@Ih(7)-C80 upon the internal addition of fluoride. Similarly, while a Ca-Sc single electron bond exists in CaSc@Cs(6)-C82, which exhibits excellent molecular qubit properties, the addition of fluoride transforms the compound into a singlet. The present study not only highlights the successful synthesis of a novel family of FCFs, which will likely be an extensive family, it also shows that fluorine doping can induce novel metal-metal bonding motifs leading to potentially intriguing magnetic properties.

Supramolecular Gels Derived from Primary Ammonium salts of Naproxen and its Amino Acid Derivatives: Design, Synthesis, Structures and its Application as Anti-cancer Agent Against Melanoma Cell B16-F10.

Supramolecular synthon approach was employed to develop a self-drug-delivery system based on organic salt based supramolecular gelators. One such key gelator NAP-PHE∙PEA derived from naproxen-phenylalanine conjugate and phenethylamine showed ability to gel both water and organic solvents. Supramolecular interactions such as π-π and C-H…π were probed by variable-temperature 1H-NMR spectroscopy in the hydrogelation process of NAP-PHE∙PEA. Single crystal structures of nine out of twelve salts were determined and the supramolecular synthon present therein was carefully analyzed. Intriguing insights of the gel-network structure was also investigated by structure-property correlation based on single-crystal and powder X-ray diffraction analysis of gelator/nongelator salts. The gelator salt NAP-PHE∙PEA displayed significant anti-cancer property against cancer cells (B16-F10. HeLa and A375); it was found non-cytotoxic against normal cell lines (E.derm and HEK-293) at comparable concentrations as revealed by MTT assays. The gelator salt NAP-PHE∙PEA also displayed significant anti-cancer behaviour against B16-F10 (scratch assay) and HeLa (multi-cellular tumour spheroid). The methyl salicylate gel of NAP-PHE∙PEA displayed shape-sustaining, load-bearing, self-healing properties along with rheoreversibility, which are considered important for topical applications.

In-Depth Structural Analysis of a Stapled Pentapeptide and Its Assembly Into Straight α-Helices.

Peptide self-assembly is a complex hierarchical process involving the progressive formation of secondary structures, such as α-helices, β-sheets, and turns, during the early stages. It is precisely these multi-component building blocks that contribute to the complexity of protein assemblies in living organisms. While coiled coils are well-understood in protein folding, determining the structural characteristics governing their lateral packing remains challenging. Here, a stapled pentapeptide (CIHs) that forms straight α-helices are reported. Using single crystal X-ray diffraction and Microcrystal electron diffraction (Micro-ED), the atomic-level assembly mechanism of CIHs is investigated. This study describes the specific geometric standards based on these α-helical building blocks and their interactions. By modulating the hydrophobic interface between these blocks via side-chain alterations, this study validates that these mutant assemblies can inherit the specific spatial geometry and regular interaction interfaces of straight α-helices. These results provide a simple template for exploring the hierarchical assembly of straight α-helices and studying the impact of side chains on lateral packing, opening new avenues for the development of high-order peptide assemblies based on straight α-helices.

Synthesis, Optical, and Magnetic Properties of the Mixed Chalcogenide Semiconductor Series Eu(II)2SiSexS4-x, Prepared via the Flux-Assisted Boron Chalcogen Mixture Method.

We report a detailed structural study of a series of five new quaternary Eu(II)-containing mixed chalcogenide phases, Eu2SiSe0.85S3.15, Eu2SiSe2.4S1.6, Eu2SiSe2.6S1.4, Eu2SiSe3.1S0.9, and Eu2SiSe4, synthesized using the flux-assisted boron chalcogen mixture (BCM) method. High-quality crystals were grown, and their crystal structures were determined by single-crystal X-ray diffraction. All members of the Eu2SiSexS4-x series crystallize in the monoclinic crystal system with space group P21/m, except Eu2SiSe4, which crystallizes in the P21 space group. The crystal structure of Eu2SiSexS4-x exhibits a complex three-dimensional network and is primarily composed of distorted trigonal prismatic EuQ6 polyhedra that are interconnected by SiQ4 tetrahedra. Polycrystalline powders were used for physical property measurements, including the magnetic susceptibility and UV-vis diffuse reflectance. Magnetic measurements indicated paramagnetic behavior with a slightly negative Weiss constant (θ = -13.54). The band gaps of the materials were determined from diffuse reflectance data, with optical band gaps estimated to be 2.04(2) eV, 1.98(2) eV, and 1.90(2) eV for Eu2SiSe0.85S3.15, Eu2SiSe2.6S1.4, and Eu2SiSe4, respectively. Band gap tuning was achieved by partially or fully replacing the S sites with Se.

Employing the Trifluoromethyl Group on a 5/5 Fused Triazolo[4,3-b][1,2,4]triazole Backbone: A Viable Strategy for Attaining Balanced Energetics.

In this study, we synthesized trifluoromethyl-substituted bis-triazole nitrogen-rich compounds (3-5) using a simple, cost-effective method. The newly made compounds were characterized using NMR, IR, elemental analysis, TGA-DSC, and single-crystal X-ray diffraction (for compounds 3 and 4). They demonstrated high density (1.82-1.92 g cm-3), moderate detonation performance (7567-7905 m s-1), good thermal stability (146-215 °C), and low sensitivity to impact (40 J) and friction (360 N), offering high potential nature as a cationic component in energetic salts, defense, and civilian applications.

An Adaptive Metal-Organic Framework Discriminates Xylene Isomers by Shape-Responsive Deformation.

The separation of xylene isomers, especially para-xylene, is a crucial but challenging process in the chemical industry due to their similar molecular dimensions. Here, a flexible metal-organic framework, Ni(ina)2, (ina = isonicotinic acid) is employed to effectively discriminate xylene isomers. The adsorbent with adaptive deformation accommodates the shapes of isomer molecules, thereby translating their subtle shape differences into characteristic framework deformation energies. Through a combination of multiple local flexibility behaviors, Ni(ina)2 exhibits guest-specific structural transformations that energetically favor para-xylene over other isomers. Single-crystal X-ray diffraction, in situ powder X-ray diffraction, and theoretical investigations validate this "adaptive fitting" mechanism, where the degree of structural deformation scales with the mismatch between the molecular shape and pore geometry. As a result, Ni(ina)2 achieves exceptional para-xylene selectivity in both liquid and vapor phase separations, maintaining a high para-xylene purity and productivity. This work demonstrates a novel strategy of exploiting framework flexibility to address challenging molecular separations and provides fresh insights into the design of selective adsorbents.

Atomistic Origins of Conductance Switching in an ε-Cu0.9V2O5 Neuromorphic Single Crystal Oscillator.

Building artificial neurons and synapses is key to achieving the promise of energy efficiency and acceleration envisioned for brain-inspired information processing. Emulating the spiking behavior of biological neurons in physical materials requires precise programming of conductance nonlinearities. Strong correlated solid-state compounds exhibit pronounced nonlinearities such as metal-insulator transitions arising from dynamic electron-electron and electron-lattice interactions. However, a detailed understanding of atomic rearrangements and their implications for electronic structure remains obscure. In this work, we unveil discontinuous conductance switching from an antiferromagnetic insulator to a paramagnetic metal in ε-Cu0.9V2O5. Distinctively, fashioning nonlinear dynamical oscillators from entire millimeter-sized crystals allows us to map the structural transformations underpinning conductance switching at an atomistic scale using single-crystal X-ray diffraction. We observe superlattice ordering of Cu ions between [V4O10] layers at low temperatures, a direct result of interchain Cu-ion migration and intrachain reorganization. The resulting charge and spin ordering along the vanadium oxide framework stabilizes an insulating state. Using X-ray absorption and emission spectroscopies, assigned with the aid of electronic structure calculations and measurements of partially and completely decuprated samples, we find that Cu 3d and V 3d orbitals are closely overlapped near the Fermi level. The filling and overlap of these states, specifically the narrowing/broadening of V 3dxy states near the Fermi level, mediate conductance switching upon Cu-ion rearrangement. Understanding the mechanisms of conductance nonlinearities in terms of ion motion along specific trajectories can enable the atomistic design of neuromorphic active elements through strategies such as cointercalation and site-selective modification.

A new terpestacin-type sesterterpenoid with tricyclic 3/15/5 scaffold from an endophytic fungus Neofusicoccum sp. J019

ABSTACT Chemical investigation of an endophytic fungus, Neofusicoccum sp. J019, isolated from the plant species Cynanchum chinense R. Br., has led to the identification of an undescribed terpestacin-type sesterterpenoid, neofusistacin (1), together with two analogues (2 and 3). The structure of 1 was elucidated by extensive spectroscopic analyses including UV, IR, 1D, and 2D NMR, HRESIMS, and its absolute configuration was unambiguously confirmed by a single crystal X-ray diffraction analysis. Compound 1 is featured by a rare 3/15/5-fused tricyclic scaffold in terpestacin-type sesterterpenoid. The anti-inflammatory activities of compounds 1–3 were evaluated in vitro, but none of them showed obvious anti-inflammatory activities at the concentration of 100 μM. No antibacterial activity against Escherichia coli ATCC 25922, Salmonella enterica subsp. enterica ATCC 14028, and Staphylococcus aureus subsp. aureus ATCC 29213 was found for compounds 1–3 at the concentration of 100 μM.

Design, synthesis, X-ray crystal structure, and antifungal evaluation of new acetohydrazide derivatives containing a 4-thioquinazoline moiety.

To find efficient agricultural fungicides, 29 new 4-thioquinazoline-containing acetohydrazide derivatives were prepared and tested for their fungicidal properties. All of the target compounds were characterized by 1H and 13C nuclear magnetic resonance and high-resolution mass spectrometry techniques, and the molecular structure of compound A2 was verified by single-crystal X-ray diffraction measurement. The experimental results revealed that many compounds from this series had impressive inhibition efficacies in vitro against the tested fungi. For example, compound A25 was identified as the best fungicidal agent against Rhizoctonia solani with an EC50 (half-maximal effective concentration) value of 0.66 μg mL-1, superior to those of the commercial fungicides chlorothalonil, carbendazim and boscalid. Additionally, this compound displayed favorable protection and curative activities in vivo against rice sheath blight caused by R. solani. Antifungal mechanistic studies on compound A25 indicated that this compound exerted its strong anti-R. solani effects probably through an effective inhibition of fungal succinate dehydrogenase activity [half-maximal inhibitory concentration (IC50) = 4.88 μm] and the impairment of cell membrane integrity, based on the results from enzymatic bioassays, molecular docking studies, and scanning and transmission electron microscopy observations. Acetohydrazide derivatives containing the 4-thioquinazoline moiety had the potential to be employed as lead compounds for developing more efficient agricultural fungicides in the near future. © 2024 Society of Chemical Industry.

Heavy Atom Cluster Chains with Strong Spin-Orbit Coupling and Magnetic Cations in Mn[PtBi6I12

In the search for new magnetic topological insulators with strong spin-orbit coupling, by following conceptual considerations that have already proven to be suitable, the bismuth-rich subiodide Mn[PtBi6I12] was discovered. Single crystals were grown from mixtures of the elements and BiI3 using a temperature program developed on the basis of thermal analyses. Single-crystal X-ray diffraction revealed a rhombohedral structure of the cuboctahedral cluster anions [PtBi6I12]2-, which are linked into chains via octahedrally coordinated Mn2+ cations. Partial substitution of Mn2+ by Bi3+ and vacancy formation are responsible for a phase width represented by the general formula (Mn1-3xBi2x)[PtBi6I12]. Density functional theory-based calculations and measurements of the electrical resistance showed that the compound is a semiconductor with a topologically trivial band gap. Nonstoichiometry of chain fragments, corresponding to n- and p-self-doping, strongly increases the conductivity, especially along the chains. The compound is paramagnetic at room temperature. Electron spin resonance spectra indicate an increase in spin correlations and the buildup of internal fields below 30 K.

Water Encapsulated [(Fe4Se4)Se4]6- Clusters in [Na6(H2O)18][Fe4Se8

[Na6(H2O)18][Fe4Se8] was synthesized using hydrothermal methods and characterized by single-crystal X-ray diffraction, 57Fe Mössbauer spectroscopy, magnetization, and muon spin resonance (μSR) measurements. The cubic crystal structure (space group I23, a = 11.785 Å, Z = 2) contains heterocubane-type clusters with Td symmetry. Four additional selenium atoms complete the tetrahedral coordination around the iron atoms, forming units. Notably, the selenide ligands do not interact with the sodium cations, as the Fe4Se86- cluster in [Na6(H2O)18][Fe4Se8] is exclusively surrounded by water molecules via weak Se···H-O hydrogen bonds. This is particularly remarkable given that [Fe4Q4] clusters are typically unstable in water. Quantum chemical calculations (DFT) confirm the crystal structure and improve the positions of the hydrogen atoms. 57Fe Mössbauer spectroscopy reveals that the spin ordering of the mixed-valence [Fe42.5+Se4]2+ cluster core mirrors the antiparallel spin arrangement found in analogous iron-sulfur clusters, such as , in protein-bound systems. An increase of the quadrupole splitting at low temperatures indicates changes of the orbital occupations. μSR Experiments show a reduction of the spin fluctuation frequency until the system becomes static at low temperatures, but no evidence of a S = 0 state above 2 K.