Stefanie Dehnen

We report a new concept to lower the melting temperature (T _m ) of inorganic‐organic hybrid adamantane‐based cluster compounds by forming unprecedented eutectic cluster mixtures with organic adamantane derivatives. Blending of clusters of the type [( p ‐MeC ₆ H ₄ Si(CH ₂ SnPhE) ₃ ] (E = S, Se, Te) with (3‐F‐4‐Me‐C ₆ H ₃ ) ₃ Ad, (3‐F‐4‐Me‐Ph) ₄ Ad, and (4‐MeO‐C ₆ H ₄ ) ₄ Ad was achieved by mechanical mixing and led to decreased T _m while retaining the components’ chemical identity. Such adamantane‐type compounds are known to exhibit strongly non‐linear optical properties: upon irradiation with a continuous wave (CW) laser diode, they respond either by second‐harmonic generation (SHG), if being crystalline, or by white‐light generation (WLG) with corresponding broadband emission, if being intrinsically amorphous or transformed into a glassy state. Herein, we show that this feature is preserved in the eutectic mixtures, hence, we can report superior properties of these cluster‐based materials that combine favorable nonlinear optical behavior with lowered T _m , which facilitates their processing for future use.

Despite the significant advancements in noble metal-based nanocluster research, challenges remain in making specific metal kernel geometries, especially protected by bulky ligand shells. Here, we synthesized and structurally characterized a neutral silver cluster, [Ag14(TRZ)12(TPP)3], where TRZ and TPP refer to 6-(dibutylamino)–1,3,5-triazine-2,4-dithiolate and triphenylphosphine, respectively. The cluster was synthesized under ambient conditions using a TPP-assisted, solvent-mediated structural transformation from the [Ag31(TRZ)10]2– precursor cluster. This non-face-centered cubic (non-fcc) cluster features a central Ag5 trigonal bipyramidal core surrounded by a distinct Ag(6+3) tricapped trigonal prismatic (TTP) shell. This type of unconventional metal skeleton differs significantly from the well-known fcc-type Ag14 cluster, which typically has an octahedral Ag6 core and a cubic Ag8 shell. It is also the first metal cluster to be structurally resolved with TRZ ligands. Quantum chemical calculations indicate that although the non-fcc Ag14 skeleton has a lower cohesive energy than the fcc Ag14 analogues, bulky TRZ ligands featuring multiple sulfide linkages and n-butyl chains stabilize it. The as-synthesized Ag14 cluster is non-emissive, but exposure to oxygen converts it into an orange-emitting species. Density functional theory calculations indicate that the TTP Ag(6+3) shell prefers binding with oxygen. Emissive lifetime and femtosecond transient absorption showed that oxygenation provided greater stabilization of excited states than the parent Ag14 cluster. This study presents a new approach for designing metal clusters with unique structural frameworks with unconventional ligand environments and allows for harvesting surface-sensitive electronic properties.

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Chalcogenido metalates have long been regarded as cluster-based semiconductors, yet their conductive nature has not been studied in detail, although such compounds do bear potential for use in electronics. Herein, we introduce four new compounds, (HDMMP)2[Sn3Se7]·(HDMMP)2[Sn2Se6]0.5 (1), (C3C1Im)3(HDMMP)[Sn3Se7]2 (2), and their Cs+-exchanged derivatives, 1Cs and 2Cs (HDMMP = protonated 2,6-dimethylmorpholine; C3C1Im = 1-propyl-3-methyl-imidazolium), all of which are based on 2D-{[Sn3Se7]2–} anionic substructures. Detailed current–voltage measurements on single crystals of 1 and 2 as well as their ion-exchanged derivatives were undertaken that indicated complex nonlinear and highly structure-dependent conductive properties. For 1, the studies demonstrate that intercalation of molecular 0D-[Sn2Se6]4– units with higher negative charge density as compared to the 2D-{[Sn3Se7]2–} networks creates open circuits that lead to nonconductive characteristics. In contrast, the I–V measurements carried out on 2 suggest a combination of electrical and ionic conductivity along horizontal and vertical directions of this compound based exclusively on the 2D-{[Sn3Se7]2–} substructures. Cation exchange in 1 and 2 with Cs+, which in the case of compound 1 is accompanied by an extraction of the molecular anions 0D-[Sn2Se6]4–, confirms this suggestion: a set of I–V characteristics, including I–V hysteresis and chronoamperometry traces, demonstrate that both compounds are now conductive, with ionic conductivity dominating along both vertical and horizontal directions of 1Cs and 2Cs. Notably, compound 1 not only turned into a conductive material 1Cs, it additionally became slightly more conductive this way than 2Cs. In summary, this work unravels the nonlinear conductive nature of selenido stannates and represents a step forward toward functional materials based on chalcogenido metalates.

The access of metal chalcogenide clusters with tunable properties remains challenging. For a given geometric cluster structure, chemical and physical properties are defined by the exact composition. With a binary metal chalcogenide cluster core, one can reach a certain degree of tunability, but an even finer definition is possible by expanding the concept to ternary cluster composition. As a case example, we address adamantane-type organotin chalcogenide clusters of the general composition [(RSn)4E6] (R = organic group, E = Se, Te) and herein report the targeted access of corresponding species exhibiting ternary clusters with two different types of chalcogen atoms involved, [(RSn)4E6–xE′x]. We report three different methods for the synthetic access of E/E′ mixtures, including chalcogen exchange between preformed homochalcogenide clusters [(RSn)4E6] and[(RSn)4E′6] in solution. Extensive 119Sn NMR studies on corresponding reaction mixtures with different ratios of the starting materials, in combination with sophisticated quantum chemical calculations of the chemical shifts, unambiguously confirm that all statistically possible clusters form in solution. Isolation of selected species in single-crystalline form also indicates the existence of ternary cluster cores with a narrow dispersion of species around the given E:E′ ratios. Our results represent an important step toward fine-tuning of metal chalcogenide cluster-based materials.

The realization of solid‐state batteries (SSBs) hinges upon the development of solid electrolytes (SEs) exhibiting superior functional properties. Halide SEs are promising candidates due to their high room‐temperature ionic conductivity and favorable (chemo)mechanical properties. However, their electrochemical stability and degradation processes under operating conditions remain largely unexplored. Herein, we present lithium niobium halide SEs, LiX‐NbCl ₅ (X = F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ ), with emphasis placed on LiNbCl ₆ and LiNbCl ₅ Br. Structural analysis unveils the materials to be predominantly amorphous, interspersed with nanocrystalline domains, with both LiNbCl ₆ and LiNbCl ₅ Br exhibiting ionic conductivities above 3.5 mS cm ⁻¹ at 25°C. Mechanical properties and pressure‐dependent ionic conductivities were also examined, revealing good densification behavior and low activation volumes. When used as catholyte in SSBs with layered oxide cathodes, the cells show high initial Coulomb efficiencies (>90%) and deliver specific discharge capacities of over 200 mAh g ⁻¹ . Using differential electrochemical mass spectrometry, we demonstrate that chlorine evolves at the end of charge, which can be mitigated to some extent by introducing bromine, leading to enhanced cyclability. Overall, our study indicates that halide substitution has a positive effect on electrochemical stability without impairing ionic conductivity, and that gas evolution must be considered in halide‐based SEs.

Sodium‐ion solid electrolytes with high ionic conductivity at low mechanical pressures are essential for the practical implementation of solid‐state batteries. We investigated the combined influence of pressure and temperature on the conductivity of the sulfide‐based sodium electrolyte Na _2.9 Sb _0.9 W _0.1 S ₄ . A series of thermo‐mechanical protocols were applied in which the pellets were first subject to high‐pressure compaction (≤ 664 MPa) and subsequently annealed at 250°C for 1 h under a constant pressure (97 MPa). Electrochemical impedance spectroscopy (EIS) was performed to monitor the ionic conductivity. The most effective protocol (664 MPa → 250°C, 97 MPa) yielded a record superionic conductivity of 44.7 mS cm ⁻¹ at pressures ≥ 18 MPa. After one week under constant pressure (97 MPa), and subsequent relaxation to 1.3 MPa, the conductivity remained at 13.1 mS cm ⁻¹ . Lower‐pressure treatment also caused high conductivity (9.1 mS cm ⁻¹ at 1.3 MPa), demonstrating the material's robustness. Powder X‐ray diffraction confirmed a pressure‐induced transition from tetragonal to cubic modifications of Na _2.9 Sb _0.9 W _0.1 S ₄ , correlating with the conductivity enhancement. The results demonstrate that systematic pressure and temperature treatments afford super‐high sodium‐ion conductivity in Na _2.9 Sb _0.9 W _0.1 S ₄ at pressures compatible with industrial battery manufacturing, highlighting its promise as a solid electrolyte for next‐generation sodium‐ion batteries.

Delocalized [4 n + 2]π-aromaticity in cyclic planar unsaturated organic molecules conceptually underpins organic chemistry. Recently, the study of all-metal aromaticity has burgeoned, but although there has been interest in cyclo-{E ₃ } (E = P, As, Sb, Bi) species as cyclopropenium analogues, the formation of cyclo-{Bi ₃ } remains rare. Thus, the potential aromaticity of 2/6π-cyclo-Bi ₃ ^+/3− , as the heaviest 6 p analogue of cyclopropylium, has remained open to different interpretations. Here we report the formation of diuranium and dithorium 6π-cyclo-Bi ₃ ³⁻ inverse sandwich complexes, complementing the small number of acyclic- and cyclic-Bi _n ( n = 3–5) compounds. The 6π-cyclo-Bi ₃ ³⁻ ring exhibits substantial ring currents, similar to 6π-benzene, 2π-(C ₃ H ₃ ) ⁺ or 6π-(C ₃ H ₃ ) ³⁻ . Calculations reveal similar ring currents for 6π-cyclo-Bi ₃ ³⁻ , 2π-cyclo-Bi ₃ ⁺ and 0π-cyclo-Bi ₃ ³⁺ , demonstrating σ-aromaticity that is dominant over π-aromaticity in cyclo-Bi ₃ ³⁻ , despite the favourability of describing cyclo-Bi ₃ ³⁻ with localized rather than delocalized bond descriptions. Confirmation of 6π-cyclo-Bi ₃ ³⁻ σ-aromaticity provides the heaviest all-metal 6 p analogue to π-aromatic (C ₃ H ₃ ) ^+/3− , leading to organic–inorganic aromaticity benchmarking.