Octahedral Core Research Articles

Temperature-dependent luminescent copper nanoclusters with noncovalent interactions for determination of β-galactosidase activity.

The synthesis of anovel bidentate ligand-protected copper nanocluster via a solid-state strategyis reported. Single-crystal X-ray diffraction analysis result reveals that the copper nanocluster features an octahedral core (Cu6) coordinated by six ligands. Noncovalent interactions (C-H…π and π…π) exist between the copper nanoclusters. The copper nanocluster displays luminescence even at 250°C. The luminescence intensity is linearly correlated with temperature changes. The copper nanocluster can assemble into luminescent nanosheets whose emission is quenched by 4-nitrophenol. Spectroscopic analysis and theoretical calculations results demonstrate that the inner filter effect and electron transfer cause the above quenching effect. A probe based on luminescent nanosheets was constructed for β-galactosidase activity determination. The linearity range is 3.3-91.8 U·L-1, and the limit of detection is 0.45 U·L-1. This probe was also evaluated for determination of theβ-galactosidase activity in human serum via spiking experiments. The recoveries ranged from 96.2% to 101.8%.

Introduction of Niobium in the Chemistry of Octahedral Chalcogenide Clusters: Synthesis and Detailed Study of Compounds Based on Condensed and Discrete {Re5NbQ8} (Q = S or Se) Cores.

It is known that niobium practically does not form cluster chalcogenide compounds of the {M6(μ3-Q8)} type, which are widespread in the chemistry of group 6 and 7 metals. This work reports the preparation of a series of polymeric and discrete niobium-containing heterometallic clusters based on the {Re5Nb(μ3-S8)} and {Re5Nb(μ3-Se8)} cores. The compounds were prepared by the high-temperature reaction between rhenium and niobium dichalcogenides in a KCN melt. The 1D polymers K5[Re5NbQ8(CN)5] (Q = S or Se), which were formed as a result of the reaction, crystallize in the structural type of K6[Mo6Se8(CN)5], similar to the previously reported heterometallic clusters K6[Re6-xMoxQ8(CN)5] (x = 2-3). The polymers were solubilized to form discrete anionic clusters [Re5NbQ8(CN)6]4-. The structure and properties of the new clusters were investigated using a combination of X-ray diffraction analysis, UV/vis spectroscopy, high-resolution electrospray mass spectrometry, cyclic voltammetry, and DFT calculations. Among other features, the compounds showed high electrochemical activity, being able to form three redox states in solution with reversible transitions. It was found that redox potentials of the isoelectronic octahedral clusters demonstrate a strong cathodic shift in the sequence [Re5OsSe8(CN)6]3- > [Re6Se8(CN)6]4- > [Re5MoSe8(CN)6]5- > [Re5NbSe8(CN)6]6-, illustrating the effect of systematic changes in the composition of octahedral cluster cores on their properties.

Fluorescent probe for Fe3+ detection based on a guest molecular luminescent metal–organic framework

The zinc(II) bis-(8-hydroxyquinoline) (Znq2) has excellent photoluminescence properties, and its fluorescence emission can be significantly quenched by Fe3+ in water. To accelerate the detection response of Znq2 to Fe3+, a luminescent metal–organic framework Znq2@ZIF-8 based on guest molecular luminescence was constructed by growing zeolite imidazolate framework-8 (ZIF-8) on the outer surface of Znq2. The results show that the prepared Znq2@ZIF-8 has an octahedral core–shell structure, a particle size of approximately 1–3 μm, an enhanced specific surface area of 1105.41 m2 g−1, and with a stable green luminescence at 495 nm. A fluorescence analytical method was developed for the detection of Fe3+ in water, the correlation coefficients were significant in the Fe3+ concentration range of 0–600 μmol L−1, and the limit of detection was as low as 3.89 μmol L−1. The spiked recoveries of tap water samples demonstrated that the method could be applied to practical applications. The mechanism of fluorescence detection is that Fe3+ participates in the competitive coordination of Znq2@ZIF-8 metal centers, leading to the collapse of the crystal structure, meanwhile, Fe3+ produces a certain degree of competitive absorption of the excitation light of Znq2@ZIF-8. This method was applied for the detection of Fe3+ in water with good selectivity, anti-interference ability, and has the potential to be used as a rapid detection method.

Homoleptic ruthenium(II) complexes bearing imidazol(in)ium-2-dithiocarboxylate ligands: synthesis, characterization, and redox properties.

Five cationic ruthenium(II) chelates with the generic formula [Ru(S2C·NHC)3](PF6)2 were readily obtained upon cleavage of the [RuCl2(p-cymene)]2 dimer with representative imidazol(in)ium-2-dithiocarboxylate zwitterions (NHC·CS2) in the presence of KPF6. The homoleptic complexes were fully characterized by various analytical techniques and the molecular structure of one of them was determined by single-crystal X-ray diffraction analysis. As expected, it featured an octahedral RuS6 core surrounded by three imidazol(in)ium rings and their nitrogen substituents. The robustness of the Ru-S bonds combined with the chelate effect of the κ2-S,S'-dithiocarboxylate units and the steric protection imparted by bulky 1,3-diarylimidazol(in)ium groups most likely accounted for the outstanding stability of these species in solution. Cyclic voltammetry showed that the five homoleptic complexes featured characteristic waves for a monoelectronic redox process corresponding to the RuIII/RuII couple with E1/2 values ranging between 0.97 and 1.27 V vs. Ag/AgCl. This half-wave potential was clearly dependent on the nature of their ancillary ligands as the evolution of the Ep,ox values roughly paralleled the basicity sequence of the NHCs used to prepare them, in line with the trends observed when monitoring the chemical shifts of the CS2- unit on 13C NMR spectroscopy and the CS2- asymmetric stretching vibration wavenumbers on IR spectroscopy.

Improved rate capability and long cycle life of metal-organic framework derived TiO2@V2O5 composite as an efficient cathode for sodium-ion batteries

Vanadium oxide on carbon nanoporous structure (V2O5/C) as a potential cathode material for sodium-ion batteries (SIBs) offers significant specific capacities in energy storage systems but suffers from slow ionic diffusivity upon long cycling at higher current rates, thereby generally resulting in substandard electrochemical performance. This study suggests a facile strategy to enhance the electrochemical performance of V2O5/C as a cathode in sodium-ion batteries via titanium (Ti) doping using the pre-synthesized Ti-doped vanadium-based metal-organic framework template (V-MIL-101) as the precursor, which can be converted into a sophisticated core-shell type structure in which titania nanoparticle-based shell surrounds the vanadium oxide with a porous carbon-based octahedral core. Structural characterization reveals that Ti-doping forms a protective layer around vanadium based MIL-101 octahedrons that, upon pyrolysis, preserves the octahedral geometry and transforms into a nanoporous core-shell structure. It also greatly enhances the electrochemical performance as a cathode for SIBs. The titania-doped vanadium oxide structures represent higher specific capacities than the undoped vanadium oxide cathode, whereas among all the titania-doped samples, the 3 wt% TiO2@V2O5/C exhibited a much higher reversible capacity of 276.2 mAh/g as compared to the other cathode samples at 0.1C current rate and was able to retain a capacity of 250.1 mAh/g with a high coulombic efficiency after 200 cycles. Titanium species induce the formation of oxygen vacancies and V+5 species, which enhance the electrode's electric conductivity and ion diffusion—the stable octahedrons with a porous structure and carbon hybridisation in 3 wt% TiO2@V2O5/C could facilitate ion/electron transfer through shortened diffusion pathways.

Hydrogen Storage Mechanism by Gas-Phase Vanadium Cluster Cations Revealed by Thermal Desorption Spectrometry.

The adsorption of hydrogen on gas-phase vanadium cluster cations, Vn+ (n = 3-14), at 300 K and desorption of hydrogen from hydride clusters, VnHm+, upon heating were observed experimentally by combined thermal desorption spectrometry and mass spectrometry analyses. The ratio m/n was approximately 1.3 for all n values at 300 K, which was reduced to approximately zero at 1000 K. For n = 4, stable cluster geometries of V4Hm+ (m = 0, 2, 4, and 6) were investigated by DFT calculations, revealing that V4 adopted a trigonal pyramidal structure and the H atoms adsorbed mainly on the μ2 bridge sites. The adsorption reaction pathway of one H2 molecule on V4+ was also investigated. The experimentally estimated desorption energies of the H2 molecules were consistent with their calculated binding energies. Among the observed hydride clusters, V6H8+ was found to be significantly thermally durable, probably because of its close-packed octahedral V6 core structure, with H atoms occupying all hollow sites.

Systematic Study of Vibrational Spectra of Octahedral Rhenium Clusters {Re6S8-xBrx}Bry (x = 0, 1, 2, 3, 4) with Mixed Sulfur/Bromine Inner Ligands

A series of rhenium compounds with the octahedral cluster core {Re6S8-xBrx} (x = 0–4): with molecular and polymeric structure were obtained. In these compounds the cluster core composition varies monotonically, the geometry of the cluster and the rhenium coordination polyhedron are retained unchanged, while the symmetry of the cluster changes. The vibrational spectra (Raman and IR) were recorded and analyzed for compounds with all possible S/Br ratios in the cluster core. The group vibrations of clusters were attributed with the use of DFT calculations of vibrational spectra. It is shown that the set of main characteristic bands is retained in both ionic and polymeric compounds regardless of the composition and the symmetry of the cluster core while the observed vibration frequencies of these bands depend on the S/Br ratio in the cluster core. In particular, the group Re–S stretching vibrations (A1g(S8) and T2g(S8) modes) shifted to higher frequencies with the increase in the number of Br atoms in the cluster. The difference in the connectivity in polymeric compounds leads to an increase in the number of bands in the spectra and to the disappearance of the A1g(Br) modes.

Molecular Dynamics Simulation Study on Self-Assembly of Polymer-Grafted Nanocrystals: From Isotropic Cores to Anisotropic Cores.

The self-assembly of polymer-grafted nanocrystals (PGNCs) is an important method to manufacture novel nanomaterials. Herein, we focus on the self-assembly of three types of PGNCs with differently shaped cores including sphere, octahedron, and cube by molecular dynamics simulation. By characterizing the positional and orientational order of the assembled superlattices, we construct the phase diagrams as a function of the grafting density and polymer chain length. For PGNCs with spherical cores, we observe the transition from the FCC phase to the BCC phase due to the packing entropy of the ligand polymer chains. For PGNCs with anisotropic cores, the close-packed FCC phase is replaced by the C-BCC phase (octahedral cores) or the C-triclinic phase (cubic cores) due to the directional entropy of core shape. We also study the assembly dynamics by tracking the time evolution of the positional and orientational order. We elucidate the relationship of grafting density and polymer chain length to the packing entropy and directional entropy and reveal their important effects on assembled structures. In general, our simulation results provide useful guidelines for the programmable assembly of PGNCs.

Fabrication and Growth Mechanism of Nano-Octahedrons: A Study on Cu2O Core-Shell Structures for Oxygen Evolution Reaction

This paper explores the process and growth mechanism involved in fabricating nano-octahedrons. Using two key components, CTAB and hydrazine hydrate, leads to the formation of octahedral shapes. A Cu2O octahedral core–shell structure was successfully created by employing a coating technique, and its performance in the oxygen evolution reaction (OER) was thoroughly evaluated. Due to its high dispersibility in ammonia solution, Cu2O serves as an excellent representative for other components. Additionally, this chapter provides a detailed account of the production of octahedral nanocages through the ammonia etching method. Notably, the Cu2O nano octahedra demonstrate superior OER performance compared to commercial RuO2, exhibiting a significantly low overpotential of only 370 mV at 10 mA cm−2. These findings bear important implications for designing stable core/shell nanostructures and hollow structures by implementing appropriate chemicals while also deepening our understanding of the formation of octahedral shapes.

Magnesium(I) Reduction of Aluminum(III) Hydride Complexes: Generation of Mixed Valence Aluminum (AlI/Al0) Hydride Cluster Compounds, [Al6H8(NR3)2{Mg(β-diketiminate)}4

Reduction of a range of amido- and aryloxy-aluminum dihydride complexes, e.g. [AlH2(NR3){N(SiMe3)2}] (NR3 = NMe3 or N-methylpiperidine (NMP)), with β-diketiminato dimagnesium(I) reagents, [{(ArNacnac)Mg}2] (ArNacnac = [HC(MeCNAr)2]-, Ar = mesityl (Mes) or 2,6-xylyl (Xyl)), have afforded deep red mixed valence aluminum hydride cluster compounds, [Al6H8(NR3)2{Mg(ArNacnac)}4], which have an average Al oxidation state of +0.66, the lowest for any well-defined aluminum hydride compound. In the solid-state, the clusters are shown to have distorted octahedral Al6 cores, having zero-valent Al axial sites and mono-valent AlH2- equatorial units. Several novel by-products were isolated from the reactions that gave the clusters, including the Mg-Al bonded magnesio-aluminate complexes, [(ArNacnac)(Me3N)Mg-Al(μ-H)3[{Mg(ArNacnac)}2(μ-H)]]. Computational analyses of one aluminum hydride cluster revealed its Al6 core to be electronically delocalized, and to possess one unoccupied, and six occupied, skeletal molecular orbitals.

Magnesium(I) Reduction of Aluminum(III) Hydride Complexes: Generation of Mixed Valence Aluminum (AlI/Al0) Hydride Cluster Compounds, [Al6H8(NR3)2{Mg(β‐diketiminate)}4]**

AbstractReduction of a range of amido‐ and aryloxy‐aluminum dihydride complexes, e.g. [AlH2(NR3){N(SiMe3)2}] (NR3=NMe3 or N‐methylpiperidine (NMP)), with β‐diketiminato dimagnesium(I) reagents, [{(ArNacnac)Mg}2] (ArNacnac=[HC(MeCNAr)2]−, Ar=mesityl (Mes) or 2,6‐xylyl (Xyl)), have afforded deep red mixed valence aluminum hydride cluster compounds, [Al6H8(NR3)2{Mg(ArNacnac)}4], which have an average Al oxidation state of +0.66, the lowest for any well‐defined aluminum hydride compound. In the solid‐state, the clusters are shown to have distorted octahedral Al6 cores, having zero‐valent Al axial sites and mono‐valent AlH2− equatorial units. Several novel by‐products were isolated from the reactions that gave the clusters, including the Mg−Al bonded magnesio‐aluminate complexes, [(ArNacnac)(Me3N)Mg−Al(μ‐H)3[{Mg(ArNacnac)}2(μ‐H)]]. Computational analyses of one aluminum hydride cluster revealed its Al6 core to be electronically delocalized, and to possess one unoccupied, and six occupied, skeletal molecular orbitals.

Tetra-kis(tri-ethyl-enediamin-1-ium) dodeca-μ2-chlorido-hexakis(thio-cyanato-κN)hexa-octa-hedro-niobate.

The crystal structure of the cluster complex salt, (C6H13N2)4[Nb6(NCS)6Cl12] or (H-DABCO)4[Nb6Cl12(NCS)6] (DABCO = tri-ethyl-enedi-amine or 1,4-di-aza-bicyclo-[2.2.2]octa-ne), comprises octa-hedral Nb6 cluster cores, which are μ2-coordinated by 12 chloride ligands (bridging the octa-hedral edges, inner ligand sphere). Furthermore, each Nb atom is N-bonded to a terminal thio-cyanate ligand (outer ligand sphere). The discrete clusters carry a charge of -4, which is compensated by four monoprotonated DABCO mol-ecules. These are arranged in rows, which are N-H⋯Cl and N-H⋯N hydrogen bonded to the anions and among each other.

Directing Energy Flow in Core-Shell Nanostructures for Efficient Plasmon-Enhanced Electrocatalysis.

Conjugating plasmonic metals with catalytically active materials with controlled configurations can harness their light energy harvesting ability in catalysis. Herein, we present a well-defined core-shell nanostructure composed of an octahedral Au nanocrystal core and a PdPt alloy shell as a bifunctional energy conversion platform for plasmon-enhanced electrocatalysis. The prepared Au@PdPt core-shell nanostructures exhibited significant enhancements in electrocatalytic activity for methanol oxidation and oxygen reduction reactions under visible-light irradiation. Our experimental and computational studies revealed that the electronic hybridization of Pd and Pt allows the alloy material to have a large imaginary dielectric function, which can efficiently induce the shell-biased distribution of plasmon energy upon illumination and, hence, its relaxation at the catalytically active region to promote electrocatalysis.

Polypyridyl-based Co(III) complexes of vitamin B6 Schiff base for photoactivated antibacterial therapy.

Herein, five novel polypyridyl-based Co(III) complexes of Schiff bases, viz., [Co(dpa)(L1)]Cl (1), [Co(dpa)(L2)]Cl (2), [Co(L3)(L2)]Cl (3), [Co(L3)(L1)]Cl (4), and [Co(L4)(L1)]Cl (5), where dpa (dipicolylamine) = bis(2-pyridylmethyl)amine; H2L1 = (E)-2-((2-hydroxybenzylidene)amino)phenol; H2L2 = (E)-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylpyridin-3-ol; L3 = 4'-phenyl-2,2':6',2''-terpyridine (ph-tpy); and L4 = 4'-ferrocenyl-2,2':6',2''-terpyridine (Fc-tpy), were synthesized and characterized. Complexes 1, 3, and 4 were structurally characterized by single-crystal XRD, indicating an octahedral CoIIIN4O2 coordination core. The absorption bands of these complexes were observed in the visible range with a λmax at ∼430-485 nm. Complex 5 displayed an extra absorption band near 545 nm because of a ferrocene moiety. These absorptions in the visible region reflect the potential of the complexes to act as visible-light antimicrobial photodynamic therapy (aPDT) agents. All of these complexes showed reactive oxygen species (ROS)-mediated antibacterial effects against S. aureus (Gram-positive) and E. coli (Gram-negative bacteria) upon low-energy visible light (0.5 J cm-2, 400-700 nm) exposure. Additionally, 1-5 did not show any toxicity toward A549 (Human Lung adenocarcinoma) cells, reflecting their selective bacteria-killing abilities.

Structure, optical properties, and catalytic applications of alkynyl-protected M4Rh2 (M = Ag/Au) nanoclusters with atomic precision: a comparative study.

We report two atomically precise alloy nanoclusters of Ag4Rh2(CCArF)8(PPh3)2 and Au4Rh2(CCArF)8(PPh3)2 (Ar = 3,5-(CF3)2C6H3, abbreviated as Ag4Rh2 and Au4Rh2, respectively) co-protected by alkynyl and phosphine ligands. Both clusters have identical octahedral metal core configurations and can be termed superatoms with two free electrons. However, they possess different optical features, manifested by totally different absorbance peaks, and drastically different emission peaks, and also, Ag4Rh2 has a much higher fluorescence quantum yield (18.43%) than Au4Rh2 (4.98%). Moreover, Au4Rh2 exhibited markedly superior catalytic performance in the electrochemical hydrogen evolution reaction (HER), manifested by a much lower overpotential at 10 mA cm-2 and better stability. Density functional theory (DFT) calculations revealed that the free energy change of Au4Rh2 for the adsorption of two H* (0.64 eV) is lower than that of Ag4Rh2 for the adsorption of one H* (-0.90 eV) after stripping a single alkynyl ligand from the cluster. In contrast, Ag4Rh2 demonstrated much stronger catalytic capability for catalyzing 4-nitrophenol reduction. The present study provides an exquisite example to understand the structure-property relationship of atomically precise alloy nanoclusters, and emphasizes the importance of fine-tuning of the physicochemical properties and catalytic performance of the metal nanoclusters through modulating the metal core and beyond.

Front Cover: Hexanuclear Niobium Cluster Alcoholates – First Representatives with Isopropanolato Ligands (Z. Anorg. Allg. Chem. 20/2022)

The cover picture shows the nucleophilic attack of alkoxides on the hexanuclear cluster compound, which carries halide (iodido and chloride) ligands, [Nb6Cl12I6]2−. Li(OC3H7) is used as strongly basic agent in solution-based chemical reactions near room temperature. The first representatives of cluster compounds with isopropanolato ligands on the inner coordination sites of the octahedral metal atom cores are formed.(DOI: 10.1002/zaac.202200241).

Hexanuclear Niobium Cluster Alcoholates – First Representatives with Isopropanolato Ligands

AbstractFour new compounds were synthesized which belong to the so far very small group of hexanuclear niobium cluster alcoholates. These are [Mg(HOCH3)6]3[Nb6Cl12(OCH3)6]2 ⋅ 6CH3OH (1), (Ph4P)2[Nb6(OC2H5)12Cl6] (2), (Ph4P)2[Nb6(OC3H7)i4Cli8Cla6] (3) and (NC5H6)2[Nb6(OC3H7)12Cl6] (4). The last two compounds represent the first examples with isopropanolato ligands on the inner coordination sites of the octahedral metal atom cores. The X‐ray structures of 1–3 have been determined. All cluster units with alcoholato ligands on the inner sites carry 14 cluster‐based electrons (CBEs), as do all other so far known cluster alcoholates. The cluster unit in Compound 1, which carries chloride ligands on the inner coordination sites, is a 15 CBE unit. The cluster anion in 3 has four inner ligand sites occupied by isopropanolate anions, which are arranged trans to each other and define a common plane. Because of the smaller size of the alcoholato O donor atom compared to halogenido ligands matrix effects are not much or not at all present in the cluster anions of 2 and 3 (and 4) and thereby the Nb−Nb distances are much smaller than found in cluster units with halogenido ligands.

The A B C's of metasomatism in the North Atlantic Craton during Pangea breakup; characterized by fluid inclusions in Chidliak diamonds

Here we report the nitrogen characteristics and composition of high-density fluid (HDF) trapped in microinclusions in a suite of fibrous diamonds from the ~142 Ma Chidliak CH-7 kimberlite pipe, the Hall Peninsula, southern Baffin Island, Nunavut. Within these diamonds, we observe three populations based on the chemistry of the encapsulated HDFs, the diamond's nitrogen aggregation states, and the diamond color. ‘Chidliak C' diamonds contain highly silicic HDFs, have nitrogen in A- and C-centers (with 5–20% in C-centers), and a characteristic intense yellow color. ‘Chidliak A' diamonds contain silicic to low-Mg carbonatitic HDFs, carry nitrogen solely in A-centers, and are mostly colorless. A third population, ‘Chidliak B', has grey color and distinctive low-K2O silicic to low-Mg carbonatitic HDF compositions and overall smoother and less fractionated trace element pattern relative to ‘Chidliak C' and ‘Chidliak A' diamonds; they carry nitrogen in A- and B-centers (with ~15% in B-centers) and are characterized by a grey hue. An eclogitic paragenesis of all diamonds is evident by the HDF compositional variation as well as the presence of omphacitic clinopyroxene inclusions. The appearance of a diamond with A- and B-centers in its octahedral core and A- and C-centers in its coat suggests formation at two distinct events at a similar depth. Combined with pressure and mantle residence estimates based on nitrogen aggregation considerations, we argue that the three diamond populations formed at the relatively shallow region of the lithosphere (likely <180 km) during distinct metasomatic events in the North Atlantic Craton (NAC) since the Proterozoic. The youngest event by silicic HDFs took place close in time to kimberlite activity at 142–157 Ma, as evident by the preservation of nitrogen C-centers in ‘Chidliak C' diamonds. A link between this event and the mid-lithosphere discontinuity (MLD) in eclogitic portions of the cratonic lithosphere in Chidliak is plausible. The timing of ‘Chidliak A' diamonds formation by more carbonatitic HDFs is less well constrained, but can be related to Ca-rich metasomatism observed in local peridotite xenoliths and/or alkaline magmatism between 610 and 550 Ma. A possible link between the formation of ‘Chidliak B' diamonds and the timing of Mesoproterozoic olivine lamproite magmatism ca. 1400 Ma is suggested based on the HDF trace element composition and the aggregated nature of nitrogen in these diamonds. The nitrogen systematics and eclogitic source of the fibrous diamonds are comparable with those observed for previously studied gem-quality diamonds from Chidliak. We suggest that these similarities show a temporal connection and mutual crystallization of the two diamond types. This strengthens the involvement of HDFs in the formation of gem-quality diamonds.

Low-Frequency Oscillations in Optical Measurements of Metal-Nanoparticle Vibrations.

Time-resolved optical measurements of vibrating metal nanoparticles have been used extensively to probe the ultrafast mechanical properties of the nanoparticles and of the surrounding liquid, but nearly all investigations so far have been limited to the linear regime. Here, we report the observation of a low-frequency oscillating signal in transient-absorption measurements of nanoparticles with octahedral gold cores and cubic silver shells; the signal appears at the difference of two mechanical vibrational frequencies in the particles, suggesting a nonlinear mixing process. We tentatively attribute this proposed mixing to a nonlinear coupling between a vibrational mode of the nanoparticle and its optical-frequency plasmon resonance. The optimization of this nonlinear transduction may enable high-efficiency opto-mechanical frequency mixing in the GHz-THz frequency regime.

Cluster Compounds with Oxidised, Hexanuclear [Nb6 Cli 12 Ia 6 ]n- Anions (n=2 or 3).

Four mixed‐halide cluster salts with chloride‐iodide‐supported octahedral Nb6 metal atoms cores were prepared and investigated. The cluster anions have the formula [Nb6Cli 12Ia 6] n− with Cl occupying the inner ligand sites and I the outer one. They are one‐ or two‐electron‐oxidized (n=2 or 3) with respect to the starting material cluster. (Ph4P)+ and (PPN)+ function as counter cations. The X‐ray structures reveal a mixed occupation of the outer sites for only one compound, (PPN)3[Nb6Cli 12Ia 5.047(9)Cla 0.953]. All four compounds are obtained in high yield. If in the chemical reactions a mixture of acetic anhydride, CH2Cl2, and trimethylsilyl iodide is used, the resulting acidic conditions lead to form the two‐electron‐oxidised species (n=2) with 14 cluster‐based electrons (CBEs). If only acetic anhydride is used, the 15 CBE species (n=3) is obtained in high yield. Interesting intermolecular bonding is found in (Ph4P)2[Nb6Cli 12Ia 6] ⋅ 4CH2Cl2 with I⋅⋅⋅I halogen bonding and π‐π bonding interactions between the phenyl rings of the cations in (PPN)3[Nb6Cli 12Ia 5.047(9)Cla 0.953]. The solubility of (Ph4P)2[Nb6Cli 12Ia 6] ⋅ 4CH2Cl2 has been determined qualitatively in a variety of solvents, and good solubility in the aprotic solvents CH3CN, THF and CH2Cl2 has been found.