A Series of Cyclopentadienyl Lanthanum Complexes with Metalloid Germanium Clusters.

A series of cyclopentadienyllanthanum complexes with the disilylated metalloid germanium cluster [Ge9(Hyp)2]2- [Hyp = Si(SiMe3)3] has been prepared and fully characterized. The synthetic procedure is based on the salt metathesis reaction of two different cyclopentadienyllanthanum diiodides CpLaI2 (Cp: Cp*, pentamethylcyclopentadienyl; Cpttt, 1,2,4-tri-tert-butylcyclopentadienyl) with K2[Ge9(Hyp)2] in tetrahydrofuran (THF) with a subsequent extraction with n-hexane. The composition of the obtained compounds and the mode of coordination of the germanium cluster to the rare-earth metal are strongly influenced by the steric demand of the cyclopentadienyl ligands and the crystallization conditions. The centrosymmetric dimeric compounds with the common formula [CpLa(solv)(η2,3-Ge9(Hyp)2)]2 [1, Cp = Cp*, solv-THF; 2, Cp = Cpttt, solv-NCCH2C(Me)NSiMe3] have been isolated by the slow evaporation of a n-hexane solution, while a mononuclear complex [CptttLa(THF)2(η3-Ge9(Hyp)2)] (4) was found by crystallization from THF. The repeated recrystallization of 1 from n-hexane afforded the asymmetric dimer [Cp*La(THF)(η2,3-Ge9(Hyp)2)][Cp*La(η2,3-Ge9(Hyp)2)] (3) with only one coordinated THF molecule.

Tuning the electronic structure of gold cluster-assembled materials by altering organophosphine ligands.

Superatomic clusters can be assembled to build bulk matter, where the individual characteristics are preserved. The main benefit of these materials over conventional bulk species is the capability to tailor their features by altering the physicochemical identities of individual clusters. Electronic properties of metal clusters can be modified by a protective shell of ligands that attach to the surface and make the whole nanoparticle soluble in organic or aqueous solvents. In the present work, we demonstrate that properly chosen ligands provide not only steric protection from aggregation but also tune the redox activity of metal clusters. We investigate the role of the ligands in electronic structure tunability and ligand-field splitting. Our first-principles calculations agree with the experiments, showing that phosphine-protected gold materials are small gap semiconductors. The obtained bandgaps strongly depend on the ligand used. Hence, using phosphine and organophosphine ligands should be feasible and promising while designing the novel superatom-based materials since the desired range of the bandgap might be achieved (by the proper choice of the ligand).

Wearing face masks as a potential source for inhalation and oral uptake of inanimate toxins - A scoping review.

BACKGROUND: From 2020 to 2023 many people around the world were forced to wear masks for large proportions of the day based on mandates and laws. We aimed to study the potential of face masks for the content and release of inanimate toxins. METHODS: A scoping review of 1003 studies was performed (database search in PubMed/MEDLINE, qualitative and quantitative evaluation). RESULTS: 24 studies were included (experimental time 17 min to 15 days) evaluating content and/or release in 631 masks (273 surgical, 228 textile and 130 N95 masks). Most studies (63%) showed alarming results with high micro- and nanoplastics (MPs and NPs) release and exceedances could also be evidenced for volatile organic compounds (VOCs), xylene, acrolein, per-/polyfluoroalkyl substances (PFAS), phthalates (including di(2-ethylhexyl)-phthalate, DEHP) and for Pb, Cd, Co, Cu, Sb and TiO2. DISCUSSION: Of course, masks filter larger dirt and plastic particles and fibers from the air we breathe and have specific indications, but according to our data they also carry risks. Depending on the application, a risk-benefit analysis is necessary. CONCLUSION: Undoubtedly, mask mandates during the SARS-CoV-2 pandemic have been generating an additional source of potentially harmful exposition to toxins with health threatening and carcinogenic properties at population level with almost zero distance to the airways.

Synthesis and Investigation of a Soluble Distannene with no Trans-Bent Angle or Twisting in the Solid-State.

By treating KSiiPr3 with Sn[N(SiMe3)2]2 the distannene Sn2(TIPS)4 (TIPS=SiiPr3) is formed in a metathesis reaction. The crystal structure analysis of Sn2(TIPS)4 reveals a planar arrangement of the substituents in the solid-state and hence the second planar alkene like distannene of its kind. Due to the TIPS substituents, Sn2(TIPS)4 is well soluble in all commonly used organic solvents, opening the door for various analytics and reactivity studies. Due to its stability in solution, various reactions can be performed such as cycloaddition reactions with 2,3-dimethyl-1,3-butadiene (DMBD) and TMS-azide.

Direct laser induced writing of high precision gold nanosphere SERS patterns.

The high sensitivity and molecular fingerprint capability of Surface-Enhanced Raman Spectroscopy (SERS) have lead to a wide variety of applications ranging from classical physics, chemistry over biology to medicine. Equally, there are numerous methods to fabricate samples owing to the desired properties and to create the localized surface plasmon resonances (LSPRS). However, for many applications the LSPRs must be specifically localized on micrometer sized areas and multiple steps of lithography are needed to achieve the desired substrates. Here we present a fast and reliable direct laser induced writing (DIW) method to produce SERS substrates with active areas of interest in any desired size and shape in the micrometer regime. Afterwards, the SERS substrates have been functionalized with phthalocyanines. The DIW fabricated samples realize sub-monolayer sensitivity and an almost uniform enhancement over the entire area, which make this production method suitable for many sensing applications.

Synthesis and Reactivity of Fluorenyl-Based Germanium(II) Compounds.

We present the synthesis of alkyl-substituted germylenes GeFlu2, Ge(FluTMS)2, and FluTMSGeCl (Flu = 9H-fluorenyl, FluTMS = 9-trimethylsilyl-9H-fluorenyl) using bulky fluorenyl ring systems and modifications of that. GeFlu2 can only be crystallized as its three-membered ring trimer, whereby the reaction is accompanied by the formation of several byproducts, such as [Li(THF)4][Ge(Ge3Flu7H)]. These results led to the modification of the fluorenyl framework by substitution the one H atom in the 9-position by a TMS group. With the synthesis of the corresponding Li salt LiFluTMS, Ge(FluTMS)2 could be isolated in good yields in a further reaction. The homoleptic Ge(FluTMS)2 is found in its crystalline form as a monomer and thus belongs to the series of monomeric alkyl-substituted germylenes. Also, the corresponding monoalkyl-substituted halogenido germylene was isolated as a four-membered ring tetramer [FluTMSGeCl]4 during an unselective reaction. However, FluTMSGeCl undergoes significant stabilization through the formation of the monomeric phosphane adduct FluTMSGeCl·PEt3, which greatly increases the selectivity of the reaction. During further reactions of Ge(FluTMS)2 with a GeBr solution (toluol/nPr3P), more impressions of the reactivity of Ge(I)X solutions with germylenes were achieved, showing that those germylenes take part in the disproportionation reaction of metastable Ge(I) solutions to give oxidized Ge(IV) compounds like (FluTMS)2GeBr2.

Au30(PiPr2nBu)12Cl6-An Open Cluster Provides Insight into the Influence of the Sterical Demand of the Phosphine Ligand in the Formation of Metalloid Gold Clusters.

Phosphine-stabilized gold clusters are an important subgroup of metalloid gold cluster compounds and are important model compounds for nanoparticles. Although there are numerous gold clusters with different phosphine ligands, the effect of phosphine on cluster formation and structure remains unclear. While the linear alkyl-substituted phosphine gold chlorides result in a Au32 cluster, the bulky tBu3P leads to a Au20 cluster. The reduction of (iPr2nBuP)AuCl, with the steric demand of the phosphine ligand between the mentioned phosphines, results in the successful synthesis and crystallization of a new metalloid gold cluster, Au30(PiPr2nBu)12Cl6. Its structure is similar to the Au32 cluster but with two missing AuCl units. The UV/Vis studies and quantum chemical calculations show the similarities between the two clusters and the influence of the phosphine ligand in the synthesis of metalloid gold clusters.

Stabilization of Colloidal Germanium Nanoparticles: From the Study to the Prospects of the Application in Thin-Film Technology.

We present the stabilization of halide-terminated Ge nanoparticles prepared via a disproportionation reaction of metastable Ge(I)X solutions with well-defined size distribution. Further tailoring of the stability of the Ge nanoparticles was achieved using variations in the substituent. Ge nanoparticles obtained in this way are readily dispersed in organic solvents, long-term colloidally stable, and are perfect prerequisites for thin-film preparation. This gives these nanomaterials a future in surface-dependent optical applications, as shown for the halide-terminated nanoparticles.

Synthesis and characterisation of four bimetallic gold-gallium clusters with Au-Ga rings as a new structural motif in gold cluster chemistry.

Using the newly introduced reducing agent in gold cluster chemistry GaCp, four new bimetallic gold-gallium cluster compounds were synthesised, stabilised by alkylphosphine ligands. The gold core of Au6(GaCl2)4(PEt3)6, Au7(GaCl2)3(P n Pr3)6 and Au13(GaCl2)5(GaCl)(P n Pr2 n Bu)9 is composed of two, three and four Au4 tetrahedra, linked in different ways. This arrangement gives the last-mentioned cluster the shape of a five-pointed star. A fourth synthesised metalloid gold cluster Au13(GaCl2)5(P n Pr3)9 consists of a voluminous gold core encircled by a gold-gallium chain. These gold-gallium chains are present in all four cluster compounds and are similar to the well-known gold-sulphur staple motifs in thiol-stabilised gold cluster compounds.

Nanometer Sized Direct Laser-Induced Gold Printing for Precise 2D-Electronic Device Fabrication.

Flexible electronics manufacturing technologies are essential and highly favored for future integrated photonic and electronic devices. Direct laser induced writing (DIW) of metals has shown potential as a fast and highly variable method in adaptable electronics. However, most of the DIW procedures use silver structures, which tend to oxidize and are limited to the micrometer regime. Here, a DIW technique is introduced that not only enables electrical gold wiring of 2D van-der-Waals materials with sub-µm structures and 100 nm interspacing resolution but is also capable of fabricating photo switches and field effect transistors on various rigid and elastic materials. Light sensitive metalloid Au32 -nanoclusters serve as the ink that allows for low-power cw-laser exposure without further post-treatment. With a simple lift-off procedure, the unexposed ink can be removed. The technique realizes ultrafast, high resolution, and high precision production of integrated electronics and may pave the way for personalized circuits even printed on curved surfaces.

[(thf)5Ln(Ge9{Si(SiMe3)3}2)] (Ln = Eu, Sm, Yb): Capping Metalloid Germanium Cluster with Lanthanides.

We report the synthesis of three neutral complexes with different coordination modes of a di-silylated metalloid germanium cluster to divalent lanthanides [(thf)5Ln(ηn-Ge9(Hyp)2)] (Ln = Yb (1, n = 1); Eu (2, n = 2, 3), Sm (3, n = 2, 3); Hyp = Si(SiMe3)3) by the salt metathesis of LnI2 with K2[Ge9(Hyp)2] in THF. The complexes were characterized by elemental analysis, nuclear magnetic resonance and UV-vis-NIR spectroscopy, and single-crystal X-ray diffraction. In thf solution, the formation of contact or solvate-separated ion pairs depending on the concentration is assumed. Compound 2 exhibits a blue luminescence typical for Eu2+. The solid-state magnetic measurements of compounds 2 and 3 confirm the presence of divalent europium and samarium, respectively.

Oxidative Coupling of [Ge9(Si(SiMe3)3)2]2- with f Elements.

We report the reactions of K2[Ge9(Hyp)2] (Hyp = Si(SiMe3)3) with (thf)3YbI3, ThI4, and UCl4, leading to the oxidative coupling of the metalloid germanium cluster to form the dimeric dianion [Ge18(Hyp)4]2-. The novel dimerized Ge18-cluster was isolated and characterized by single-crystal X-ray diffraction analysis as a component of ionic compounds [Yb(thf)6][Ge18(Hyp)4] (1) and [K(2.2.2-crypt)]2[Ge18(Hyp)4] (2) with two different counterions. The dihedral angle between two intact Ge9 cages depends on the counterions, which was also studied by quantum-chemical calculations.

Multilayer Langmuir Film of Monodisperse Au Nanoclusters: Unusual Growth via Bilayers.

The assembly of nanomaterials into thin films is an important area in the nanofabrication of novel devices. The monodispersity of nanoparticles plays an essential role in the resulting quality of the assembled mono- and multilayers. Larger polydispersity leads to smaller lateral correlation lengths and smaller domains of aligned nanoparticles, thus resulting in more point and line defects. Perfectly monodisperse nanoparticles should therefore minimize the number of defects in the assembled films. Despite tremendous progress in reducing the polydispersity of nanoparticles, there has been limited research on the assembly of thin films out of perfectly monodisperse nanoclusters. Here, we show a formation of Langmuir films using perfectly monodisperse gold nanoclusters with composition Au32(nBu3P)12Cl8 exhibiting a diameter of 1.8 nm. Using both in situ and ex situ small-angle X-ray scattering, we show that the monolayer formed on a Langmuir-Blodgett trough exhibits long-range order. Moreover, after compressing the monolayer, we found that the stress accumulated prior to the monolayer collapse triggers a transition to a short-range order not previously reported. If such monolayer is compressed further, the second layer is not formed as in the case of standard nanoparticles. Instead, a growth of islands by an odd number of layers is observed, leading to a thin film with a structure consisting of two different orientations of the hexagonal lattice. Such anomalous behavior may have implications for the possibilities of thin-film formation.

Substitution of Hyp (Hyp = Si(SiMe3)3) at metalloid [Ge9(Hyp)3]- clusters using phosphine stabilized Au(I)Cl.

We present two new intermetalloid cluster compounds [(nBu3P)AuGe9(Hyp)2Au(PnBu3)]2 (1) and [Au(iPr2POC6H4OPiPr2)AuGe9(Hyp)2]2 (2) which are obtained from the reaction of KGe9(Hyp)3 (Hyp = Si(SiMe3)3) with the respective Au(I) phosphine precursors. The products are characterized via X-ray crystal structure analysis and the reaction course is analysed via NMR spectroscopy. We also show that in the resulting compound 1 the hypersilyl substituents can be reintroduced via the reaction with Hyp-Cl to obtain nBu3PAuGe9(Hyp)3.

Au20 (t Bu3 P)8 : A Highly Symmetric Metalloid Gold Cluster in Oxidation State 0.

Metalloid gold clusters have unique properties with respect to size and structure and are key intermediates in studying transitions between molecular compounds and the bulk phase of the respective metal. In the following, the synthesis of the all-phosphine protected metalloid cluster Au20 (t Bu3 P)8 , solely built from gold atoms in the oxidation state of 0 is reported. Single-crystal X-ray analysis revealed a highly symmetric hollow cube-octahedral arrangement of the gold atoms, resembling gold bulk structure. Quantum-chemical calculations illustrated the cluster can be described as a 20-electron superatom. Optical properties of the compound have shown molecular-like behavior.

Oxidation of [Ge9{Si(SiMe3)3}3]- with LnI3 (Ln = Eu, Sm, Yb): Isomerism of Metalloid Germanium Clusters.

The oxidation of K[Ge9(Hyp)3] (Hyp = Si(SiMe3)3) with lanthanide triiodides LnI3 (Ln = Eu, Sm, Yb) leads to the formation of novel clusters with a Ge18-core isolated as a co-crystallizate of Ge*18(Hyp)6 (1a) and Ge18(Hyp)5(Si(SiMe3)2)(SiMe3) (1b). Clusters 1a and 1b differ distinctly from the known cluster Ge18(Hyp)6 (A), which has been found earlier in the reaction of K[Ge9(Hyp)3] with FeCl2 and now identified as an intermediate product in the production of compounds 1a and 1b. These three compounds A, 1a, and 1b are thus structural isomers being the first example of genuine isomerism in metalloid main-group cluster compounds.

{Ge8[Fe(CO)4]8}7-: an anionic cubic germanium-iron-cluster featuring an unpaired electron.

Within the reaction of a metastable Ge(I)Cl solution and Na2Fe2(CO)8 the anionic cubic cluster compound {(thf)14Na6Ge8[Fe(CO)4]8}- (3) is obtained. The open shell character of 3 is proven by EPR spectroscopy. Quantum chemical calculations furthermore show that also the closed shell systems should be stable, but could not be isolated so far. Additionally, 3 can be seen as an intermediate cluster compound on the formation of metalloid clusters.

Higher stability of metalloid tin clusters obtained via the cation-anion interaction.

The reaction of a metastable SnCl solution with KR (R = Si(SiMe3)2(SitBuMe2) = HyptBuMe2 or Si(SiMe3)2(SiEt3) = HypEt3) gives the metalloid tin cluster [Sn10R4]2- in partly good yields. The tin clusters are in the solid state as well in solution coordinated by a potassium cation, leading first of all to a more static compound and novel coordination polymers in the solid state. Additionally, the coordination of the potassium cation strongly increases the stability of the cluster in solution. This higher stability is thereby an important prerequisite for future investigation of this open shell metalloid tin cluster.

Ge14Br8-xClx(PEt3)4: Insight into the Reaction Route to Metalloid Clusters of Germanium.

The isolation of the germanium mixed halide cluster Ge14Br8-xClx(PEt3)4 (2) by the reaction of a metastable GeIBr solution (toluene/PEt3) with GeCl2·dioxane provides new insights into the complex formation mechanism of metalloid germanium clusters through the disproportionation reaction of GeIX (X = Cl and Br). It is shown that the GeII halide is involved in at least two steps in the build-up reaction of 2. The molecular structure of 2 is presented together with a plausible reaction mechanism leading to the binary cluster Ge14Br8(PEt3)4 and future aspects of these findings.

GeClx[Co(CO)3PR3]4-x (x = 0-3; R = nPr, nBu): from cobalt substituted germanes to novel binary cluster compounds.

The synthesis of a variety of cobalt substituted germanes of the composition GeClx[Co(CO)3PR3]4-x (x = 0-3; R = nPr, nBu) is presented, which can be obtained in average to good yields from a reaction of GeCl2·dioxane and Co2(CO)8 or KCo(CO)4 in the presence of the respective phosphine. Reductive coupling reactions with potassium/benzophenone lead to ligand scrambling while the reductive coupling with Mg/MgBr2 leads to the pseudo-cubic cluster compound Ge7Co(CO)3[Co(CO)3PnBu3]72, showing that the mixed substituted germanes are powerful precursors to this new class of cluster compounds. All compounds are structurally characterized and well observable via NMR and IR spectroscopy.