Solid-state 119Sn Research Articles

Development of Fluoride-Ion Primary Batteries

The primary lithium-carbon monofluoride (Li-CFx) cell offers the highest specific energy of any commercial lithium metal battery chemistry known. However, the practical discharge voltage even at low current densities (ca. 2.5-2.7 V) is significantly lower relative to the theoretical value (4.57 V), causing a significant penalty in specific energy. To reduce the overpotential at the CFx electrode, we altered the electrochemical reaction mechanism to defluorinating the CFx electrode upon discharge, without concomitant lithiation. Here, using a room temperature fluoride-ion (F-ion) conducting electrolyte, we demonstrate the electrochemical defluorination of CFx cathodes paired with either lead (Pb) or tin (Sn) metal anodes for the first time.The primary F-ion Pb-CFx and Sn-CFx cells yielded capacities of 700 mAh g-1 and 400 mAh g-1, without optimization. Importantly, the discharge voltage of the Pb-CFx cell suggested that polarization loss of the cell was reduced by 1 V compared to a Li-CFx cell, indicating that a much higher operating voltage could be achieved with this design. XRD measurements show that the metal fluorides PbF2 or SnF2 form on the Pb or Sn anodes, respectively. Solid-state 19F and 119Sn{19F} NMR measurements of a F-ion Sn-CFx discharged Sn electrode and electrode components revealed the presence of both SnF2 and SnF4, where the latter is the main discharge product. Solid-state 2D 19F{19F} dipolar-correlation NMR experiments of the discharged Sn electrode revealed the amorphous nature of the electrochemically formed SnF4, confirming the reason it was not observed by XRD. The presence of nano-ordered regions with some amorphous in nature is also validated by Raman scattering and surface morphology changes of the electrodes upon discharge. Metal fluorides were discovered on the discharged CFx cathode of both the F-ion Pb-CFx and Sn-CFx cells, as evidenced by XRD, XRF, and solid-state NMR. ICP and XRF, quantified at ca. 5.4%, and ca. 3% contribution to the discharge capacity due to Pband Sn cation transport and reaction. Thus, a two-fold reduction in metal fluoride dissolution, transport, and reaction at the CFx electrode was achieved when using Sn, compared to the Pb.Solid-state 19F NMR measurements of a pristine and discharged CFx electrode from a Sn-CFx cell establish unambiguously that C-F bonds are broken upon discharge. The 19F molar percentage of CF bonds consumed (39%) was compared to the cell capacity extracted related to the theoretic capacity of CFx (36.4%), confirming the electrochemical defluorination of CFx as well as a minor contribution due to Sn2+ cation transport. Overall, we have demonstrated a new electrochemical discharge mechanism relative to conventional Li–CFx cells, which reduces polarization loss and raises the possibility of improvement to a higher practical discharge voltage by using alternative metal anodes. Future work will address the lithium metal counter electrode reactivity to enable a F-ion based Li-CFx cell.

Are Selenides the Same as Sulfides? Structure, Spectroscopy, and Properties of Narrow-Gap Rare-Earth Semiconductors RE2Sn(S1-xSex)5 (RE = La, Ce; x = 0-0.8).

The ternary rare-earth sulfides RE2SnS5 (RE = La-Nd) and the partial solid solutions RE2Sn(S1-xSex)5 (RE = La, Ce; x = 0-0.8) were prepared in the form of polycrystalline samples by reaction of the elements at 900 °C and as single crystals in the presence of KBr flux. They adopt the La2SnS5-type structure (orthorhombic, space group Pbam, Z = 2) consisting of chains of edge-sharing SnCh6 octahedra separated by RE atoms. Although the cell parameters evolve smoothly in RE2Sn(S1-xSex)5, detailed structural analysis by single-crystal X-ray diffraction revealed a pronounced preference for the Se atoms to occupy two out of the three chalcogen sites, which offers a rationalization for why the all-selenide end-members RE2SnSe5 do not form. Solid-state 119Sn NMR spectra confirmed the nonrandom distribution of SnS6-nSen local environments, which could be resolved into individual resonances. The Raman spectra of RE2SnS5 compounds show an intense peak at 307-320 cm-1 assigned to a symmetric A1g mode, which is dominated by Sn-S bonds; the Raman peak intensities varied with Se substitution in La2Sn(S1-xSex)5. Optical diffuse reflectance spectra, band structure calculations, and electrochemical impedance spectra indicated that these compounds are narrow band gap semiconductors; the optical band gaps are insensitive to RE substitution in RE2SnS5 (0.7 eV) but they gradually decrease with greater Se substitution in RE2Sn(S1-xSex)5 (0.7-0.4 eV).

Chemical Behavior and Local Structure of the Ruddlesden-Popper and Dion-Jacobson Alloyed Pb/Sn Bromide 2D Perovskites.

The alloyed lead/tin (Pb/Sn) halide perovskites have gained significant attention in the development of tandem solar cells and other optoelectronic devices due to their widely tunable absorption edge. To gain a better understanding of the intriguing properties of Pb/Sn perovskites, such as their anomalous bandgap's dependence on stoichiometry, it is important to deepen the understanding of their chemical behavior and local structure. Herein, we investigate a series of two-dimensional Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) phase alloyed Pb/Sn bromide perovskites using butylammonium (BA) and 3-(aminomethyl)pyridinium (3AMPY) as the spacer cations: (BA)2(MA)n-1PbxSnn-xBr3n+1 (n = 1-3) and (3AMPY)(MA)n-1PbxSnn-xBr3n+1 (n = 1-3) through a solution-based approach. Our results show that the ratio and site preference of Pb/Sn atoms are influenced by the layer thickness (n) and spacer cations (A'), as determined by single-crystal X-ray diffraction. Solid-state 1H, 119Sn, and 207Pb NMR spectroscopy analysis shows that the Pb atoms prefer the outer layers in n = 3 members: (BA)2(MA)PbxSnn-xBr10 and (3AMPY)(MA)PbxSnn-xBr10. Layered 2D DJ alloyed Pb/Sn bromide perovskites (3AMPY)(MA)n-1PbxSnn-xBr3n+1 (n = 1-3) demonstrate much narrower optical band gaps, lower energy PL emission peaks, and longer carrier lifetimes compared to those of RP analogs. Density functional theory calculations suggest that Pb-rich alloys (Pb:Sn ∼4:1) for n = 1 compounds are thermodynamically favored over 50:50 (Pb:Sn ∼1:1) compositions. From grazing-incidence wide-angle X-ray scattering (GIWAXS), we see that films in the RP phase orient parallel to the substrate, whereas for DJ cases, random orientations are observed relative to the substrate.

Effect of aliovalent bismuth substitution on structure and optical properties of CsSnBr3

Aliovalent substitution of the B component in ABX3 metal halides has often been proposed to modify the band gap and thus the photovoltaic properties, but details about the resulting structure have remained largely unknown. Here, we examine these effects in Bi-substituted CsSnBr3. Powder X-ray diffraction (XRD) and solid-state 119Sn, 133Cs and 209Bi nuclear magnetic resonance (NMR) spectroscopy were carried out to infer how Bi substitution changes the structure of these compounds. The cubic perovskite structure is preserved upon Bi-substitution, but with disorder in the B site occurring at the atomic level. Bi atoms are randomly distributed as they substitute for Sn atoms with no evidence of Bi segregation. The absorption edge in the optical spectra shifts from 1.8 to 1.2 eV upon Bi-substitution, maintaining a direct band gap according to electronic structure calculations. It is shown that Bi-substitution improves resistance to degradation by inhibiting the oxidation of Sn.

Efficient Conversion of Glucose to 5-Hydroxymethylfurfural over a Sn-Modified SAPO-34 Zeolite Catalyst

Efficient and one-pot conversion of biomass-derived carbohydrate into highly value-added 5-hydroxymethylfurfural (HMF) is a crucial reaction step for the valorization of biomass resources toward bio-based chemicals and fuels. In this work, a series of Sn/SAPO-34 catalysts were prepared through impregnation and evaluated in glucose conversion to HMF. The physicochemical properties of Sn/SAPO-34 catalysts were systematically characterized by SEM, XRD, N2 physisorption, XPS, solid-state 119Sn, 29Si, and 31P NMR, XRF, UV–vis, NH3-TPD, and pyridine-FTIR techniques. It was demonstrated that controlling the Sn loading amount could facilely adjust the acid strength and acid amount of the SAPO-34 zeolite. The incorporation of Sn species could induce the formation of a tetrahedrally coordinated Sn4+ site and Sn-OH site to improve the amounts of Bronsted and Lewis acid sites of the catalyst. However, modification with sufficiently high Sn loading could decrease the acid strength and performance of the catalyst owing to its structure damage. The 5%Sn/SAPO-34 catalyst (i.e., Sn loading calculated based on the mass ratio of SnCl4·5H2O as a precursor to the parent SAPO-34) was found to exhibit the superior catalytic performance under mild conditions and could afford an HMF yield of 64.4% at 98.5% glucose conversion in a biphasic 35 wt % NaCl-H2O/tetrahydrofuran (THF) system at 150 °C within 1.5 h. Additionally, a catalytic reaction pathway was proposed, involving the adsorption of glucose molecules by the −Cl group on the catalyst via a hydrogen bond, followed by glucose isomerization to fructose over the Lewis acid Sn4+ and Al3+ sites and, finally, fructose dehydration to HMF catalyzed by the Bronsted acid Sn-OH and Si-OH-Al sites. The activity of the catalyst decreased due to the leaching of the active site Sn after several consecutive cycles. This work provides insights into the improvement in the Sn-containing zeolite catalyst for tandem conversion of glucose to HMF.

Stability and solubility of members of tin perovskites in the schoenfliesite subgroup, [formula omitted](BSn[formula omitted])(OH,O)[formula omitted] (B = Ca, Fe[formula omitted], Mg, Mn[formula omitted], Zn, Cu)

In this work, we determined thermodynamic properties of a suite of tin perovskites □2(BSn4+)(OH,O)6 that correspond to the minerals burtite (B = Ca), jeanbandyite (Fe3+), schoenfliesite (Mg), wickmanite (Mn), vismirnovite (Zn), and mushistonite (Cu). Purity of the samples was verified by powder X-ray diffraction, chemical analysis (ICP-OES), solid state 119Sn magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, 57Fe Mössbauer spectroscopy, thermogravimetry (TG), and Karl-Fischer titration. Enthalpies of formation (ΔfHo) were determined by acid-solution calorimetry (in 5 N HCl at T = 298 K, with SnCl4 as the reference phase), that for jeanbandyite also in high-temperature oxide-melt calorimetry (in sodium molybdate at T = 973 K, with SnO2 as the reference phase). For the two methods, the difference for the ΔfHo values is 10.7 kJ·mol−1, a fair agreement. Because of the high H2O content of the studied phases, acid-solution calorimetry was given preference as it is less sensitive to errors in H2O determination. Entropy was estimated, including configurational or magnetic contribution. The resulting ΔfGo (kJ·mol−1) and logKsp values are: CaSn(OH)6−1885.8±7.6, 7.7; FeSn(OH)5O −1425.4±7.6, −5.8; MgSn(OH)6−1812.4±7.5, 3.3; ZnSn(OH)6−1519.6±7.6, 0.7; MnSn(OH)6−1598.7±7.7, 1.0; CuSn(OH)6−1311.2±7.9, 0.0. The logKsp value relate to reaction MSn(OH)6 + 6H+→ M2+ + Sn4+ + 6H2O or FeSn(OH)5O + 7H+→ Fe3+ + Sn4+ + 6H2O. The solid solution between vismirnovite and mushistonite was found to be thermodynamically non-ideal, with a mixing parameters W=−15.38 kJ·mol−1. Calculations of Gibbs free energies of selected reactions show that the tin perovskites are stabilized at basic pH. For example, burtite becomes stable with respect to cassiterite (SnO2) in systems buffered by calcite, gypsum or the C-S-H phase from cement at pH > 9–10.5. Similarly, jeanbandyite is stabilized in systems buffered by ferrihydrite [Fe(OH)3] but not in those buffered by goethite (FeOOH). Saturation indices calculated from polluted water in field settings show the same trend; the tin perovskites are stable under alkaline conditions and the solutions become supersaturated with respect to the tin perovskites. Hence, under alkaline conditions, such phases could take up and retain tin in the environment.

Magnetism of Kesterite Cu2ZnSnS4 Semiconductor Nanopowders Prepared by Mechanochemically Assisted Synthesis Method.

High energy ball milling is used to make first the quaternary sulfide Cu2ZnSnS4 raw nanopowders from two different precursor systems. The mechanochemical reactions in this step afford cubic pre-kesterite with defunct semiconducting properties and showing no solid-state 65Cu and 119Sn MAS NMR spectra. In the second step, each of the milled raw materials is annealed at 500 and 550 °C under argon to result in tetragonal kesterite nanopowders with the anticipated UV-Vis-determined energy band gap and qualitatively correct NMR characteristics. The magnetic properties of all materials are measured with SQUID magnetometer and confirm the pre-kesterite samples to show typical paramagnetism with a weak ferromagnetic component whereas all the kesterite samples to exhibit only paramagnetism of relatively decreased magnitude. Upon conditioning in ambient air for 3 months, a pronounced increase of paramagnetism is observed in all materials. Correlations between the magnetic and spectroscopic properties of the nanopowders including impact of oxidation are discussed. The magnetic measurements coupled with NMR spectroscopy appear to be indispensable for comprehensive kesterite evaluation.

Solvent and intermolecular nitrogen coordination dictated formation of self-assembled organostannane-macrocycles based on monomers and coordination polymers with unsymmetrical 5-[(E)-2-(4-pyridyl)-1-diazenyl]-2-hydroxybenzoate ligand: Structural topologies and dimensionality

A series of six new organotin(IV) compounds, namely, [nPr3Sn(HL)(MeOH)] 1, [nBu3Sn(HL)]n2, [Bz3Sn(HL)]n3, [Ph3Sn(HL)]n⋅nC6H64, [Ph3Sn(HL)(EtOH)] 5 and [nBu2Sn(L)]n6 were synthesized by reacting appropriate tri- and di-organotin(IV) precursors with the flexible pro-ligand 5-[(E)-2-(4-pyridyl)-1-diazenyl]-2-hydroxybenzoic acid. Their solid-state structures were deduced from single crystal X-ray diffraction data and, in the case of compound 6, also by solid-state 13C and 119Sn NMR spectroscopy. Compounds 1 and 5 are mononuclear as a consequence of methanol/ethanol coordination preventing the propagation of the polymers. The monodentate oxygen atom from the carboxylate group of HL− and the tin-coordinated oxygen atom of alcohol are situated at the axial positions, while Sn-R substituents are at the equatorial sites, defining the distorted trigonal-bipyramidal coordination polyhedron. Both 1 and 5 form one-dimensional (1D) chains created by virtue of O−Hsolv⋯Npy hydrogen bonding interactions, and antiparallel running chains in 1 furnish 34-membered dinuclear macrocyclic rings occupied by SnPr3 groups. Compounds 2–4 feature a one-dimensional coordination polymer facilitated by intermolecular N→Sn bond formation with the pyridyl substituent of LH−. The axially located OOCO and Npy donor atoms and equatorial Sn-R groups give rise to a trigonal-bipyramidal geometry. While similar coordination geometries are observed for 2–4, the tri-n-butyl derivative 2 generates 60-membered macrocyclic rings where four n-butyl groups from two neighboring molecules occupy the cavities. The triphenyltin analogue 4 forms two-dimensional layers with voids filled by benzene solvate molecules, and the sterically demanding tribenzyltin groups in compound 3 result in only relatively weak C−H⋯π, C−H⋯N and van der Waals contacts. On the other hand, compound 6 is a two-dimensional (2D) coordination polymer displaying a distorted pentagonal-bipyramidal geometry around the tin atom where four oxygen atoms of two ligand molecules and the nitrogen atom of a ligand constitute the equatorial plane, while the carbon atoms of the n-butyl groups complete the axial positions. The molecules of 6 self assembled to an interesting dimeric tecton based on a four-membered Sn2O2 ring, generating large 48-membered hexanuclear macrocycles, where the cavities are filled by four di-n-butyl groups from two neighboring molecules. The solution behaviors of compounds 1–5 were judged from the results of the 119Sn NMR spectroscopic characterization.

Cyclic Distannene or Bis(stannylene) with a Ferrocenyl Backbone: Synthesis, Structure, and Coordination Chemistry.

1,1'-Dilithioferrocene was reacted with 2 equiv of isopropyl (Ar*) or methyl (Ar') substituted terphenyl tin(II) chloride. Reaction product 1, carrying the bulkier terphenyl substituent Ar*, displays a bis(stannylene) structure in the solid state without formation of a tin-tin bond. Temperature-dependent solution 119Sn NMR spectroscopy, however, revealed a dynamic interplay between bis(stannylene) (100 °C) and cyclic distannene (-80 °C). In contrast to 1, the less bulky Ar' substituent results in a cyclic distannene 2. On the basis of temperature-dependent 119Sn NMR spectroscopy the Sn-Sn bond of compound 2 was preserved up to 100 °C. Both compounds were further characterized by solid-state 119Sn NMR spectroscopy as well as 119Sn and 57Fe Mössbauer spectroscopy. 1 reacted as a chelating ligand with nickel and palladium complexes [Ni(cod)2] and [Pd(nbe)3] (nbe = norbornene). In the resulting coordination compounds the nonstabilized stannylene acts as a donor as well as an acceptor ligand and shows a dynamic switch from donor to acceptor behavior in the monopalladium complex.

Shape Control of Colloidal Cu2-x S Polyhedral Nanocrystals by Tuning the Nucleation Rates.

Synthesis protocols for colloidal nanocrystals (NCs) with narrow size and shape distributions are of particular interest for the successful implementation of these nanocrystals into devices. Moreover, the preparation of NCs with well-defined crystal phases is of key importance. In this work, we show that Sn(IV)-thiolate complexes formed in situ strongly influence the nucleation and growth rates of colloidal Cu2–xS polyhedral NCs, thereby dictating their final size, shape, and crystal structure. This allowed us to successfully synthesize hexagonal bifrustums and hexagonal bipyramid NCs with low-chalcocite crystal structure, and hexagonal nanoplatelets with various thicknesses and aspect ratios with the djurleite crystal structure, by solely varying the concentration of Sn(IV)-additives (namely, SnBr4) in the reaction medium. Solution and solid-state 119Sn NMR measurements show that SnBr4 is converted in situ to Sn(IV)–thiolate complexes, which increase the Cu2–xS nucleation barrier without affecting the precursor conversion rates. This influences both the nucleation and growth rates in a concentration-dependent fashion and leads to a better separation between nucleation and growth. Our approach of tuning the nucleation and growth rates with in situ-generated Sn–thiolate complexes might have a more general impact due to the availability of various metal–thiolate complexes, possibly resulting in polyhedral NCs of a wide variety of metal–sulfide compositions.

Multinuclear NMR and crystallographic study of diorganotin valproates – Part II

The reactions of SnR2Cl2 {R=Me, Bu and Ph} and sodium valproate, NaO2CCH(CH2CH2CH3)2, NaOVp yielded three diorganotin valproates [{(Me2SnOVp)2O}2] (1), [{(Bu2SnOVp)2O}2] (2) and [{PhSn(O)OVp}6] (3). These stannoxanes have been authenticated in terms of infrared, 1H and 13C NMR, and solution- and solid-state 119Sn NMR and 119Sn Mössbauer spectroscopy. In addition the crystallographic structures of complexes (1)–(3) have been determined by X-ray diffraction. Complexes (1) and (2) displayed two major signals in the 119Sn NMR spectra in solution corresponding to the exo and endocyclic SnR2 moiety of the stannoxanes. Other minor resonances have been also observed due to dynamic processes in solution. However in the 119Sn MAS-NMR experiments only two down field signals were detected for complex (1), according to the presence of the exo and endocyclic organotin fragments, but with different resonance in comparison with the chemical shift obtained in solution. On the other hand little difference was observed in the 119Sn chemical shift of complex (3) since only one resonance was detected in solution- or in the solid-state experiments, and the signals are very close to each other.

Multinuclear NMR and crystallographic studies of triorganotin valproates and their in vitro antifungal activities

The reactions of triorganotin chlorides and sodium valproate, Na(OVp), yielded three triorganotin valproates [{SnMe3(OVp)}n] (1), [{SnBu3(OVp)}n] (2) and [SnPh3(OVp)] (3). All complexes have been authenticated in terms of infrared, 1H and 13C NMR, and solution- and solid-state 119Sn NMR, 119Sn Mössbauer and X-ray crystallography. The 119Sn NMR experiments provided important informations concerning the structures of (1)–(3) in solution and in the solid state. The X-ray experiments revealed the double-polymeric chain of complex (1), in which the geometry at the Sn(IV) is trigonal bipyramidal with intermolecular valproate bridges. The structure of complex (3) was re-determined and the new data show the tin cation at the centre of a distorted trigonal bipyramid, and not coordinated by four electron donating groups. The biological activity of all derivatives has been screened in terms of IC50 (μmolL−1) against C. albicans (ATCC 18804), C. tropicalis (ATCC 750), C. glabrata (ATCC 90030), C. parapsilosis (ATCC 22019), C. lusitaniae (CBS 6936) and C. dubliniensis (clinical isolate 28). Complex (3) exhibited the best biocide activity.

(NH4)4Sn2S6·3H2O: Crystal Structure, Thermal Decomposition, and Precursor for Textured Thin Film

Understanding the condensation of the dimeric thiostannate(IV) [Sn2S6]4– to SnS2 is of key importance for the development of solution processing of advanced tin(IV) sulfide based electronic devices such as photovoltaics (e.g., Cu2ZnSnS4, CZTSSe) and thin-film transistors. Here, we report the crystal structure of tetraammonium thiostannate(IV) trihydrate ((NH4)4Sn2S6·3H2O), which can be used as a more environmentally friendly alternative to the hydrazinium analogue in solution processed advanced tin(IV) sulfide based electronic devices, e.g., CZTSSe. Hirshfeld surface analysis shows that crystal bound water molecules play a significant role in the structure and interact strongly with the sulfur atoms in the dimeric thiostannate(IV) complex [Sn2S6]4–. The thermal decomposition and corresponding condensation of ((NH4)4Sn2S6·3H2O) to SnS2 have been studied by TG/DSC-MS and solid-state 119Sn MAS NMR. It involves the formation of the relatively more condensed thiostannate(IV) complex [Sn4S10]4– at 90 °C via eva...

Analysis of Lead Carboxylates and Lead-Containing Pigments in Oil Paintings by Solid- State Nuclear Magnetic Resonance

ABSTRACTSoap formation in traditional oil paintings occurs when heavy-metal-containing pigments, such as lead white, 2Pb(CO3)2·Pb(OH)2, and lead-tin yellow type I, Pb2SnO4, react with fatty acids in the binding medium. These soaps may form aggregates that can be 100-200 μm in diameter, which swell and protrude through the paint surface, resulting in the degradation of the paint film and damage to the integrity of the artwork. In addition, soap formation has been reported to play a role in the increased transparency of paint films that allows the painting support, the preparatory drawing, and the artists’ alterations to become visible to the naked eye. The factors that trigger soap formation and the mechanism(s) of the process are not yet well understood. To elucidate these issues, chemical and structural information is necessary which can be obtained by solid-state 207Pb, 119Sn, and 13C nuclear magnetic resonance (NMR). In the present study, a combination of 207Pb NMR pulse sequences was used to determine accurately the NMR parameters of lead-containing pigments and lead carboxylates known to be involved in soap formation, such as lead palmitate, lead stearate, and lead azelate. These results show that the local coordination environment of lead azelate is different from lead palmitate or lead stearate and therefore it is unlikely that lead azelate would be incorporated into an ordered structure containing lead palmitate and lead stearate. In addition, the chemical shifts of the pigments obtained are different from those of the soaps, demonstrating that 207Pb NMR is useful in characterizing the components when present in a mixture, such as a paint film. The NMR methods discussed can also be applied to other Pb-containing cultural heritage materials, electronic and optoelectronic materials, superconducting materials, and environmentally contaminated materials.

Novel Organotin(IV) Schiff Base Complexes with Histidine Derivatives: Synthesis, Characterization, and Biological Activity

Five novel tin Schiff base complexes with histidine analogues (derived from the condensation reaction between L-histidine and 3,5-di-tert-butyl-2-hydroxybenzaldehyde) have been synthesized and characterized. Characterization has been completed by IR and high-resolution mass spectroscopy, 1D and 2D solution NMR (1H, 13C and 119Sn), as well as solid state 119Sn NMR. The spectroscopic evidence shows two types of structures: a trigonal bipyramidal stereochemistry with the tin atom coordinated to five donating atoms (two oxygen atoms, one nitrogen atom, and two carbon atoms belonging to the alkyl moieties), where one molecule of ligand is coordinated in a three dentate fashion. The second structure is spectroscopically described as a tetrahedral tin complex with four donating atoms (one oxygen atom coordinated to the metal and three carbon atoms belonging to the alkyl or aryl substituents), with one molecule of ligand attached. The antimicrobial activity of the tin compounds has been tested against the growth of bacteria in vitro to assess their bactericidal properties. While pentacoordinated compounds 1, 2, and 3 are described as moderate effective to noneffective drugs against both Gram-positive and Gram-negative bacteria, tetracoordinated tin(IV) compounds 4 and 5 are considered as moderate effective and most effective compounds, respectively, against the methicillin-resistant Staphylococcus aureus strains (Gram-positive).

Solid-state 119Sn NMR and M¨ossbauer Spectroscopic Studies of the Intermediate-valent Stannide CeRuSn

The ternary stannide CeRuSn is a static mixed-valent cerium compound with an ordering of trivalent and intermediate-valent cerium on two distinct crystallographic sites. 119Sn Mössbauer spectra showed two electronically almost identical tin atoms at 323 K, while at 298 K and below (77 and 4:2 K) two tin sites can clearly be distinguished. Solid-state 119Sn NMR experiments were performed to probe the local hyperfine fields at the two different Sn sites. Powder 119Sn NMR spectra are nicely fitted with two Sn sites with nearly the same magnetic anisotropy, but with different absolute shift values. Both Sn sites are strongly affected by crossover-like transitions between 100 and 280 K. This local-site study confirms the superstructure modulations found in previous investigations. Towards lower temperatures the powder NMR spectra are broadened giving strong precursor evidence for the antiferromagnetically ordered ground state.

Synthesis and structure of pentamethylcyclo­pentadienyltin(II) tetraphenylborate

The title compound (Cp*Sn)BPh4 was obtained by the metathesis reaction of Cp*SnCl with NaBPh4 and ­characterized by single crystal X-ray diffraction as well as solution and solid-state 119Sn nuclear magnetic resonance (NMR) spectroscopy. The coordination modes are best described as (η5-C5Me5)Sn(μ-η6-Ph)2BPh2.

Preparation of clay-supported Sn catalysts and application to Baeyer–Villiger oxidation

Clay-intercalated Sn catalysts were prepared by a conventional cation-exchange method and used for the Baeyer–Villiger oxidation of various ketones with hydrogen peroxide as an oxidant. The intercalation of monomeric Sn species into the clay interlayer was monitored by solid-state 7Li MAS NMR. Solid-state 119Sn MAS NMR and Sn K-edge XAFS analysis revealed that an isolated Sn species, such as [SnIV(OH)x(H2O)5−x](4−x)+ (x = 0–3), was formed in the clay interlayers. Our clay-intercalated Sn catalysts showed extremely high performance in Bayer–Villiger oxidation and were also reusable without any significant loss of activity or selectivity.

Cobalt, Rhodium, Iridium, and Ruthenium Carbonyl Complexes with Stanna-closo-dodecaborate:103Rh NMR,119Sn Mössbauer Spectroscopy, and Solid-State119Sn NMR

Depending on the stoichiometry stanna-closo-dodecaborate [SnB11H11]2– reacts with the dimeric carbonyl complex [Rh(CO)2Cl]2 to give a dinuclear rhodium coordination compound with bridging tin ligands, [Et3MeN]6[Rh2(CO)4(SnB11H11)4] (1), or a pentagonal-bipyramidal complex, [Et4N]5[Rh(CO)2(SnB11H11)3] (2), with the carbonyl ligands in axial position. The analogous iridium and cobalt complexes [Et4N]5[Ir(CO)2(SnB11H11)3] (3) and [Me4N]5[Co(CO)2(SnB11H11)3] (4) exhibit a pentacoordinated structure with the tin ligands in axial positions. The dimeric ruthenium chlorocarbonyl complex [Ru(CO)3Cl2]2 reacts with four equivalents of the tin nucleophile to give the octahedrally coordinated ruthenium complex [Et3MeN]4[Ru-cis-(CO)2-cis-Cl2-trans-(SnB11H11)2] (5). The synthesized coordination compounds were characterized by X-ray crystal structure analysis, by 103Rh, 119Sn, and 11B NMR spectroscopy in solution, and in the case of the rhodium complexes 1 and 2 by 119Sn solid-state NMR and 119Sn Mössbauer spectroscopy.

Study on the Defect Structure of SnO2:F Nanoparticles by High-Resolution Solid-State NMR

In this contribution the preparation and structural characterization of nanoscale fluorine doped tin-oxide (SnO2:F, FTO) is described. By using a microwave assisted polyol approach, nanoparticles with different doping levels are prepared, which show narrow size distribution as measured by X-ray diffraction, electron microscopy and dynamic light scattering. They were converted into electrically conductive optically transparent films at 500 °C by a specific thermal treatment (500 °C in air followed by 250 °C in forming gas), exhibiting a specific resistivity of (1.9 × 10−1 Ω cm). Solid-state MAS NMR and 119Sn Mossbauer spectroscopy were used to study how F atoms are incorporated into the SnO2:F nanoparticles. Distance constraints were determined by 119Sn{19F} REDOR, fluorine-doping homogeneity by homonuclear dipolar recoupling experiments (SR662). Cross-polarization was used to investigate the immediate environment of the dopant. The experiments were supplemented by first-principles quantum-chemical calcula...