119Sn Nuclear Magnetic Resonance Research Articles

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 amino propyl substituted organo tin compounds

In this work, a new synthetic pathway yielding unprotected amino propyl tin compounds is described. For this purpose, mono stannanes with different substitution patterns are used. In a first step, tin hydrides are deprotonated using lithium diisopropyl amide and mixed with an electrophile containing a protected amine in the ω-position. After deprotection via acidic hydrolysis, the desired amino propyl tin compounds are obtained in high yield and purity. The thermal reaction behavior of the amino propyl tin hydrohalide intermediates containing one aromatic residue at the central tin atom is also investigated. For this purpose, amino propyl tin hydrohalides are heated under vacuum until the aromatic hydrocarbon is liberated. This thermal treatment leads to so far unknown tin halides containing an amino propyl side chain. For all of these substances detailed liquid 1H, 13C, and 119Sn-nuclear magnetic resonance (NMR) data were obtained, and in one case solid state NMR is also conducted. Regarding solids, single crystal X-ray analysis is performed. Some derivatization reactions with these new substances are demonstrated, especially the synthesis of an amino propyl tin carboxylate, which might be very interesting for biological, pharmaceutical, or technical processes.

Synthesis, structure and antibacterial activity of some triorganotin(IV) complexes with a benzamidoalanine ligand

New triorganotin(IV) complexes of the type PhSnL3, BuSnL3 and MeSnL3 were constructed with the ligand benzamidoalanine, which was formed by reaction of benzoyl chloride with alanine in the presence of sodium hydroxide. The complexes were characterized by elemental analysis, conductance measurements and infrared, ultraviolet visible and 1H, 13C and 119Sn nuclear magnetic resonance spectroscopy. Monomer structures were proposed from the spectral measurements, with a bidentate form. All compounds were screened for antibacterial (Staphylococcus aureus ATCC-9144, S. epidermidis ATCC-155, Micrococcus luteus ATCC-4698, Bacillus cereus ATCC-11778, Escherichia coli ATCC-25922 and Pseudomonas aeruginosa ATCC-2853) and antifungal (Aspergillus niger ATCC-9029 and A. fumigatus ATCC-46645) activity by paper disc diffusion. The minimum inhibitory concentrations of the compounds were determined by agar streak dilution. MeSnL3 was the most potent antimicrobial agent when compared with ciprofloxin and ketoconazole.We describe here a simple, convenient route for synthesizing new organotin derivatives for antimicrobial evaluation.

μSR and NMR study of the superconducting Heusler compound YPd2Sn

We report on muon-spin rotation and relaxation ($\ensuremath{\mu}$SR) and ${}^{119}$Sn nuclear magnetic resonance (NMR) measurements to study the microscopic superconducting and magnetic properties of the Heusler compound with the highest superconducting transition temperature, YPd${}_{2}$Sn (${T}_{c}=5.4$ K). Measurements in the vortex state provide the temperature dependence of the effective magnetic penetration depth $\ensuremath{\lambda}(T)$ and the field dependence of the superconducting gap $\ensuremath{\Delta}(0)$. The results are consistent with a very dirty $s$-wave BCS superconductor with a gap $\ensuremath{\Delta}(0)=0.85(3)$ meV, $\ensuremath{\lambda}(0)=212(1)$ nm, and a Ginzburg-Landau coherence length ${\ensuremath{\xi}}_{\mathrm{GL}}(0)\ensuremath{\cong}23$ nm. In spite of its very dirty character, the effective density of condensed charge carriers is high compared to that in the normal state. The $\ensuremath{\mu}$SR data in a broad range of applied fields are well reproduced by taking into account a field-related reduction of the effective superconducting gap. Zero-field $\ensuremath{\mu}$SR measurements, sensitive to the possible presence of very small magnetic moments, do not show any indications of magnetism in this compound.

Exploiting Periodic First-Principles Calculations in NMR Spectroscopy of Disordered Solids

Much of the information contained within solid-state nuclear magnetic resonance (NMR) spectra remains unexploited because of the challenges in obtaining high-resolution spectra and the difficulty in assigning those spectra. Recent advances that enable researchers to accurately and efficiently determine NMR parameters in periodic systems have revolutionized the application of density functional theory (DFT) calculations in solid-state NMR spectroscopy. These advances are particularly useful for experimentalists. The use of first-principles calculations aids in both the interpretation and assignment of the complex spectral line shapes observed for solids. Furthermore, calculations provide a method for evaluating potential structural models against experimental data for materials with poorly characterized structures. Determining the structure of well-ordered, periodic crystalline solids can be straightforward using methods that exploit Bragg diffraction. However, the deviations from periodicity, such as compositional, positional, or temporal disorder, often produce the physical properties (such as ferroelectricity or ionic conductivity) that may be of commercial interest. With its sensitivity to the atomic-scale environment, NMR provides a potentially useful tool for studying disordered materials, and the combination of experiment with first-principles calculations offers a particularly attractive approach. In this Account, we discuss some of the issues associated with the practical implementation of first-principles calculations of NMR parameters in solids. We then use two key examples to illustrate the structural insights that researchers can obtain when applying such calculations to disordered inorganic materials. First, we describe an investigation of cation disorder in Y2Ti(2-x)Sn(x)O7 pyrochlore ceramics using (89)Y and (119)Sn NMR. Researchers have proposed that these materials could serve as host phases for the encapsulation of lanthanide- and actinide-bearing radioactive waste. In a second example, we discuss how (17)O NMR can be used to probe the dynamic disorder of H in hydroxyl-humite minerals (nMg2SiO4·Mg(OH)2), and how (19)F NMR can be used to understand F substitution in these systems. The combination of first-principles calculations and multinuclear NMR spectroscopy facilitates the investigation of local structure, disorder, and dynamics in solids. We expect that applications will undoubtedly become more widespread with further advances in computational and experimental methods. Insight into the atomic-scale environment is a crucial first step in understanding the structure-property relationships in solids, and it enables the efficient design of future materials for a range of end uses.

Characterization and Catalytic Properties of Al-MCM-41 Mesoporous Materials Grafted with Tributyltin Chloride

Surface organometallic chemistry (SOMC) is a recently developing research field. It is of great significance for the quantitative modification, restoration of solid surface, identification of the physical and chemical nature of surface and the preparation of new catalyst. The production of R3Sn-O-MCM-41 (R3SnM) was obtained by heating tributyltin chloride and Al-MCM-41 mixture at 170 °C for 5 h under stirring in nitrogen atmosphere. The composition, structure and surface physical and chemical properties of the samples were characterized by inductively coupled plasma mass spectrometry (ICP-MS), 13C, 119Sn, 29Si and 27Al solid state NMR (nuclear magnetic resonance) spectra, in-situ pyridine infrared spectroscopy (Py-IR), N2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), etc. The results of ICP and organic elemental analysis shows that the grafting yield wSn was 6.46% for R3SnM. H0 (the negative logarithm of the acid concentration) and the number of acid sites for R3SnM respectively were 2.77–0.99 and 4.8 mmolg−1 by the Hammett method. N2 adsorption-desorption, XRD, TEM analysis showed that R3SnM with ordered hexagonal mesopore structure, resulted in the decease of surface areas and pore size as well as the increase of mesoporous volume and surface acidity, as compared to Al-MCM-41. R3SnM was used in the synthesis of isoamyl acetate. The yield of isoamyl acetate was 96% when n(isoamyl alcohol): n(acetic acid) 1.0:1.0, wR3SnM = 5%, 138°C for 5 h. The catalyst can be reused and the yield of 86% can be attained when catalyst was reused five times at the same catalytic conditions.

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.

ChemInform Abstract: Application of 119Sn NMR Parameters

Publisher Summary This chapter reviews that the impact of 119Sn nuclear magnetic resonance (NMR) parameters, determined either by 119Sn NMR or in the NMR spectra of other nuclei, on tin chemistry is remarkable. Nowadays, tin chemical shifts coupling constants and nuclear spin relaxation, with respect to the physical principles, is growing. At the same time, the application of more or less sophisticated NMR techniques enables one to monitor the reactions, identify the unstable intermediates, discover their relevance for mechanistic implications, assign the structural features, investigate the intra- and intermolecular dynamic processes, or to compare the structures in the solid and liquid state. 119Sn NMR parameters, in addition to those of the more common nuclei, for example, 1H, 13C, or 31P, add to the attempts at a more complete description of the bonding situation. The chapter suggests that it must be emphasized that the great potential of modern NMR spectrometers can be exploited by a multinuclear approach to obtain a large self-consistent set of NMR data. This also includes the isotope induced chemical shifts and long-range coupling constants that have been neglected in the past.

Structural and Thermophysical Properties of (PbO)0.5(SiO2)0.5Glasses: Effect of SnO2Incorporation

119Sn and 29Si solid-state nuclear magnetic resonance studies on lead silicate glasses containing different amounts of SnO2 confirmed that tin exists in the glass as distorted SnO6 polyhedra and there is no direct interaction between tin and silicon structural units. Transmission electron microscopic studies have established that tin structural units are uniformly distributed in the glass. Significant changes in the values of glass transition temperature, microhardness, and thermal expansion coefficient with SnO2 incorporation into the glass have been attributed to the increased rigidity of the glass network brought about by the replacement of weaker Pb–O linkages with stronger Sn–O linkages.

Mössbauer and NMR characterization of tin octoate: Neat and residues in RTV foams

We have investigated hydrolysis and oxidation effects on tin octoate and on tin-octoate residues in RTV polysiloxane foams by means of Nuclear Magnetic Resonance (NMR) and Mössbauer spectroscopy (MS). 119Sn NMR showed the presence of various tin species whereas 119Sn MS detected the presence of two oxidation states: Sn(II) and Sn(IV). The relative abundance of Sn(IV) increased as both the tin octoate and the foam aged. Foams were also solvent extracted and no selective extraction of one tin oxidation state was observed; both oxidation states were detected. 13C NMR indicated that octanoic acid is present in the tin octoate and in the foams as a residue. MS data showed that aging treatments of the foams and of the neat catalyst have a great effect on the tin oxidation state. The two spectroscopic methods complement each other in following the effects of hydrolysis and oxidation.

Lone-pair effects and structural trends in x SnO·(1 − x)P2O5 glasses deduced from 31P and 119Sn nuclear magnetic resonance

Tin phosphate glasses, of general formula xSnO · (1 − x)P2 O5 (0.3 < x < 0.8),have been prepared by conventional melt-quench techniques and their structuresstudied using 31P and 119Sn nuclear magnetic resonance. The distribution of [PO4]Qnspecies changes with composition in accordance with the simple binary model,and the changes in chemical shift can be explained by the redistribution ofelectron charge from the P = O double bond. Sn(II) is found to occupy a highlyasymmetric site, typical of a sterically active lone pair of electrons. The119Sn parameters of the chemical shift tensor change systematically withx, reflecting thechange in local environment from one where the next nearest neighbours are predominantlyQ2phosphorus to one where they are predominantlyQ0phosphorus.

Organotin complexes with pyrrole-2-carboxaldehyde monoacylhydrazones. Synthesis, spectroscopic properties, antimicrobial activity, and genotoxicity

A series of organotin complexes with pyrrole-2-carboxaldebyde 2-bydroxybenzoylbydrazone (H 3mfps) and pyrrole-2-carboxaldebyde 2-picolinoylbydrazone (H 2mfpp) was investigated. The IR, 1H, and 119Sn nuclear magnetic resonance spectroscopic characterization of all the compounds is reported and discussed in connection with the ligand behaviour of the bydrazone and the structure of the organotin complex. Complexes exhibit antibacterial properties higher than those of the corresponding ligands but they turn out to be less potent than the parent organotin compounds. Sn(H 3mfps) (C 6H 5) 2Cl 2 · 2H 2O and Sn(Hmfpp)(n-C 4H 9) 2Cl are the most active antibacterial compounds showing MIC values between 3–6 μg/ml against Bacillus subtilis and Staphylococcus aureus and between 6–25 μg/ml against Escherichia coli; the first compound also strongly inhibits the growth of Aspergillus niger. All the ligands and complexes are devoid of DNA-damaging activity in the Bacillus subtilis rec-assay. H 2mfpp and its complexes Sn(Hmfpp)(C 2H 5) 2Cl and Sn 3(Hmfpp)(mfpp) (C 6H 5) 3Cl 6 are shown by the Salmonella-microsome assay to be mutagenic substances in the presence of a metabolic activation system. The obtained results are discussed on the basis of structure-activity relationships.

A 119Sn solid-state nuclear magnetic resonance study of crystalline tin sulphides

Non-spinning and magic angle spinning (MAS) 119Sn nuclear magnetic resonance (NMR) spectra of the binary tin sulphides SnS and SnS 2 as well as of a number of stoichiometric compounds from the ternary system Na 2S-SnS 2 have been recorded. The isotropic chemical shift was found to cover a range of more than 800 ppm and allows us to distinguish between different coordination numbers of Sn(IV) present in tin sulphides. Moreover, the chemical shift anisotropy (c.s.a.) is shown to be a sensitive indicator for deformations in the coordination sphere of the tin atom and can be discussed with respect to the known structures of the compounds.

Solid Me 3Sn(O 2CH): molecular and spin dynamics as viewed by 1H, 13C and 119Sn nuclear magnetic resonance spectroscopy

Because of favourable dynamic properties in the solid state, crystalline trimethyltin formate, Me 3Sn(O 2CH), 1, offers quite unique possibilities to probe questions related to molecular dynamics ( 2π 3 Me 3Sn reorientation) and to structural aspects (rigidity of the polymeric backbone, effectively isolated 1H 13C spin pair in the bidentate chain-building formate anion) by 1H, 13C and 119Sn high-resolution solid-state nuclear magnetic resonance (NMR) methods. The combined use of various one- (1D) and two-dimensional (2D) variable-temperature NMR experiments, including consideration of the short-time-cross-polarization (CP) behaviour of the 1H 13C spin pair in 13C-labelled Me 3Sn(O 2 ∗CH), 1 ∗, yields a fairly comprehensive description of the solid-state structure of 1, also in the absence of the single-crystal X-ray structure determination of 1. Taking advantage of the anisotropic polarization transfer within the formate 1H 13C spin pair allows to relate the orientation of the 1H 13C dipolar interaction, i.e. the CH bond direction to the principal axes system of the 13C shielding tensor of the formate 13C from static 13C powder patterns of 1 ∗.

Magnetic Instability of the Gap State in CeNiSn at Very Low Temperature

The low-temperature magnetic property of the gap-type Kondo lattice compound CeNiSn has been investigated down to 0.08 K by the 119 Sn nuclear magnetic resonance (NMR) technique. The temperature dependence of 119 Sn nuclear-spin-lattice relaxation rate (1/ T 1 ) down to 0.4 K was well interpreted by a model that the quasi-particle density of states has a V-shaped structure of the pseudogap proportional to the energy in the vicinity of the Fermi level. Below 0.13 K, however, (1/ T 1 ) is found to decrease exponentially as exp(-Δ/ k B T ) due to the appearance of the energy gap of Δ=0.25 K. The NMR spectrum starts to broaden below 0.13 K, signifying that there develops a static magnetic correlation with a magnetic moment estimated to be as small as 10 -3 µ B / Ce atom. It is suggested that the pseudogap state is changed into the “ spin gap ” state induced by the development of the static magnetic correlation.

1H and 119Sn magnetic resonance study of the SnIV protoporphyrin IX complex of equine myoglobin. Structure of the porphyrin-binding pocket

Tin protoporphyrin IX (SnPP) is being used in the treatment of hyperbilirubinemia. We have studied the SnPP complex with equine myoglobin (EqMb) by 1H and 119Sn nuclear magnetic resonance spectroscopy (NMR) as a general model for SnPP interaction with hemoproteins. The complex formed from SnPP and EqMb, SnPP.EqMb, was found to have essentially the same porphyrin-binding pocket as EqMbCO, including the same porphyrin orientation in the major form of EqMbCO. 119Sn NMR spectroscopy has been used to demonstrate that the proximal His93F8-metal coordination is likely to be intact in SnPP.EqMb. Minor shifts in the side chain positions of some of the residues are indicated, possibly reflecting the presence of water in the sixth coordination site. SnPP.EqMb appears to be stable; it persists at room temperature for weeks and exhibits very slow exchange rates (2H for 1H) for a large number of amide protons in the pH range 7-9.

Structural characterization of sulphur compounds in petroleum fractions by 119Sn nuclear magnetic resonance spectrometry

A method has been developed for the identification of mercaptans in petroleum fractions by reaction with trialkyltin reagents. The derivatives formed have been characterized and quantified by 119Sn n.m.r. spectrometry. Sulphides in petroleum fractions were first reduced to thiols by calcium in liquid ammonia. The thiols were then derivatized with bis(tri-n-butyltin) oxide (TBTO) and characterized in situ by 119Sn n.m.r. spectroscopy. This study also shows that a unique chemical shift may be attributed to each class of sulphydryl-containing compound.

NMR relaxation of tin-119 in pentacoordinate and hexacoordinate environments

Carbon-13 and 119Sn nuclear magnetic resonance spin-lattice relaxation times at 8.48 T and at 4.70 T have been measured at several temperatures for a number of 2,2-di-n-butyl-1,3,2-dioxastannolane derivatives, most of which were prepared from monosaccharide derived diols. The tin nuclei in these compounds, which are at either pentacoordinate or hexacoordinate sites, have 119Sn T1values that are relatively short, between 13 ms and 300 ms. At 8.48 T, chemical shift anisotropy is the only important mechanism for relaxation of the 119Sn nuclei in these compounds. However, at 4.70 T, the 1H,119Sn dipole–dipole mechanism also contributes slightly. The principal components of the 119Sn chemical shift tensor for the pentacoordinate site in the dimeric structure of methyl 4,6-O-benzylidene-2,3-dibutylstannylene-α-D-glucopyranoside (1) were determined directly from the static 119Sn spectrum of a powdered sample and indirectly from slow spinning CP/MAS spectra using both the Herzfeld–Berger procedure and computer simulation. The tin shift tensor for 1 in the solid state is non-axially symmetric with η = 0.49 ± 0.03. The chemical shift anisotropy determined from the solid state experiments, 748 ± 20 ppm, was in good agreement with the value obtained from the solution T1data, 720 ± 50 ppm. For compounds containing both pentacoordinate and hexacoordinate tin atoms, the 119Sn relaxation data indicate that the tin chemical shift anisotropies for the hexacoordinate sites are approximately 1.6 times those of the pentacoordinate sites. Keywords: 119Sn NMR, NMR relaxation, stannylene acetals, 1,3,2-dioxastannolanes.

The structures and reactions of stannylene acetals from carbohydrate-derived trans-diols. Part I. In the absence of added nucleophiles

Di-n-butylstannylene acetals of benzyl 4,6-O-benzylidene-α- and -β-D-glucopyranoside and galactopyranoside have been prepared and studied in solution by 1H, 13C, and 119Sn nuclear magnetic resonance spectroscopy. The species present in solution have been identified from the 119Sn nmr spectral data, by comparison of the 13C nmr chemical shifts of the stannylene acetals and their precursor diols and also by analysis of the products of reactions performed without added nucleophiles. The orientations of the two substituents on the carbons in the pyranose ring attached to the carbons in the stannylene ring determine the structures adopted by the stannylene acetal in solution. If one substituent is axial and the other equatorial, the stannylene acetal exists as a single symmetrical dimer in which the two oxygen atoms in the two 1,3,2-dioxastannolane rings adjacent to the axial substituents are dicoordinate. A stannylene acetal with two adjacent equatorial substituents exists as a non-interconverting mixture of dimers; one with two adjacent axial substituents is present as a rapidly interconverting mixture of dimers, trimers, and tetramers. Benzoylation and benzylation of the latter two types of stannylene acetals have been performed and have been shown to be only slightly regioselective in contrast to the known highly regioselective reactions of the first type. Only when single dimers are present are regiospecific or highly regioselective reactions obtained. The causes of the variation in the species present and of the reaction regioselectivity for different stannylene acetals are discussed. Keywords: stannylene acetals, 1,3,2-dioxastannolanes, 119Sn NMR spectroscopy, regioselective reactions, carbohydrates.

A multinuclear, high-resolution solid-state NMR study of sorensenite (Na4SnBe2(Si3O9)·2H2O) and comparison with wollastonite and pectolite

This paper presents a solid state 1H, 23Na, 29Si, and 119Sn nuclear magnetic resonance (NMR) study of sorensenite. New 29Si NMR data for two related pyroxenoids, wollastonite and pectolite, are included for comparison. By more sensitively probing chemical bonding, the element-specific NMR observations both complement and reinforce the x-ray diffraction results. The role of hydrogen and its interactions with neighboring atoms in sorensenite is further clarified. The wollastonite and pectolite 29Si spectra resolve for the first time all three crystallographic sites and their comparison with sorensenite reveals subtle, systematic differences in sites along the pyroxenoid chains. Effects of corner-shared BeO4 tetrahedra on 29Si shifts show that sorensenite may also be viewed as a more polymerized silicoberyllate.