High-resolution solid-state 119Sn and 195Pt NMR studies of MPtSn semiconductors (M = Ti, Zr, Hf, Th)

Solid-state 119Sn and 195Pt magic-angle spinning (MAS) NMR spectra are reported on a series of MPtSn compounds (M = Ti, Zr, Hf, Th). In favorable cases (TiPtSn and ZrPtSn) the spectra reveal expected J-coupling patterns originating from indirect spin coupling between Pt and Sn nuclei. MAS has no effect on the broad and asymmetric spectra of either 119Sn and 195Pt nuclei in HfPtSn.     

金属核的磁共振研究——Ⅲ锡(Ⅳ)有机化合物的~(119)Sn、~(117)Sn-NMR谱及溶剂配位络合物的形成

本文测定了二十个含有烷基、苯基、烯丙基、五元杂环基及其它极性基团的Sn(Ⅳ)化合物的~(119)Sn、~(117)Sn-NMR谱,讨论了各种取代基对Sn核电子云密度及磁屏蔽的影响,考察了~(119)Sn谱峰随溶剂、浓度、温度的变化,研究了Ph_3SnCl化合物与DMSO配位生成配合物的过程,测出了平衡常数和自由能的变化。     

Double-quantum filtered MAS NMR in the presence of chemical shielding anisotropies and direct dipolar and J couplings

Double-quantum filtered MAS NMR spectra of an isolated homonuclear spin-1/2 pair are considered, at and away from rotational resonance conditions. The pulse sequence used is the solid-state NMR equivalent of double-quantum filtered COSY, known from solution-state NMR. The 119Sn spin pair in [(chex3Sn)2S] is characterized by a difference in isotropic chemical shielding smaller than the two chemical shielding anisotropies and by direct dipolar and isotropic J-coupling constants of similar magnitudes. At rotational resonance, one-dimensional double-quantum filtered 119Sn lineshapes yield the relative orientation of the two 119Sn chemical shielding tensors. Good double-quantum filtration efficiencies are found at and away from rotational resonance conditions, despite the presence of large chemical shielding anisotropies. Numerical simulations illustrate the interplay of the direct dipolar and J-coupling pathways and identify the latter as the main pathway even at rotational resonance conditions.     

Determination of NMR interaction parameters from double rotation NMR

It is shown that the anisotropic NMR parameters for half-integer quadrupolar nuclei can be determined using double rotation (DOR) NMR at a single magnetic field with comparable accuracy to multi-field static and MAS experiments. The (17)O nuclei in isotopically enriched l-alanine and OPPh(3) are used as illustrations. The anisotropic NMR parameters are obtained from spectral simulation of the DOR spinning sideband intensities using a computer program written with the GAMMA spin-simulation libraries. Contributions due to the quadrupolar interaction, chemical shift anisotropy, dipolar coupling and J coupling are included in the simulations. In l-alanine the oxygen chemical shift span is 455 +/- 20 ppm and 350 +/- 20 ppm for the O1 and O2 sites, respectively, and the Euler angles are determined to an accuracy of +/- 5-10 degrees . For cases where effects due to heteronuclear J and dipolar coupling are observed, it is possible to determine the angle between the internuclear vector and the principal axis of the electric field gradient (EFG). Thus, the orientation of the major components of both the EFG and chemical shift tensors (i.e., V(33) and delta(33)) in the molecular frame may be obtained from the relative intensity of the split DOR peaks. For OPPh(3) the principal axis of the (17)O EFG is found to be close to the O-P bond, and the (17)O-(31)P one-bond J coupling ((1)J(OP)=161 +/- 2 Hz) is determined to a much higher accuracy than previously.     

Formation of gold nanoparticles in gold ruby glass: The influence of tin

A ¹¹⁹Sn Mössbauer study was carried out of tin(IV) complexes with 2-benzoylpyridine thiosemicarbazone (H2Bz4DH) and its N(4)-methyl (H2Bz4M) and N(4)-phenyl (H2Bz4Ph) derivatives: [Sn(2Bz4DH)Cl₃] (1), [Sn(2Bz4DH)PhCl₂] (2), [Sn(2Bz4M)Cl₃] (3), [H₂2Bz4M]₂[Ph₂SnCl₄] (4), [Sn(2Bz4Ph)PhCl₂] (5), [Sn(2Bz4Ph)Ph₂Cl] (6), in which H2Bz4R stands for the neutral ligand and 2Bz4R stands for the anionic thiosemicarbazone. In addition, ¹¹⁹Sn Mössbauer studies of the tin(IV) complexes [Sn(H4Bz4DH)₂Cl₄H₂O] (7), [Sn(H4BzPS)₂Cl₄H₂O] (8) with 4-benzoylpyridine thiosemicarbazone (H4Bz4DH) and the correspondent semicarbazone (H4BzPS) were performed. The isomer shifts decrease upon coordination due to the variation in the percentage of s character as tin changes from approximately sp³ hybridization in the tin salts to sp³d² in the octahedral or sp³d³ in the heptahedral complexes. The Mössbauer parameters of compound (4) showed the existence of two tin(IV) sites, which have been attributed to the presence of the cis and trans isomers.     

三环已基羧酸锡的13C和119Sn NMR研究

测定了33个三环己基脂肪族和芳香族羧酸锡在非配位溶剂(CDCl₃)中的¹³C和¹¹⁹Sn NMR谱。结果表明:化学位移δ(¹¹⁹Sn)值主要由锡原子的配位数决定,结构上微小的变化。都能在δ(¹¹⁹Sn)值上明显地表现出来。讨论了不同类型化合物间NMR参数间的关系。     

Ratios of gI-factors and hyperfine structure anomalies of115Sn,117Sn and119Sn

The ratios of the g_I-factors of¹¹⁵Sn,¹¹⁷Sn and¹¹⁹Sn have been measured by the NMR method in different solutions which have large chemical shifts. No primary isotopic effect on the magnetic shielding was found within the error of 7·10^?7. Therefore the ratios have been used for the calculation of the hyperfine structure anomalies in the³P₁,³P₂ and¹D₂ atomic states of the given tin isotopes.     

A pulsed EPR study of the catalytic oxidation of CO over Cu/SnO2

The role of the Cu(II) in the catalytic oxidation of CO over Cu/SnO₂ with low Cu(II) content was studied by continuous wave EPR, electron spin echo envelope modulation (ESEEM) and hyperfine sublevel correlation (HYSCORE) spectroscopes. Three methods were employed for introducing the copper: (i) by coprecipitation, (ii) impregnation onto SnO₂ gel and (iii) impregnation onto calcined SnO₂. Two types of Cu(II) species were identified in these calcined Cu/SnO₂ materials. Those belonging to the first type, termed B and C, exhibit highly resolved EPR spectra with well defined EPR parameters and are located within the bulk of the oxide. The other group comprises a distribution of surface Cu(II) species with unresolved EPR features and are referred to as S. While the latter were readily reduced by CO the former required long exposures at high temperatures (> 673 K). The specific interactions of the different Cu(II) species with CO were investigated through the determination of the¹³C hyperfine coupling of enriched¹³CO. The ESEEM spectra of calcined samples, generated either by coprecipitation or impregnation, show after the adsorption of CO signals at the Larmor frequencies of^{117, 119}Sn and¹³C and at twice these Larmor frequencies. Although these signals indicate that^{117, 119}Sn and¹³C are in the close vicinity of Cu(II), they cannot provide the hyperfine couplings of these nuclei. This problem was overcome by the application of the HYSCORE experiment. The 2D HYSCORE spectra show well resolved cross peaks which provide the hyperfine interaction of these nuclei. Simulations of the HYSCORE spectra yield for^{117, 119}Sn an isotropic hyperfine constant,a _iso, of ±4.0 MHz and an anisotropic component,T _?, of ±2.0 MHz. Pulsed ENDOR spectra also showed^{117, 119}Sn signals which agree with the above values. The¹³C cross peaks yielda _iso=±1.0 MHz andT _?=±2.0 MHz. Similar C cross peaks were observed in spectra of calcined Cu/SnO₂ after the adsorption of CO₂. Based on the same hyperfine couplings in the samples exposed to¹³CO and¹³CO₂ the signals were assigned to surface carbonate species generated by part of the Cu(II) S type species rather then by species B and the role of the Cu(II) in the oxidation process is discussed.     

119Sn Mössbauer Study of as-Deposited Layers Prepared by Co-evaporation of TeO2 and Sn

The deposited layers on glass surface with thickness between 230 and 500 nm were prepared by the chemical reactions of TeO₂ and Sn during vacuum co-deposition, and were characterized as a function of the Sn/Te ratio between 0.5 and 2.8 by ¹¹⁹Sn conversion electron Mössbauer spectroscopy. The as-deposited samples showed amorphous character with very finely dispersed microstructure. The ¹¹⁹Sn Mössbauer spectra of as-deposited samples revealed the dominance of Sn(II) and Sn(IV) states although SnTe was also found when the Sn/Te ratio was high. A monotonous increase of the Sn(II)/Sn(IV) ratio was observed with increasing Sn/Te ratio.     

Dynamic disorder in solid tetrakis(trimethylstannyl)methane, C(SnMe3)4, investigated by one- and two-dimensional variable-temperature119Sn and13C NMR spectroscopy

Modes of molecular reorientation in solid tetrakis(trimethylstannyl)methane, C(SnMe₃)₄, have been investigated by one- and two-dimensional¹³C and¹¹⁹Sn static and magic-angle spinning nuclear magnetic resonance spectroscopy (NMR) in the temperature range from 150 to 290 K. Spectral lineshape fitting of one- and two-dimensional¹¹⁹Sn NMR experiments shows the pseudo-fivefold disorder previously observed by single-crystal X-ray diffraction on C(SnMe₃)₄ to be dynamic disorder (activation energy E_a ? 32 kJmol^?1). A dynamic-disorder model where each tin atom in a C(SnMe₃)₄ molecule occupies the twenty sites of a nearly perfect pentagonal dodecahedron with equal probability agrees best with the experimental solid-state NMR results.     

Mechanosynthesis and characterisation of the Li–Sn system

Intermetallic phases Li–Sn were synthesized by ball-milling and characterized for their structures and electrochemical performances. All phases in Li–Sn binary phase diagram were identified by ¹¹⁹Sn Mössbauer spectroscopy, used as reference materials for the study of lithium insertion into tin-based electrode materials. The observed spectra show two distinct environments of tin; the Sn-rich phases and the Li-rich phases. An example of electrochemical properties of these phases is proposed for Li₂₂Sn₅. Irreversibility of the first cycle is related to the structural change (3D→2D) of this phase.     

The interaction of DNA with organotin(IV) salts and complexes

Ethanol solutions of Alk _n SnCl_4?n (Alk = Me, Et; n = 1–3) added to aqueous calf thymus DNA provoke DNA condensation (even in the presence of added cysteine) possibly through charge neutralization of DNA phosphodiesters by organotin(IV) cations. The structures of tin bonding environments in binary and ternary condensed systems organotin(IV)-DNA and ligand-organotin(IV)-DNA are determined through point-charge model treatment of the ¹¹⁹Sn Mössbauer parameter Δ, while the possible interchain interaction DNA-tin is inferred from the dynamics of ¹¹⁹Sn nuclei through vtMs.     

Solid-State Si, Cd, Sn, and P NMR Studies of II-IV-P2 Semiconductors

Solid-state ²⁹Si, ¹¹³Cd, ¹¹⁹Sn, and ³¹P MAS NMR spectra are reported on a series of II-IV-P₂ compounds. In favorable cases (e.g., high degree of crystallinity, low concentration of unpaired electrons), well-defined spectra, with sharp lines for each specific nearest-neighbor configuration, are observed; in such cases, expected J coupling patterns are also seen. High-resolution solid-state NMR studies of this type provide useful information on structure (disorder), doping, and electron-mediated coupling in semiconductor systems.     

Magnetic hyperfine interactions of 119Sn probe atoms in the binary perovskite CaCu3Mn4O12

The manganite CaCu₃Mn₄O₁₂ doped by ¹¹⁹Sn atoms (about 1 at % with respect to Mn atoms) is studied by Mössbauer spectroscopy. The introduction of diamagnetic tin atoms is found not to affect the structure of the manganite. Tetravalent tin atoms are shown to substitute for the isovalent manganese atoms that are located in an octahedral oxygen surrounding. The cluster method of molecular orbitals is used to calculate the contributions of Mn⁴⁺ and Cu²⁺ cations that belong to different structural sublattices to the hyperfine magnetic field at ¹¹⁹Sn nuclei (H _Sn = 105 kOe at T = 77 K). These partial contributions are analyzed, and the intrasublattice Mn⁴⁺-O-Mn⁴⁺ exchange interactions are found to play a significant role in the formation of the magnetic structure of the manganite.     

A 13C solid-state NMR investigation of the alkynyl carbon chemical shift tensors for 2-butyne-1,4-diol

The alkynyl carbon chemical shift (CS) tensors for 2-butyne-1,4-diol are reported, based on analyses of the carbon-13 NMR spectra of stationary-powder and slow magic-angle spinning (MAS) samples for which the alkynyl carbon nuclei are enriched in 13C. NMR spectra of slow MAS samples exhibit spinning-frequency-dependent fine structure typical of crystallographically equivalent but magnetically distinct nuclei. Simulated spectra of slow MAS samples of this two-spin system are particularly sensitive to the relative orientations of the CS tensors. In addition, the value of 1J(13C, 13C), +175 +/- 10 Hz, is determined by examination of the total NMR lineshape of slow MAS samples. The CS tensors are almost axially symmetric, delta11 = 158.9 +/- 1.0 ppm and delta22 = 155.7 +/- 1.0 ppm; the direction of greatest shielding is approximately along the alkynyl C-C bond, delta33 = -57.8 +/- 2.0 ppm. Both the magnitudes of the principal components of the CS tensors and their orientations are in agreement with those predicted from first-principles calculations at the HF and MP2 levels of theory. This study demonstrates the importance of examining the NMR spectra of homonuclear two-spin systems with and without MAS under a variety of conditions (e.g., two or more applied magnetic fields and slow MAS).     

二茂铁有机锡衍生物的13C,119Sn NMR研究

本文测定了几种二茂铁有机锡衍生物的¹¹⁹Sn,¹³C NMR谱。对其中几种衍生物的¹³C NMR谱进行了归属,从而进一步验证了这类化合物的结构。着重讨论了结构如化合物中取代基X的改变对¹¹⁹Sn化学位移的影响。并对结构如 类化合物N→Sn异侧配位的问题进行了讨论。     

Application of the MAS-J-HMQC experiment to a new pair of nuclei {29Si,31P}: Si5O(PO4)6 and SiP2O7 polymorphs

We report the results of the two-dimensional MAS-J-HMQC experiment providing scalar correlations between 29Si and 31P nuclei in solid state NMR, and we give the first evaluation of the 2JSi-O-P coupling constants (approximately 15 Hz) for a crystalline silicophosphate phase Si5O(PO4)6. The experiment is applied to the characterization of complex mixtures of SiP2O7 phases, through editing of 31P spin pairs by the heteronuclear 2JP-O-Si interaction.     

Chemical transport reactions in the In-Sn-S ternary system: Existence of tin (II) and tin (IV) atoms by Mössbauer effect of119Sn in the isolated compounds

Iodine vapour transport, carried out in the In-Sn-S ternary system leads to single crystals with quite different morphologies: needles, sticks, sheets and polyhedra. The two oxidation states of tin atoms are shown for all these phases by¹¹⁹Sn Mössbauer effect. A varying relative proportion of tin(IV) — tin(II) is observed according to the different crystal forms.     

Investigation of PdSn-catalysts for nitrate removal in drinking water processing

PdSn catalysts prepared by various methods and used for nitrate reduction were investigated by means of in situ _119mSn Mössbauer spectroscopy. Characterization by ^119mSn Mössbauer spectroscopy revealed significant differences concerning the modification of the palladium particles supported on alumina. The controlled surface reaction preparation method (CSR) leads to formation of PdSn alloys with different tin contents besides small amounts of Sn(II) species and unalloyed metallic Sn. On the other hand the impregnation method leads to a small amount of PdSn alloys and higher contents of Sn(II) species. Sn(IV) species were found in both kinds of catalysts. The CSR prepared PdSn catalysts showed an improved activity and selectivity compared to the catalysts obtained by the impregnation method.