Search

In this study, we present a new approach for the synthesis of Pt/SnO2 catalysts using microwave radiation. Pt(IV) and Sn(IV) inorganic precursors (H2PtCl6 and SnCl4) and ammonia were used, which allowed the controlled formation of platinum particles on the anisotropic SnO2 support. The synthesized Pt/SnO2 samples are mesoporous and exhibit a reversible physisorption isotherm of type IV. The XRD patterns confirmed the presence of platinum maxima in all Pt/SnO2 samples. The Williamson-Hall diagram showed SnO2 anisotropy with crystallite sizes of ~10 nm along the c-axis (< 00l >) and ~5 nm along the a-axis (< h00 >). SEM analysis revealed anisotropic, urchin-like SnO2 particles. XPS results indicated relatively low average oxidation states of platinum, close to Pt metal. 119Sn Mössbauer spectroscopy indicated electronic interactions between Pt and SnO2 particles. The synthesized samples were used for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of excess NaBH4. The catalytic activity of the Pt/SnO2 samples for the reduction of 4-NP to 4-AP was optimized by varying the synthesis parameters and Pt loading. The optimal platinum loading for the reduction of 4-NP to 4-AP on the anisotropic SnO2 support is 5 mol% with an apparent rate constant k = 0.59 × 10–2 s–1. The Pt/SnO2 sample showed exceptional reusability and retained an efficiency of 81.4% after ten cycles. [ABSTRACT FROM AUTHOR]

Dolomite-type MSn(BO3)2 phases for M = Mn, Fe, Co and Ni have been synthesized using solid-state synthesis carried out in sealed quartz tubes. X-ray powder diffractiondata Rietveld refinements confirm the rhombohedral space group R 3 ‾ for all compositions. The change in unit-cell parameters follows the increasing nature of the radius of the M-cations. Both the MO6 and SnO6 octahedra are found to be quite regular. 119Sn Mössbauer spectroscopy investigations complement the almost undistorted nature of the SnO6 octahedra and the tetra-valent charge of the tin-atoms. Detailed vibrational features are described from the Raman and the FTIR spectral data collected at ambient conditions. The frequency shifts of some selective Raman and IR bands are explained in terms of the change of cationic sizes and the respective M–O bond distances. The UV/Vis diffuse reflectance data are analyzed using the RATD method, leading to direct bandgaps for all the investigated samples. The wide bandgap semiconductors (3 – 4 eV) show increasing transition energies with increasing cation sizes of the high-spin M-cations in the dolomite types. [ABSTRACT FROM AUTHOR]

A series of cis-bis{5-[(E)-2-(aryl)-l-diazenyl]quinolin-8-olato(dimethyltin(IV), Me2Sn(L)2, and chloro-{5-[(E)-2-(aryl)-l-diazenyl]quinolin-8-olato}dimethyltin(IV), Me2SnCl(L), complexes have been synthesized by reacting the sodium salts of 5-[(E)2-(aryl)-l-diazenyl)quinolin-8-ol (LH) and dimethyltin dichloride in 2:1 and 1:1 molar ratios, respectively. These complexes have been characterized by 1H, 13C, 119Sn NMR in solution and by IR and 119Sn Mössbauer spectroscopy in the solid state. The structures of two of the dimethyltin(IV) complexes, viz., Me2Sn(L2)2 (2) and Me2SnCl(L3). C7H8 (6) (L2 = 5-[(E)-2-(4'-methoxyphenyl)-l-diazenyl)quinolin-8-olate, L3 = 5-[(E)-2-(4'-ethoxy-phenyl)-l-diazenyl)quinolin-8-olate), were determined by single crystal X-ray diffraction. In general, the Me2Sn(L)2 complexes were found to adopt a distorted crá-octahedral arrangement, while Me2SnCl(L) complexes have a distorted trigonal bipyramidal coordination geometry around the tin atom in solution and in the solid state. [ABSTRACT FROM AUTHOR]

Abstract: New organotin(IV) complexes of 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) and 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine (dptp) with 1:1 and/or 1:2 stoichiometry were synthesized and investigated by X-ray diffraction, FT-IR and 119Sn Mössbauer in the solid state and by 1H and 13C NMR spectroscopy, in solution. Moreover, the crystal and molecular structures of Et2SnCl2(dbtp)2 and Ph2SnCl2(EtOH)2(dptp)2 are reported. The complexes contain hexacoordinated tin atoms: in Et2SnCl2(dbtp)2 two 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine molecules coordinate classically the tin atom through N(3) atom and the coordination around the tin atom shows a skew trapezoidal structure with axial ethyl groups. In Ph2SnCl2(EtOH)2(dptp)2 two ethanol molecules coordinate tin through the oxygen atom and the 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine molecules are not directly bound to the metal center but strictly H-bonded, through N(3), to the of the ethanol moieties; Ph2SnCl2(EtOH)2(dptp)2 has an all-trans structure and the C–Sn–C fragment is linear. On the basis of Mössbauer data, the 1:2 diorganotin(IV) complexes are advanced to have the same structure of Et2SnCl2(dbtp)2, while Me2SnCl2(dptp)2 to have a regular all-trans octahedral structure. A distorted cis-R2 trigonal bipyramidal structure is assigned to 1:1 diorganotin(IV) complexes. The in vitro antibacterial activities of the synthesized complexes have been tested against a group of reference pathogen micro-organisms and some of them resulted active with MIC values of 5μg/mL, most of all against staphylococcal strains, which shows their inhibitory effect. [Copyright &y& Elsevier]

Two coordination octahedral Sn(IV) complexes [Sn(L)] and cis-[SnCl(L)(dmso)], where HL is 2-hydroxyacetophenone ( S-benzydithiocarbazate), were prepared and characterized by elemental analysis, IR, NMR (H, C), Sn Mössbauer spectroscopies and X-ray diffraction techniques to investigate their structural properties. Both crystallize in the Monoclinic system, with parameters: a = 8.1905(3), b = 30.8811(15), c = 12.8959(7) Å, β = 94.465(3)° and Z = 4 for [Sn(L)] and a = 8.5247(2), b = 21.5445(7), c = 12.3706(3) Å, β = 96.932(2)° and Z = 4 for cis-[SnCl(L)(dmso)]. In both complexes, the Sn(IV) central atom is coordinated in a distorted octahedral geometry with the thiolate ligand (L) coordinated via O, N and S atoms. The Sn Mössbauer spectroscopy of the complexes were studied and the results revealed that both complexes posses isomer shift ( δ) and quadrupole splitting (Δ), which are almost the same. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: A mixture between cobalt oxalate, tin oxalate and dispersed polyacrylonitrile (PAN) molecules has been used as a new electrode active material for lithium ion batteries. The electrode shows good capacity retention in the case that the imposed potential limit is below 2.0V. The mechanism of the reaction with lithium was studied by using XRD and 119Sn Mössbauer spectroscopy. The electrode materials become irreversibly amorphous at the beginning of the reaction, when tin oxalate is decomposed and Sn(IV) is detected. Then, the metallic ions are reduced and amorphous tin–cobalt phases are formed. Finally, previously unknown Liph name="sbnd" />Sn phases are reversibly formed near 0.0V. The oxalate groups and the PAN form an electrochemically inert matrix. Due to the matrix, the aggregation of the amorphous particles into crystalline particles upon cycling is avoided. The extraction of lithium at the potential values near 2.0V yields to tin–oxygen interactions and this feature disturbs the matrix and yields to capacity fade. [Copyright &y& Elsevier]

Abstract: Novel organotin(IV) derivatives of guanine of the general formula, R2Sn(HGu)2 (where, R=Me (1), n-Bu (2) and Ph (3)) have been synthesized by the reaction of R2SnCl2 with sodium salt of guanine (H2Gu or 2-amino-6-hydroxypurine). The IR spectral studies suggest that guanine acts as a monobasic ligand coordinating through N(9) after its deprotonation. The weak bonding through C(6)o be evidenced, whereas 119Sn Mössbauer data suggest that the coordination number of tin is superior than four. The polyhedron around tin in R2Sn(HGu)2 is distorted trigonal–bipyramidal or pseudo-tetrahedral involving very weak interaction from Cf neighboring molecule leading to polymerized structure. All the compounds exhibited potent anti-inflammatory activity with no appreciable side effects on blood pressure as evidenced by their very mild cardiovascular activity. [Copyright &y& Elsevier]

Abstract: Tin-based intermetallic compounds of different compositions and with micro and nano-sized particles are studied as electrodes for lithium ion batteries. Crystalline microsized particles of CoSn x are obtained at high temperatures, while crystalline nano-sized particles are obtained at low-temperature following a one-pot method which is based on TEG solvent and reduction with NaBH4. The observed capacities of CoSn x compounds in lithium test cells depend on the tin content, electrochemical cycling conditions and crystallite size. The change of the 119Sn Mössbauer isomer shift upon the electrochemical reaction with lithium is more limited for the intermetallic compounds CoSn x than for pure Sn. Nano-sized CoSn x materials show superior specific capacity than microsized CoSn x powders. The maximum observed reversible capacity of nano-Co3Sn2 is equal to 544mAhg−1 in the first cycle, while 413mAhg−1 were observed for nano-CoSn. [Copyright &y& Elsevier]

Abstract: Some new diorganotin(IV) derivatives of the formulae, R2SnL, where R=Me, n-Bu, Ph, and n-Oct, and L is the dianion of histidinylalanine (H2L-1) and histidinylleucine (H2L-2) have been synthesized by the reaction of R2SnCl2 and the preformed sodium salt of the respective dipeptides. The bonding and coordination behaviour in these derivatives are discussed on the basis of FT-IR, multinuclear 1H, 13C and 119Sn NMR and 119Sn Mössbauer spectroscopic studies. These investigations suggest that dipeptides in R2SnL act as dianionic tridentate coordinating through the COO−, NH2 and N− peptide groups. The 119Sn Mössbauer studies, together with the NMR data, suggest a trigonal bipyramidal geometry around tin in R2SnL with the alkyl/aryl groups and in the equatorial positions, while a carboxylic oxygen and the amino nitrogen atom occupy the axial positions. [Copyright &y& Elsevier]

Abstract: New di- and triorganotin(IV) derivatives of tyrosinylphenylalanine (H2Tyr-Phe) with general formulae R2Sn(Tyr-Phe) where R=Me,n-Bu, n-Oct and Ph, and R3 ′Sn(HTyr-Phe) where R′ =Me and Ph have been synthesized. The bonding and coordination behaviour in these derivatives are discussed on the basis of FT-IR, multinuclear 1H, 13C and 119Sn NMR and 119Sn Mössbauer spectroscopic studies. These investigations suggest that dipeptide in R2Sn(Tyr-Phe) acts as dianionic tridentate coordinating through −C(O)O−, –NH2 and (–CO)N− peptide groups while in case of R′ 3Sn(HTyr-Phe) the ligand acts as monoanionic bidentate coordinating through –C(O)O− and –NH2, and the polyhedron around tin in R2Sn(Tyr-Phe) and R′ 3Sn(HTyr-Phe) is a distorted trigonal-bipyramidal. It is further confirmed by the single crystal X-ray structure of Me2Sn(Tyr-Phe)·MeOH which shows two methyl groups and peptide nitrogen (N− peptide) in the equatorial positions, while the two axial positions are occupied by the carboxylic oxygen (O− carboxyl) and the amino nitrogen (Namino) atom from the same ligand molecule. One methanol molecule is also present in the asymmetric unit. [Copyright &y& Elsevier]

Some new di- and triorganotin(IV) derivatives of the formulae, R2SnL, where R =Me, Ph, and n-Oct, and L is the dianion of histidinylleucine (H2L abbreviated as H2(His-Leu)) and R′3 SnHL, where R′ = Me and Ph, HL = monoanion of histidinylleucine, have been synthesized. The bonding and coordination behaviour in these derivatives are discussed on the basis of FT-IR and 119Sn Mössbauer spectroscopic studies. The 119Sn Mössbauer studies, together with the IR data suggest that the ligand in R2Sn(His-Leu) acts as dianionic tridentate coordinating through C(O)O − , –NH2 at axial positions and Npeptide at equatorial position while in case of R′3Sn(HHis − Leu) the ligand acts as a monoanionic bidentate coordinating through C(O)O − and –NH2 giving a distorted trigonal–bipyramidal environment around tin. [ABSTRACT FROM AUTHOR]

Abstract: Cobalt–tin and cobalt–tin–carbon composite electrodes with different nominal compositions (CoSn, CoSn2, CoSn3, CoSn4, CoSn15 and [CoSn3]0.6C0.4) have been prepared by annealing of the elements under an argon flow. 119Sn Mössbauer spectra have been recorded. As a consequence of the electronic transfer from tin atoms to the resulting cobalt–tin intermetallic compounds, the isomer shift barycentre is moved to lower values as compared to pure tin (δ =2.5mm/s). The lower isomer shift values (δ ∼2.0mm/s) for cobalt–tin samples with cobalt to tin atomic ratio equal to 1:3 are obtained for a preparation temperature between 450 and 750°C. In contrast, the presence of carbon atoms limits the isomer shift of the tin-based intermetallic phases, with δ =2.2mm/s for [CoSn3]0.6C0.4 nominal composition in the 450–750°C range, and then the electronic transfer from tin atoms to the resulting intermetallic phase is reduced. The carbon atoms exert an effect in the isomer shift value (increase of δ) that is in opposition to the effect exerted by lithium and cobalt atoms (decrease of δ). After treating with a hydrochloric acid aqueous solution, the 119Sn Mössbauer spectra are less broadened and the electrochemical behaviour in lithium cells is greatly improved. Reversible specific capacities of around 700mAhg−1 are observed between 1 and 0V for acid-treated cobalt–tin–carbon electrodes. The mechanism of the reaction with Li is explored by using ex situ 119Sn Mössbauer spectroscopy. In the charge process (Li-removing) two phases are segregated from the original lithiated phase. [Copyright &y& Elsevier]

Abstract: Some tri- and diorganotin(IV) compounds of the general formula, R n SnL4−n (where n =2, R=Me, n-Bu and Ph; n =3, R=Me, n-Bu, n-Pr and Ph; HL=5-amino-3H-1,3,4-thiadiazole-2-thione) have been synthesized by the reaction of RnSnCl4−n (where n =2 or 3, R=Me, n-Bu, n-Pr and Ph) and the sodium salt of the ligand. Oct2SnL2 was obtained by the reaction of Oct2SnO with HL in a 1:2 molar ratio under azeotropic removal of water. The bonding and coordination behavior in these derivatives are discussed on the basis of IR, Far-IR, multinuclear (1H, 13C and 119Sn) NMR and 119Sn Mössbauer spectroscopic studies. These investigations suggest that in all the compounds the ligand acts as monoanionic bidentate coordinating through ring N(3) and exocyclic S. Thermal studies of five compounds, viz., Ph3SnL, Me2SnL2, n-Bu2SnL2, Oct2SnL2 and Ph2SnL2 have been carried out in the temperature range 25–1000°C using TG, DTG and DTA techniques under an atmosphere of dry nitrogen. [Copyright &y& Elsevier]

Abstract: Some organotin(IV) triazolates of general formula R n Sn(L)4− n (where R=Me, n-Bu and Ph for n =2; R=Me, n-Pr and n-Bu for n =3 and HL=3-amino-5-mercapto-1,2,4-triazole) have been synthesized by the reaction of R2SnCl2/R3SnCl with NaL in 1:2/1:1 molar ratio. Whereas, Oct2SnL2 has been synthesized azeotropically by the reaction of Oct2SnO and HL in 1:2 molar ratio. As good single crystals were not obtained, a large number of experimental techniques, viz. UV/Vis, IR, far-IR, multinuclear (1H, 13C and 119Sn) NMR and 119Sn Mössbauer spectroscopic studies, were used to accomplish a definitive characterization and determination of their most probable structures. In these compounds triazole acts as a monoanionic bidentate ligand, coordinating through Sexo and N(4). The IR and 119Sn Mössbauer spectroscopic studies allow us to deduce a highly distorted cis-trigonal-bipyramidal structure for R3SnL and a distorted skew trapezoidal-bipyramidal structure for R2SnL2, in the solid state. However, 1H, 13C and 119Sn NMR spectral studies revealed that weak bonding between tin and N(4) is further weakened in the solution leading to pseudo-tetrahedral/tetrahedral structure. [Copyright &y& Elsevier]

Abstract: New non-electrolytic triorganotin(IV) derivatives of dipeptides with general formulae R3Sn(HL), where R=Ph and HL=monoanion of glycylisoleucine (H2L-1), valylvaline (H2L-2), alanylvaline (H2L-3), leucylalanine (H2L-4), leucylleucine (H2L-5); R= n-Bu and HL=monoanion of glycylisoleucine (H2L-1) and leucylalanine (H2L-4); and R=Me and HL=monoanion of leucylalanine (H2L-4) have been synthesized and characterized on the basis of infrared, multinuclear 1H, 13C and 119Sn NMR and 119Sn Mössbauer spectroscopic studies. These investigations suggest that all the ligands in R3Sn(HL) act as monoanionic bidentates coordinating through the COO− and NH2 groups. The 119Sn Mössbauer studies, together with the NMR data, indicate that, for these polymeric derivatives, the polyhedron around tin in R3Sn(HL) is a trigonal-bipyramid with the three organic groups in the equatorial positions, while the axial positions are occupied by a carboxylic oxygen and the amino nitrogen atom from the adjacent molecule. The anti-inflammatory and cardiovascular activities and toxicity of all these compounds have been determined. Four of the complexes have also been screened against some of the chosen bacterial and fungal strains. The Ph3Sn(IV) compounds exhibit better anti-inflammatory and cardiovascular activities in comparison to the Me3Sn(IV) and n-Bu3Sn(IV) analogues. n-Bu3Sn(Gly-Ile) and Ph3Sn(Ala-Val) exhibit good antibacterial activity against all the chosen strains. [Copyright &y& Elsevier]

Abstract: New organotin(IV) complexes of the general formula R3Sn(L) (where R=Me, n-Bu and HL= l-proline; R=Me, Ph and HL= trans-hydroxy-l-proline and l-glutamine) and R2Sn(L)2 (where R= n-Bu, Ph and HL= l-proline; R=Ph, HL= trans-hydroxy-l-proline) have been synthesized by the reaction of R n SnCl4−n (where n =2 or 3) with sodium salt of the amino acid (HL). n-Bu2Sn(Pro)2 was synthesized by the reaction of n-Bu2SnO with l-proline under azeotropic removal of water. The bonding and coordination behavior in these complexes have been discussed on the basis of IR and 119Sn Mössbauer spectroscopic studies in the solid-state. Their coordination behavior in solution has been discussed with the help of multinuclear (1H, 13C and 119Sn) NMR spectral studies. The 119Sn Mössbauer and IR studies indicate that l-proline and trans-hydroxy-l-proline show similar coordination behavior towards organotin(IV) compounds. Pentacoordinate trigonal-bipyramidal and hexacoordinate octahedral structures, respectively, have been proposed for the tri- and diorganotin(IV) complexes of l-proline and trans-hydroxy-l-proline, in which the carboxylate group acts as bidentate group. l-Glutamine shows different coordination behavior towards organotin(IV) compounds, it acts as monoanionic bidentate ligand coordinating through carboxylate and amino group. The triorganotin(IV) complexes of l-glutamine have been proposed to have trigonal-bipyramidal environment around tin. The newly synthesized complexes have been tested for their antiinflammatory and cardiovascular activities. Their LD50 values are >1000mgkg−1. [Copyright &y& Elsevier]

Abstract: New diorganotin(IV) derivatives of the general formula R2Sn(Umb)2 (where R= n-Bu, n-Oct and Ph; Umb=umbelliferone anion) have been synthesized either by the reaction of R2SnO with umbelliferone under azeotropic removel of water or by the reaction of R2SnCl2 with sodium salt of umbelliferone. Further, the adducts of the general formula R2Sn(Umb)2·phen (where R= n-Bu and n-Oct; phen=1,10-phenanthroline) have also been synthesized by the interaction of R2Sn(Umb)2 with 1,10-phenanthroline. The bonding and coordination behavior in these derivatives are discussed on the basis of IR and 119Sn Mössbauer spectroscopic studies in solid state. Their coordination behavior in solution is discussed by the multinuclear (1H, 13C and 119Sn) NMR spectral studies. The Mössbauer and IR studies indicate that umbelliferone acts as a monoanionic bidentate ligand in R2Sn(Umb)2 coordinating through O(7) and O(1). A distorted octahedral geometry around tin has been proposed for R2Sn(Umb)2 as well as for R2Sn(Umb)2·phen in solid state. The newly synthesized derivatives have been tested for their anti-inflammatory and cardiovascular activities. The average LD50 value >1000mgkg−1 of these compounds indicates their safety margin. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]