Sn Complexes Research Articles

Oxidative halogenation of Sn(II)heteroaryl alkenolates: Formation of unusual trans-dihalo Sn(IV) complexes

A series of novel tin(IV)-heteroaryl alkenolates of the general formula [Sn(DMOTFP)2X2] (3–6, X=F, Cl, Br, I) were prepared by direct oxidative halogenation of the corresponding tin(II) derivative [SnII(DMOTFP)2] (2) and by cleavage of the carbon-tin bonds in diphenyltin dichloride [Ph2SnCl2] by (4,5-dimethyloxazolyl)-1,1,1-trifluoropropen-2-ol, (H-DMOTFP, 1) with a subsequent halide exchange reaction. The molecular structures elucidated in solution (multi-nuclear NMR spectroscopy) and by single crystal X-ray diffraction confirmed the sixfold coordination of the tin(IV) center with a distorted octahedral arrangement of ligands. An unusual centrosymmetric octahedral trans-dihalo configuration was found for the compounds [SnIV(DMOTFP)2X2] (X=Cl, Br, I), while the compound [Sn(DMOTFP)2F2] adopted a cis-dihalide configuration.

X-ray crystal structural and spectral studies of copper(II) and nickel(II) complexes of two asymmetric bis(thiosemicarbazone) ligands and the investigation of relationship between the N(4)-substituent and the electrochemical behavior

Asymmetric, potentially tetradentate ligands (H2L5, H2L6·2MeOH) are formed by subsequent condensation a 4-chlorophenyl thiosemicarbazide and 4-phenyl thiosemicarbazide for H2L5, 4-chlorophenyl thiosemicarbazide and 4-bromophenyl thiosemicarbazide for H2L6·2MeOH on dialdehyde (1). The mixed bis(thiosemicarbazones) and their copper(II) and nickel(II) complexes have been characterized with 1HNMR, IR, electronic spectra and X-ray crystallography. Both bis(thiosemicarbazones) form square-planar N2S2 complexes with nickel(II) and copper(II). Electrochemical investigation showed that all Cu(II) and Ni(II) complexes were reducible. The differences observed in the electrochemistry between symmetric and asymmetric complexes cannot be explained only by considering the electronic and steric effects of the substituents, it seems that the arrangement of energy levels of molecular orbitals has been changed in converting a symmetric into an asymmetric structure. The redox potential of asymmetric complexes has been shifted toward more positive potentials compared to the symmetric compounds.

A tetranuclear Sn(IV) 4-thiazolecarboxylate complex: synthesis, structure and catalytic behavior in the bulk ring-opening polymerization of glycolide

Abstract The reaction of 4-thiazolecarboxylic acid (Htzc) and dimethyltin(IV) dichloride with NaOH in mixed MeOH-H2O solvent led to the formation of a new Sn(IV) complex (Me2Sn)4(μ 3-O)2(tzc)4 (1). Its structure has been characterized by elemental analysis, IR spectroscopy and single crystal and powder X-ray diffraction. Single-crystal X-ray diffraction revealed that complex 1 crystallizes in the monoclinic P21/c space group with Z = 2 and has a tetranuclear structure with crystallographically imposed centrosymmetry. The as-synthesized complex 1 was found to be active toward the bulk solvent-free polymerization of glycolide, producing poly(glycolic acid) with a number-average molecular weight up to 55.5 kDa.

Sulfonated Schiff base Sn(IV) complexes as potential anticancer agents

Syntheses, crystal structures and biological activities of the diphenoxo-bridged diorgano dinuclear Sn(IV) compounds [Sn(Et)2(HL)(H2O)]2 (1) and [Sn(n-Bu)2(HL)(H2O)]2 (2) derived from the Schiff base 2-[(2,3-dihydroxyphenyl)methylideneamino]benzenesulfonic acid trihydrate (H3L·3H2O) are described. The monoprotonated form (HL2−) of the Schiff base behaves as O,O′-bidentate ligand, chelating the metal by the two phenoxo oxygen atoms. The hexacoordinated metal centres in 1 and 2 are bridged by a phenoxo oxygen and the remaining coordination positions are fulfilled by the other phenoxo oxygen, two organic groups (ethyl for 1 and n-butyl for 2) and a water molecule. A two dimensional zigzag sheet in 1 and three dimensional polymeric networks in H3L·3H2O and 2 are stabilized by a number of non-covalent, H-bonding and π⋯π stacking interactions. The DNA binding activities of these complexes have been studied by UV-vis and fluorescence spectroscopies. Their antiproliferative efficacies have been evaluated on A-549, HeLa and MDA-MB-231 cancer cell lines by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. IC50 values (1.35±0.23, 2.43±0.54 and 1.74±0.04μM for 2) are indicative of a substantial cytotoxicity of 2, mainly towards the A-549 lung cancer cell line. The greater antiproliferative efficacy of 2has further been studied by fluorescence activated cell sorting (FACS) and nuclear morphology by Hoechst/propidium iodide (PI) double staining method. The possible mode of the apoptotic pathway for 2has been substantiated by the reactive oxygen species (ROS) generation studies.

A New Ultrasound Assisted-Cloud Point Extraction Method for the Determination of Trace Levels of Tin and Antimony in Food and Beverages by Flame Atomic Absorption Spectrometry

In the current study, a new ultrasonic-assisted cloud-point extraction (UA-CPE) method for the preconcentration and determination of antimony and tin in the selected food and beverages was developed by flame atomic absorption spectrometry (FAAS). The method is based on the fact that formation of the stable ternary complexes of Sb(III) and Sn(IV) with 2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one (morin) in presence of cetyltrimethylammoniumbromide (CTAB) as both sensitivity improvement auxiliary ligand and counter ion, and then extraction into the micellar phase of poly(ethylene glycol-mono-p-nonylphenylether (PONPE 7.5) as extracting agent at pH 8.5. Under the optimized conditions, the calibration curves for Sb(III) and Sn(IV) were rectilinear with changing calibration sensitivities in ranges of 0.1–140 and 0.1–225 μg L−1, respectively. The limit of detection for both Sb(III) and Sn(IV) was 0.03 μg L−1 with sensitivity enhancement factor of 114.5 and 110.6, respectively. The precision as a relative standard deviation (RSD) for Sb(III) and Sn(IV) is in range of 2.3–5.2 and 2.6–5.4 %, respectively. The trueness of the method was verified by analysis of certified reference materials (CRMs). The method was successfully applied to determination of antimony and tin in the selected food and beverage matrices.

π-π stacking motifs in dialkylbis{5-[(E)-2-aryldiazen-1-yl]-2-hydroxybenzoato}tin(IV) complexes.

The diorganotin(IV) complexes of 5-[(E)-2-aryldiazen-1-yl]-2-hydroxybenzoic acid are of interest because of their structural diversity in the crystalline state and their interesting biological activity. The structures of dimethylbis{2-hydroxy-5-[(E)-2-(4-methylphenyl)diazen-1-yl]benzoato}tin(IV), [Sn(CH3)2(C14H11N2O3)2], and di-n-butylbis{2-hydroxy-5-[(E)-2-(4-methylphenyl)diazen-1-yl]benzoato}tin(IV) benzene hemisolvate, [Sn(C4H9)2(C14H11N2O3)2]·0.5C6H6, exhibit the usual skew-trapezoidal bipyramidal coordination geometry observed for related complexes of this class. Each structure has two independent molecules of the Sn(IV) complex in the asymmetric unit. In the dimethyltin structure, intermolecular O-H...O hydrogen bonds and a very weak Sn...O interaction link the independent molecules into dimers. The planar carboxylate ligands lend themselves to π-π stacking interactions and the diversity of supramolecular structural motifs formed by these interactions has been examined in detail for these two structures and four closely related analogues. While there are some recurring basic motifs amongst the observed stacking arrangements, such as dimers and step-like chains, variations through longitudinal slipping and inversion of the direction of the overlay add complexity. The π-π stacking motifs in the two title complexes are combinations of some of those observed in the other structures and are the most complex of the structures examined.

Spectroscopic Characterization of Stability and Interaction of Pt-Sn Complexes with Different Capping Agents

Colloidal metal nanoparticles are of great interest because of their use as catalysts, photocatalyst, adsorbent and sensors and because of their application in optical, electronic and magnetic devices. Capping agents are widely used in the synthesis of colloidal nanocrystals, and their roles are generally as stabilizers. A heat-treatment method for the preparation of well-stable Pt-Sn complex is demonstrated using different capping agents such as mercaptosuccinic acid (MSA), mono ethylene glycol, polyacrylic acid, and poly (vinyl pyrrolidone) etc. The stability and interaction of Pt- Sn complexes with different capping agents were characterized by UV–via absorption spectroscopy. Pt-Sn bimetallic nanoparticles have been prepared and characterized by UV–via spectroscopy.

Structural insights into the coordination chemistry and reactivity of a 3,3′-bis-imine-2,2′-bipyridine ligand

The coordination chemistry of the bis-salicyl-appended Schiff-base ligand L8 with Lewis acidic metal ions affords the mononuclear complex [Sn(L9)Cl4] (1) and two paramagnetic dimers [Cu(L9)(sal)]2(ClO4)2, (2) and [Mn(L9)Cl2(EtOH)]2] (3). The X-ray crystal structures of 1–3 reveal a propensity for L8 to undergo metal catalyzed hydrolysis and cyclization to the diazepine ligand L9. Theoretical calculations on L8 and a model Sn(IV) complex reveal that coordination to a metal ion weakens the imine bonds, rendering them more susceptible to hydrolysis reactions and/or attack by nucleophiles. In contrast, reaction of L8 with FeCl3 in the presence of base affords the partial hydrolysis product [Fe(L10)2]Cl·CH3CN (4). Tuning the reaction conditions via the addition of a second base slows down the hydrolysis of the ligand sufficiently to afford a few crystals of the μ2-oxo diferric complex (μ-O)[Fe(L8)]2·2CH3CN (5) in which intact L8 coordinates to the Fe(III) in a bis-bidentate manner through a deprotonated salicyl oxygen and a bis-imine nitrogen lone pair, with the nitrogen atoms of its 2,2′-bipyridine remaining uncoordinated.

Solvation structure around the Li(+) ion in succinonitrile-lithium salt plastic crystalline electrolytes.

Herein, we discuss the study of solvation dynamics of lithium-succinonitrile (SN) plastic crystalline electrolytes by ultrafast vibrational spectroscopy. The infrared absorption spectra indicated that the CN stretch of the Li(+) bound and unbound succinonitrile molecules in a same solution have distinct vibrational frequencies (2276 cm(-1)vs. 2253 cm(-1)). The frequency difference allowed us to measure the rotation decay times of solvent molecules bound and unbound to Li(+) ion. The Li(+) coordination number of the Li(+)-SN complex was found to be 2 in the plastic crystal phase (22 °C) and 2.5-3 in the liquid phase (80 °C), which is independent of the concentration (from 0.05 mol kg(-1) to 2 mol kg(-1)). The solvation structures along with DFT calculations of the Li(+)-SN complex have been discussed. In addition, the dissociation percentage of lithium salt was also determined. In 0.5 mol kg(-1) LiBF4-SN solutions at 80 °C, 60% ± 10% of the salt dissociates into Li(+), which is bound by 2 or 3 solvent molecules. In the 0.5 mol kg(-1) LiClO4-SN solutions at 80 °C, the salt dissociation ratio can be up to 90% ± 10%.

Synthesis of [Pt(SnBu(t)3)(IBu(t))(μ-H)]2, a Coordinatively Unsaturated Dinuclear Compound which Fragments upon Addition of Small Molecules to Form Mononuclear Pt-Sn Complexes.

The reaction of Pt(COD)2 with one equivalent of tri-tert-butylstannane, Bu(t)3SnH, at room temperature yields Pt(SnBu(t)3)(COD)(H)(3) in quantitative yield. In the presence of excess Bu(t)3SnH, the reaction goes further, yielding the dinuclear bridging stannylene complex [Pt(SnBu(t)3)(μ-SnBu(t)2)(H)2]2 (4). The dinuclear complex 4 reacts rapidly and reversibly with CO to furnish [Pt(SnBu(t)3)(μ-SnBu(t)2)(CO)(H)2]2 (5). Complex 3 reacts with N,N'-di-tert-butylimidazol-2-ylidene, IBu(t), at room temperature to give the dinuclear bridging hydride complex [Pt(SnBu(t)3)(IBu(t))(μ-H)]2 (6). Complex 6 reacts with CO, C2H4, and H2 to give the corresponding mononuclear Pt complexes Pt(SnBu(t)3)(IBu(t))(CO)(H)(7), Pt(SnBu(t)3)(IBu(t))(C2H4)(H)(8), and Pt(SnBu(t)3)(IBu(t))(H)3 (9), respectively. The reaction of IBu(t) with the complex Pt(SnBu(t)3)2(CO)2 (10) yielded an abnormal Pt-carbene complex Pt(SnBu(t)3)2(aIBu(t))(CO) (11). DFT computational studies of the dimeric complexes [Pt(SnR3)(NHC)(μ-H)]2, the potentially more reactive monomeric complexes Pt(SnR3)(NHC)(H) and the trihydride species Pt(SnBu(t)3)(IBu(t))(H)3 have been performed, for NHC = IMe and R = Me and for NHC = IBu(t) and R = Bu(t). The structures of complexes 3-8 and 11 have been determined by X-ray crystallography and are reported.

Metal Organic Structure Built from Binuclear Sn(IV) Complex: Synthesis, Characterization, and X-Ray Structural Studies

A 3D metal organic structure of a p-block metal ion, Sn(IV) atom, formulated as [Sn(pydc)(HOC2H5)(CH3)2]2, was synthesized and characterized. This complex is binuclear with two bridging oxygen atoms of carboxylate groups. Each of the two Sn(IV) atoms is also coordinated by the chelate (pydc)2− ligand and two terminal CH3 groups as well as by one terminal HOC2H5 group. Based upon the molecular structure analysis, the coordination environment around each Sn(IV) atom is distorted pentagonal bipyramid. The hydrogen bonding between carbonyl and ethoxy groups of two neighboring neutral complexes produce the Zig-Zag arrangements.

Synthesis and biological activity of trinuclear seven-coordinated tin(IV) complexes derived from tridentate ligands and trimesic acid

The synthesis of trinuclear Sn(IV) complexes 5a–h – prepared in a one-pot reaction of 2-amino-4-R-phenol (R=H, Me, Cl, NO2), 2-pyridine-carboxaldehyde, 1,3,5-benzenetricarboxylic acid (trimesic acid, H3BTC), and dibutyl and dioctyltin oxides – is described. These compounds were characterized by elemental analysis, mass spectrometry, IR, and multinuclear NMR spectroscopy. The structures of 5a and 5b were also determined by single-crystal X-ray analysis. The trinuclear tin system is formed by bridges through the carboxylate moieties. The metal centers are seven-coordinate and the coordination polyhedron of tin can be depicted as distorted pentagonal-bipyramidal (PBP), where the equatorial plane consists of three oxygens and two nitrogens and the organic groups occupy the axial positions. The work presented here combines the useful properties of Schiff bases and H3BTC ligands in the formation of organotin(IV) complexes, and investigates the likely antioxidant (DPPH and TBARS) and anti-inflammatory activity (TPA) of the new substances.

Improved stability of nano-Sn electrode with high-quality nano-SEI formation for lithium ion battery

Sn materials offer high theoretical capacities in lithium ion batteries, but they must have good cycling stability and high rate-capability in order to be commercialized. Complex and costly material treatments of Sn have been effective in reducing capacity fade, but conventionally produced bare Sn is desired for reducing cost. One simple method is to form a high-quality solid electrolyte interphase (SEI) on Sn particles with low resistance and high passivation. Fluoroethylene carbonate (FEC) added to the electrolyte forms a protective and less-resistant SEI on Sn particles during the in-situ electrochemical SEI formation cycle. FEC is a good oxidizing agent that removes highly oxidized carbon compounds and makes a SEI thinner during an oxidation process (delithiation) of SEI formation cycle. The high-quality SEI greatly improves the rate-capability and capacity of nano-sized bare Sn electrodes without any treatments: minimal capacity fade (0.014% cycle−1) at 320mAhg−1 (1.3C) for 150 cycles. The mitigating effect of FEC on capacity fade is not seen with electrodes fabricated from micro-scale (0.1~0.2μm) Sn. The long lithium-ion diffusion path makes these micro-sized materials susceptible to decrepitation during repeated volume changes.

Near-infrared luminescent Sn(IV) complexes of N-confused tetraphenylporphyrin: Effect of axial anion coordination

Novel tin(IV) halo complexes of an N-confused tetraphenylporphyrin with different axial ligands have been synthesized and characterized by various spectroscopic methods including X-ray crystallographic analysis. The molecular structures of the dichloro and dibromo derivatives possess perfect octahedral geometries, which are nearly comparable to the corresponding regular porphyrin complexes. In contrast, the iodide/triiodide complex obtained by a same reaction manner, demonstrated that the tin(IV) cation is slightly displaced towards axially coordinated iodide anion, giving rise to the different electronic structure due to the tautomeric form of N-confused porphyrin ligand. These structural differences reflected to the distinct photophysical and electrochemical properties. The Sn(IV) complexes are near IR luminescent, however the unsymmetrical axial coordination of iodide and triiodide anions in the tin(IV) N-confused porphyrin complex allows, in particular, the longer emission lifetimes and a smaller singlet-triplet energy gap, which were investigated by steady-state and time-resolved spectroscopies as well as theoretical calculations.

1,2‐Dithiooxalato‐Bridged Heterobimetallic Complexes as Single‐Source Precursors for Ternary Metal Sulfide Semiconductors

AbstractThe new 1,2‐dithiooxalato‐bridged bimetallic Cu–Ga, Cu–In, and Cu–Sn complexes [{(Ph3P)2Cu(μ‐S2C2O2)}3Ga] (1), [{(Ph3P)2Cu(μ‐S2C2O2)}3In] (2), [(Ph3P)2Cu(μ‐S2C2O2)In(S2CNEt2)2] (3), and [{(Ph3P)2Cu(μ‐S2C2O2)}2Sn(S2C2O2)] (4) were prepared and spectroscopically fully characterized. The crystal structures of 2–4 are presented. Complexes 3 and 4 are potential molecular single‐source precursors (SSP) for the ternary semiconductors CuInS2 and Cu2SnS3, respectively, which can be manipulated under ambient conditions. Indeed, a study of the thermal degradation of 3 and 4 revealed that 3 affords pure nanoscaled CuInS2 (mean diameter ca. 2 nm) when the decomposition is carried out in an oleylamine solution by using a hot‐injection or arrested‐precipitation technique at temperatures well below 250 °C. In contrast, 4 decomposes under the same reaction conditions in an ambiguous manner and forms mixed binary chalcogenide phases. This can be explained by a subtle influence of the relative stability of possible SnII and SnIV intermediates in the case of SSP [{(Ph3P)2Cu(μ‐S2C2O2)}2Sn(S2C2O2)] (4).

Coordination Nature of 4-Mercaptoaniline to Sn(II) Ion: Formation of a One Dimensional Coordination Polymer and Its Decomposition to a Mono Nuclear Sn(IV) Complex

The coordination of the bifunctional ligand 4-mercaptoaniline with aqueo us tin(II) metal ion was studied. A coordination polymer was synthesized when an aqueous solution of SnCl2 was treated with 4-MA. The crystalline material is stable under atmospheric conditions retaining its oxidation state. However, when submerged in a solution saturated with oxygen, the compound oxidizes to a mononuclear tin(IV) complex. Both the compounds were characterized by single crystal X-ray diffraction studies. Although the structure of the tin(IV) complex was previously reported, crystal structure of this compound was redetermined.

Synthesis, characterization and antimicrobial activity of N,N-bis(hydroxymethyl)-N-[(2-mercaptoacetoxy)methyl]alkyl ammonium bromide surfactant and their Co(II), Zn(II) and Sn(II) complexes

Two-membered cationic surfactants namely: N,N-bis(hydroxymethyl)-N-[(2-mercaptoacetoxy)methyl)dodecane ammonium bromide (C12Q) and N,N-bis(hydroxymethyl)-N-[(2-mercaptoacetoxy)methyl]hexadecane ammonium bromide (C16Q) and their cobalt, tin and zinc complexes (C12QCo, C12QSn, C12QZn, C16QCo, C16QSn and C16QZn) were synthesized. The chemical structures of the synthesized compounds were confirmed using different spectroscopy tools. The surface activities of the synthesized surfactants were influenced by their chemical structures and the type of the transition metals. The synthesized cationic surfactants and their metal complexes were evaluated as biocides against Gram- positive bacteria (Bacillus subtilis and Micrococcus luteus), Gram-negative bacteria (Bordetella pertussis and Escherichia coli) and fungi (Candida albicans and Aspergillus niger), while the sulfate-reducing bacteria were tested against Desulfomonas pigra. The biological activity results showed that the cationic surfactants exhibit moderate to high efficiency against the tested microorganisms. The antimicrobial activity was strongly increased by complexation of these cationic surfactants with Co(II), Sn(II) and Zn(II) ions. The antimicrobial activity of the synthesized compounds against sulfate-reducing bacteria showed promising results in the field of biocides application.

Tetrahedral Sn-silsesquioxane: synthesis, characterization and catalysis.

A tetrahedral stannasilsesquioxane complex was synthesized as a racemic mixture using Sn(O(i)Pr)4 and silsesquioxanediol, and its structure was confirmed with X-ray crystallography, NMR, and EXAFS. The complex was a Lewis acid, and both anti and syn-binding with Lewis bases were possible with the formation of octahedral Sn complexes. It was also a Lewis acid catalyst active for epoxide ring opening and hydride transfer.

Influence of different alkyl and carboxylate substituents on Sn(IV) organometallic catalysts during fatty acid methyl ester production

Sn(IV) complexes (dimethyltin dineodecanoate (1), dibutyltin dineodecanoate (2), dioctyltin dineodecanoate (3), dimethyltin diundec-10-enoate (4), dibutyltin diundec-10-enoate (5), tributyltin undec-10-enoate (6) and tributyltin undecanoate (7)) were tested as catalysts for transesterification or esterification in the presence of methanol, in order to investigate the effect of the substituents coordinated to the metal center. All complexes were active at relative high reaction temperatures, and their reactivity can be associated with the steric effects induced by the substituents (alkyls and carboxylates) at the metal center.

An Inexpensive and Sensitive Method for Speciative Determination of Sn(IV), Sn(II), and Total Sn as Sn(IV) in Selected Beverages by Micellar Improved Spectrophotometry

In the present study, an inexpensive, selective, and micellar sensitive spectrophotometric method for Sn(IV) was developed at 537 nm. The method is based on the formation of ternary complex of Sn(IV) with tartaric acid and Celestine blue in the presence of sodium dodecyl sulfate (SDS) and polyethylene glycol tert-octylphenyl ether (Triton X-114) at pH 3.5. The analytical variables affecting cloud point extraction (CPE) efficiency were optimized in detail. Under the optimized conditions, the calibration graph was linear in the range of 4–350 μg L−1 with changing dye concentration for Sn(IV) ions. The limits of detection and quantification of the method were found to be 1.3 and 4.3 μg L−1 for Sn(IV), respectively. Relative standard deviation (RSDs) for five replicate determinations at 20 and 100 μg L−1 concentration levels were 4.4 and 1.5 %, respectively. Recovery values of spiked samples were obtained in range of 97.7–103.3 %. Matrix effect on the extraction efficiency were also investigated. The method was successfully applied to the determination of Sn(II), Sn(IV) and total Sn in some selected beverages before and after pretreatment with H2O2 in acidic media, prior to analysis. Validity of the method was controlled through the analysis of two certified reference materials. It has been observed that the results are highly compatible with the certified values.