Tin Cation Research Articles

Synthesis, crystal structure, in vitro anticholinesterase activity, molecular docking and DFT investigation of three 1,10-phenanthroline-tin(IV) complexes

This work describes the synthesis, the crystal structure and the properties of three tin complexes derivatives of 1,10-phenanthroline, namely C24H19N3SnCl2 (C1), C24H20N4SnCl2 (C2) and C27H22N4SnCl2 (C3). Their structures were elucidated by X-ray diffraction, IR and NMR (1H &13C). The in vitro anticholinesterase activity was investigated and compared to docking findings. The obtained results showed that the C2 complex presents the closest IC50 value (10.99±0.34 μM) to that of galantamine (4.14±0.07 μM) and corroborated by the docking results, where C2 and C1 showed a score of 54.08, 51.32 for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity, respectively. The optimized structures obtained by density functional theory (DFT) gave comparable geometrical parameters around the tin(IV) cation of hexacoordination environment. The computed HOMO-LUMO gaps are large predicting stable compounds. The natural population analysis attributes negative charges of chlorine, carbon and nitrogen atoms directly bound to the tin(IV) cation. However, the natural charges of tin(IV) of +1.63 in both C1 and C2 compounds are lower than +1.74 calculated for C3, suggesting different electron transfers. The FMOs localizations and Fukui functions predict that C1 and C2 behave differently from C3 with regard to the reactivity towards protein targets, in agreement with the experimental data and the molecular docking results.

Investigating solid solutions: Geometric transformations triggered by germanium incorporation in Cu2ZnGexSn1−xS4

Through experimental exploration, diverse phases—tetragonal and orthorhombic—have been observed within the Cu2ZnGexSn1−xS4 region (0 ≤ x ≤ 1), hinting at potential miscibility gaps. To complement these findings, our computational investigation, employing density functional theory (DFT), delves into the Ge substitution-induced phase transition in Cu2ZnGexSn1−xS4. Contrary to a single-phase behavior, our FP-LAPW at zero temperature results reveal a compelling shift from stannite (Sn-rich) to Wurtzite-Stannite (Ge-rich) at xGe ≈ 80%. Negative enthalpy of formation values indicates the inherent stability of these structures. The calculations reveal an estimated 8.884 meV per atom difference in enthalpies of formation between the Stannite and Wurtzite-Stannite phases for Cu2ZnSnS4. For Cu2ZnGeS4, the Wurtzite-Stannite structure emerges as the most stable, closely trailed by the Stannite structure, with enthalpies of formation at − 4.833 eV·atom−1 and − 4.804 eV·atom−1, respectively. Furthermore, our quasi-harmonic Debye model facilitates the analysis of phase transitions triggered by the introduction of germanium. This is achieved by calculating the Gibbs energy, which remains unaffected by variations in temperature and pressure. As the tin cation is replaced by the smaller germanium cation, there is an observable decrease in the cell parameters. The corresponding reduction in cell volume adheres to the principles of Vegard's Law. Exploring the behavior of these materials in diverse conditions can significantly contribute to enhancing the performance and stability of devices built upon Cu2ZnGexSn1−xS4.

Utilization of a Tris(carbene)borate Ligand for Umpolung Reactivity of a Nucleophilic Tin(II) Cation Salt.

We show that a tris(carbene)borate (TCB) ligand, namely [PhB(tBuIm)3]- ([PhB(tBuIm)3]- = phenyltris(3-tert-butylimidazol-2-ylidene)borato), is capable of stabilizing an unprecedented nucleophilic Sn(II) cation salt. Unlike known Sn(II) cations, the strong electron-donating ability of [PhB(tBuIm)3]- makes the cationic tin atom electron-rich, σ-donating yet slightly π-accepting, which allows for the ensuing facile oxidation with o-chloranil and S8 as well as coordination with coinage metals. The former oxidations give the Sn(IV) cation salts, while the latter reactions produce the metal complexes. The electronic structures of these species are thoroughly probed by quantum chemical computations. These results uncover an added role for TCB ligands in isolating unprecedented p-block species.

Sulfur vacancy in SnS2 nanoflake adjusted by precursor and improved photocatalytic performance

SnS2 with nanoflake-based microstructure and different concentrations of sulfur vacancy (SV) has been synthesized. The valence state of tin cation in the precursors is found to be closely related to the SV concentration in SnS2 nanoflake. SnS2 nanoflake with unsaturated tin cation in tin salt precursor (SnCl2·2H2O) favors to create SV. Sufficient SV is found to bring about a number of advantages such as smaller energy band gap, larger electrochemical active surface Area (ECSA), improved light absorption and separation efficiency of photogenerated charge carriers, which results in superior photocatalytic activities for degradation of RhB and CO2. SnS2 with more sulfur vacancies exhibits better photocatalytic activity for RhB degradation with a degradation rate 1.02×10−2min−1 and for CO2 reduction with an average CO production rate 2.44μmol∙g−1∙h−1. Above results not only reveal the importance of defect engineering, but also provide valuable guide to develop effective metal-sulfide photocatalysts for organic pollutant degradation and CO2 reduction.

On the effective ionic radii for the tin(II) cation

Based on the bond valence (s)–bond length (d) correlation curve accurately approximated for the Sn2+/F− ion pair using the equation s = exp[(r0 – d)/b] (where the optimized bond valence parameters are r0 = 1.761 Å and b = 0.52 Å), a set of effective ionic radii corresponding to different coordination numbers (CNs) and compatible with the Shannon radii system were derived for the Sn2+ cation as: 0.66 Å (CN = III), 0.81 Å (CN = IV), 1.02 Å (CN = VI), 1.17 Å (CN = VIII), and 1.38 Å (CN = XII).

Photocatalytic Hydrogen Production by the Sensitization of Sn(IV)-Porphyrin Embedded in a Nafion Matrix Coated on TiO2.

Efficient utilization of visible light for photocatalytic hydrogen production is one of the most important issues to address. This report describes a facile approach to immobilize visible-light sensitizers on TiO2 surfaces. To effectively utilize the sensitization of Sn(IV) porphyrin species for photocatalytic hydrogen production, perfluorosulfonate polymer (Nafion) matrix coated-TiO2 was fabricated. Nafion coated-TiO2 readily adsorbed trans-diaqua[meso-tetrakis(4-pyridinium)porphyrinato]tin(IV) cation [(TPyHP)Sn(OH2)2]6+ via an ion-exchange process. The uptake of [(TPyHP)Sn(OH2)2]6+ in an aqueous solution completed within 30 min, as determined by UV-vis spectroscopy. The existence of Sn(IV) porphyrin species embedded in the Nafion matrix coated on TiO2 was confirmed by zeta potential measurements, UV-vis absorption spectroscopy, TEM combined with energy dispersive X-ray spectroscopy, and thermogravimetric analysis. Sn(IV)-porphyrin cationic species embedded in the Nafion matrix were successfully used as visible-light sensitizer for photochemical hydrogen generation. This photocatalytic system performed 45% better than the uncoated TiO2 system. In addition, the performance at pH 7 was superior to that at pH 3 or 9. This work revealed that Nafion matrix coated-TiO2 can efficiently produce hydrogen with a consistent performance by utilizing a freshly supplied cationic Sn(IV)-porphyrin sensitizer in a neutral solution.

Tin Carboxylate Complexes of Natural Bacteriochlorin for Combined Photodynamic and Chemotherapy of Cancer è.

Photodynamic therapy (PDT) is currently one of the most promising methods of cancer treatment. However, this method has some limitations, including a small depth of penetration into biological tissues, the low selectivity of accumulation, and hypoxia of the tumor tissues. These disadvantages can be overcome by combining PDT with other methods of treatment, such as radiation therapy, neutron capture therapy, chemotherapy, etc. In this work, potential drugs were obtained for the first time, the molecules of which contain both photodynamic and chemotherapeutic pharmacophores. A derivative of natural bacteriochlorophyll a with a tin IV complex, which has chemotherapeutic activity, acts as an agent for PDT. This work presents an original method for obtaining agents of combined action, the structure of which is confirmed by various physicochemical methods of analysis. The method of molecular modeling was used to investigate the binding of the proposed drugs to DNA. In vitro biological tests were carried out on several lines of tumor cells: Hela, A549, S37, MCF7, and PC-3. It was shown that the proposed conjugates of binary action for some cell lines had a dark cytotoxicity that was significantly higher (8–10 times) than the corresponding metal complexes of amino acids, which was explained by the targeted chemotherapeutic action of the tin (IV) complex due to chlorin. The greatest increase in efficiency relative to the initial dipropoxy-BPI was found for the conjugate with lysine as a chelator of the tin cation relative to cell lines, with the following results: S-37 increased 3-fold, MCF-7 3-fold, and Hela 2.4-fold. The intracellular distribution of the obtained agents was also studied by confocal microscopy and showed a diffuse granular distribution with predominant accumulation in the near nuclear region.

FTIR, Weight, and Surface Morphology of Poly(vinyl chloride) Doped with Tin Complexes Containing Aromatic and Heterocyclic Moieties.

Poly(vinyl chloride) (PVC) is an important synthetic plastic that is produced in large quantities (millions of tons) annually. Additives to PVC are necessary to allow its use in many applications, particularly in harsh conditions. In regard to this, investigation of the synthesis of trimethoprim–tin complexes and their use as PVC additives is reported. Trimethoprim–tin complexes were obtained from the reaction of trimethoprim and tin chlorides using simple procedures. Trimethoprim–tin complexes (0.5% by weight) were added to PVC to produce homogenous mixtures and thin films were made. The effect of ultraviolet irradiation on the surface and properties of the PVC films was investigated. The level of both photodecomposition and photo-oxidation of PVC films containing trimethoprim–tin complexes was observed to be lower than for the blank film. The effectiveness of tin complexes as PVC photostabilizers reflects the aromaticity of the additives. The complex containing three phenyl groups attached to the tin cation showed the most stabilizing effect on PVC. The complex containing two phenyl groups was next, with the one containing butyl substituents resulting in the least stabilization of PVC. A number of mechanisms have been proposed to explain the role of the synthesized complexes in PVC photostabilization.

Water soluble porphyrin-fluorescein triads: Design, DFT calculation and pH-change-triggered fluorescence response

This paper reports the results of the synthesis and identification of water soluble trans-diaxial complexes of Sn(IV)-5,10,15,20-tetra-(4-sulfophenyl)porphyrin with fluorescein, in which the organic ligands are bound to the tin cation of the tetrapyrrolic macrocycle via a carboxyl (triad I) or a hydroxyl (triad II) group. The structures of triads (I, II) were confirmed by the methods of one- and two-dimensional NMR and quantum-chemical modeling. A spectrophotometric method was used to study the spectral, acidic and fluorescence properties of the synthesized compounds. The paper also discusses the possible mechanisms of protolytic and tautomeric equilibria in the processes involving fluorescein ligands in the axial complexes with hydrophilic Sn(IV)porphyrin. It is found that the fractional distribution of the triads with the lactone, quinoid, and zwitterionic forms of fluorescein axial ligands depends on the medium acidity, exhibiting high pH sensitivity in the ranges where this substance and its derivatives in the free state do not exhibit fluorescence. As a result, the ability of the porphyrin-fluorescein triads to determine water acidity can be used to develop an effective method of detecting pH-dependent biological processes and environmental pollution. This method will facilitate the production of new fluorescent sensors for biomedical purposes (drug delivery triggered by pH changes or oxygen distribution in tissues) and engineering applications (wastewater detection).

Chemically-Engineered Host Materials Enabling Safe Sodium Metal Anodes

As an anode material, sodium (Na) metal is the most promising alternative for lithium for the next‐generation energy storage systems. Nevertheless, its practical implementation is impeded by the huge volume change and severe Na metal dendrite growth during electrochemical stripping/plating. Herein, the employment of chemically-engineered porous copper (Cu) and titanium carbide (Ti3C2) MXene as stable host for metallic Na anode is presented. By treating the commercial Cu foam through a facile and cost‐effective method, a composite matrix consists of cylindrical core–shell skeleton is achieved, facilitating uniform impregnation and confinement of Na within the matrix pores promoted by the chemical interaction between Na and the matrix. While by treating Ti3C2 via a facile cetyltrimethylammonium bromide prepillaring followed by subsequent Tin cation (Sn2+) pillaring, a Sn2+ pillared Ti3C2 MXene matrix is obtained, guiding the Na nucleation/growth within the matrix interlayer space and contributing to uniform Na deposition facilitated by the chemical interaction between Na and Sn-based nanocomplexes encapsulated within the MXene layers. The unique characteristic of the chemically-engineered host materials can well accommodate hostless Na+, suppressing the volume change and mossy/dendritic Na growth during cycling. A stable Na cycling behavior is demonstrated in carbonate electrolyte without any additives at a high capacity up to 3 mAh/cm2 with a current density up to 2 mA/cm2. While in ether electrolyte, a stable Na performance at a high capacity up to 5 mAh/cm2 along with a high current density up to 10 mA/cm2 is achieved. Furthermore, electrochemical measurements of a full cell made of the Na composite matrix anodes clearly reveal the superior performance over that using bare Na metal. We believe that our approach provides facile approaches to the fabrication of stable Na metal anodes for high‐energy Na‐based batteries, and could be a viable strategy for other metallic anode systems.[1,2] Reference： [1] C.Wang, H. Wang, E. Matios, X. Hu, W. Li, Adv. Funct. Mater, 2018, 28, 1802282. [2] J. Luo, † C. Wang, † H. Wang, X. Hu, E. Matios, X. Lu, W. Zhang, X. Tao, W. Li, Adv. Funct. Mater, 2018, 1805946. Figure 1

Enhancing the crystallinity and perfecting the orientation of formamidinium tin iodide for highly efficient Sn-based perovskite solar cells

Low power conversion efficiency (PCE) and poor reproducibility are among the main challenges for tin-based perovskite solar cells (HPSCs). The facile formation of tin vacancies and oxidation of the divalent tin cation during the thin film fabrication process are among the causes of these problems, because the tin perovskite layer then becomes p-doped, resulting in significant trap-assisted recombination losses in devices. In this paper, we demonstrate that increasing the crystallinity of the tin perovskite film is an effective way to address the open issues with Sn-based perovskites. We succeed in improving the crystallinity of the 3D formamidinium tin iodide (FASnI3) grains, increasing their size, and perfecting their orientation in the out-of-plane direction by incorporating ethylammonium iodide (EAI) into a 2D/3D tin perovskite film (where 2D is PEA2FASn2I7, PEA = phenylethylammonium). This leads to a decrease of traps and background charge carrier density, and therefore to decreased charge recombination losses in EAx2D/3D based devices, as compared not only to devices based on FASnI3 but also to those based on 2D/3D mixtures. As a consequence, devices using a perovskite layer with composition EA0.082D/3D exhibit much higher PCE (8.4%) and better reproducibility compared to devices based on mixed 2D/3D perovskites (7.7%) and 3D perovskite (4.7%).

Ionic assembled hybrid nanoparticle consisting of tin(IV) porphyrin cations and polyoxomolybdate anions, and photocatalytic hydrogen production by its visible light sensitization

A new porphyrin–polyoxometalate hybrid nanoparticle was synthesized by the ionic assembly between trans-diaquo[5,10,15,20-tetrakis(4-pyridinium)porphyrinato]tin(IV) cation (SnP) and phosphomolybdate anion (POMo) in aqueous solution. UV–vis spectroscopic investigation on SnP–POMo nanoparticles supports that J-aggregation mainly occurs in SnP–POMo rather than H-aggregation. The influences of temperature or pH to the formation of SnP–POMo nanoparticle were examined. DLS measurements revealed that the average hydrodynamic diameter of SnP–POMo in water is ca. 245nm with narrow distributions in size. The photocatalytic hydrogen production from water by the SnP–POMo sensitization exhibited higher activity than that of SnP under visible light irradiation.

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.

Formation of an imino-stabilized cyclic tin(II) cation from an amino(imino)stannylene.

The novel amino(imino)stannylene 1 was prepared by conversion of HNIPr (NIPr = bis(2,6-diisopropylphenyl)imidazolin-2-imino) with one equivalent of Lappert's tin reagent (Sn[N(SiMe3)2]2). Treatment of 1 with DMAP (4-dimethylaminopyridine) yields its Lewis acid-base adduct 2. The reaction of 1 with one equivalent of trimethylsilyl azide results in replacement of the amino group at the tin center by an N3 substituent with concomitant elimination of N(SiMe3)3 to afford dimeric [N3SnNIPr]2 (3). Remarkably, the reaction of 1 with B(C6F5)3 produces the novel tin(II) monocation 4(+)[MeB(C6F5)3](-) comprising a four-membered stannacycle through methyl-abstraction from the trimethylsilyl group.

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.

Inside Back Cover: On the Catalysis of the Cycloisomerization of 1,6‐Dienes with Tin(IV) Salts: The Important Role of a Water Molecule (ChemCatChem 2/2014)

Water gets the cat out of the tin The cover picture shows a key transition state involved in the cyclisation of 1,6-dienes catalysed by a tin catalyst. In the computations and experiments presented in their Full Paper on p. 500 ff., P. Nava et al. explain how a water molecule is necessary for reaction completion and catalyst regeneration. It is shown that the tin cation does not directly participate in the reaction but sits aside on an ester lone pair of the diene. A water molecule, strongly acidic owing to its coordination to the metal, is positioned perfectly over the substrate and transfers protons at the right places along the cyclisation process (orange dots). The catalysis and its diastereoselectivity are determined completely by this coordinated water molecule.

On the Catalysis of the Cycloisomerization of 1,6‐Dienes with Tin(IV) Salts: The Important Role of a Water Molecule

AbstractA diene cycloisomerisation reaction catalysed by tin(IV) triflimidate is studied by using DFT computations. It is proposed that the mechanism does not involve the direct addition of the tin(IV) cation to a double bond because the catalyst regeneration step would be energetically unfeasible. We show that a water molecule may play a decisive role to enable the smooth completion of the catalytic cycle. The proposed active catalyst is thus a hydrated triflimidate salt. The hydrolysis and hydration energies are computed for three ligands of SnL4, L=triflate (OTf), triflimidate (NTf2) and a chlorosulfonate model (OSO2Cl). The diastereoselectivity observed in the cycloisomerisation is discussed in light of the transition‐state geometries. The hypothesis of hidden Brønsted acid catalysis is discussed and ruled out on the basis of new experimental results.

Synthetic and Mechanistic Aspects of the Immortal Ring‐Opening Polymerization of Lactide and Trimethylene Carbonate with New Homo‐ and Heteroleptic Tin(II)‐Phenolate Catalysts

Several new heteroleptic Sn(II) complexes supported by amino-ether phenolate ligands [Sn{LO(n)}(Nu)] (LO(1)=2-[(1,4,7,10-tetraoxa-13-azacyclopentadecan-13-yl)methyl]-4,6-di-tert-butylphenolate, Nu=NMe(2) (1), N(SiMe(3))(2) (3), OSiPh(3) (6); LO(2)=2,4-di-tert-butyl-6-(morpholinomethyl)phenolate, Nu=N(SiMe(3))(2) (7), OSiPh(3) (8)) and the homoleptic Sn{LO(1)}(2) (2) have been synthesized. The alkoxy derivatives [Sn{LO(1)}(OR)] (OR=OiPr (4), (S)-OCH(CH(3))CO(2)iPr (5)), which were generated by alcoholysis of the parent amido precursor, were stable in solution but could not be isolated. [Sn{LO(1)}](+)[H(2)N{B(C(6)F(5))(3)}(2)](-) (9), a rare well-defined, solvent-free tin cation, was prepared in high yield. The X-ray crystal structures of compounds 3, 6, and 8 were elucidated, and compounds 3, 6, 8, and 9 were further characterized by (119)Sn Mössbauer spectroscopy. In the presence of iPrOH, compounds 1-5, 7, and 9 catalyzed the well-controlled, immortal ring-opening polymerization (iROP) of L-lactide (L-LA) with high activities (ca. 150-550 mol(L-LA) mol(Sn)(-1) h(-1)) for tin(II) complexes. The cationic compound 9 required a higher temperature (100 °C) than the neutral species (60 °C); monodisperse poly(L-LA)s were obtained in all cases. The activities of the heteroleptic pre-catalysts 1, 3, and 7 were virtually independent of the nature of the ancillary ligand, and, most strikingly, the homoleptic complex 2 was equally competent as a pre-catalyst. Polymerization of trimethylene carbonate (TMC) occurs much more slowly, and not at all in the presence of LA; therefore, the generation of PLA-PTMC copolymers is only possible if TMC is polymerized first. Mechanistic studies based on (1)H and (119)Sn{(1)H} NMR spectroscopy showed that the addition of an excess of iPrOH to compound 3 yielded a mixture of compound 4, compound [Sn(OiPr)(2)](n) 10, and free {LO(1)}H in a dynamic temperature-dependent and concentration-dependent equilibrium. Upon further addition of L-LA, two active species were detected, [Sn{LO(1)}(OPLLA)] (12) and [Sn(OPLLA)(2)] (14), which were also in fast equilibrium. Based on assignment of the (119)Sn{(1)H} NMR spectrum, all of the species present in the ROP reaction were identified; starting from either the heteroleptic (1, 3, 7) or homoleptic (2) pre-catalysts, both types of pre-catalysts yielded the same active species. The catalytic inactivity of the siloxy derivative 6 confirmed that ROP catalysts of the type 1-5 could not operate according to an activated-monomer mechanism. These mechanistic studies removed a number of ambiguities regarding the mechanism of the (i)ROPs of L-LA and TMC promoted by industrially relevant homoleptic or heteroleptic Sn(II) species.

Coordination of a chiral tin(ii) cation bearing a bis(oxazoline) ligand with tetrahydrofuran derivatives

The reaction of SnCl(2) with the lithio derivative of a bis(oxazoline) ligand precursor afforded the enantiomeric chlorostannylene whose chloride ion can be substituted by several neutral or anionic Lewis donors. Abstraction of the chloride ion from the chlorostannylene with silver salts gave the corresponding tetrahydrofuran (THF) complexes of a chiral tin(ii) cation in 1,2-dimethoxyethane (DME) containing THF. That is, the reaction with silver hexafluoroantimonate (AgSbF(6)) afforded the THF complex without interaction with the counteranion. In contrast, reaction with silver triflate (AgOTf) gave the THF complex whose tin center had a pseudo-trigonal bipyramidal structure with two nitrogen atoms of a bidentate ligand and a lone pair at the equatorial positions and one of the oxygen atoms of triflate and an oxygen atom of THF at the apical positions in the solid state. Use of 3-methyltetrahydrofuran (3-MeTHF) instead of THF afforded the 3-MeTHF complexes, where the R-enantiomer of 3-MeTHF predominantly coordinates to the tin center. The previously reported germanium(II) analogue of the tin(II) cation indicated a similar enantioselectivity for the coordination of 3-MeTHF on the germanium center.

Synthesis, structural characterization and in vitro inhibitory studies against human breast cancer of the bis-(2,6-di-tert-butylphenol)tin(iv) dichloride and its complexes

Four new organotin(IV) complexes of bis-(2,6-di-tert-butylphenol)tin(IV) dichloride [(tert-Bu-)(2)(HO-Ph)](2)SnCl(2) (1) with the heterocyclic thioamides 2-mercapto-pyrimidine (PMTH), 2-mercapto-4-methyl-pyrimidine (MPMTH), 2-mercapto-pyridine (PYTH) and 2-mercapto-benzothiazole (MBZTH), of formulae {[(tert-Bu-)(2)(HO-Ph)](2)Sn(PMT)(2)} (2), {[(tert-Bu-)(2)(HO-Ph)](2)Sn(MPMT)(2)} (3), {[(tert-Bu-)(2)(HO-Ph)](2)SnCl(PYT)} (4) and {[(tert-Bu-)(2)(HO-Ph)](2)SnCl(MBZT)} (5), have been synthesized and characterized by elemental analysis, (1)H-, (13)C-, (119)Sn-NMR, EPR, FT-IR, Raman and Mössbauer spectroscopic techniques. The crystal and molecular structures of compounds 1–5 have been determined by X-ray diffraction. The geometries around the metal center adopted in complexes 1–5 varied between tetrahedral in 1, trigonal bipyramidal in 3, 4, 5 and distorted octahedral in 2. Two carbon atoms from aryl groups and two chlorine atoms form a distorted tetrahedron in the case of 1. Two carbon, two sulfur and two nitrogen atoms from thione ligands form a distorted octahedral geometry around tin(IV) with trans-C(2), cis-N(2), cis-S(2)-configurations in 2. However, in the case of 4 and 5 complexes two carbon, one sulfur, one nitrogen and one chloride atom form a distorted trigonal bipyramidal arrangement. Finally, in the case of 3 the trigonal bipyramidal geometry is achieved by two carbon, two sulfur and one nitrogen atom in a unique coordination mode of thioamides toward the tin(IV) cation. Compounds 1–5 were tested for their in vitro cytotoxicity against the human breast adenocarcinoma (MCF-7) cell line. Compound 3 exhibits strong cytotoxic activity against MCF-7 cells (IC(50) = 0.58 ± 0.1 μM).