Synthesis and characterisation of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) Zr(IV) monothiophosphate composite cation exchanger: analytical application in the selective separation of lead metal ions

In this study, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) zirconium(IV) monothiophosphate composite cation exchanger was prepared by sol–gel precipitation method. The presence of sulphur in the cation exchanger enhances affinity towards the heavy metal ions which can improve the selectivity of the material. The selectivity studies showed that the material is selective towards Pb(II) ions. To characterise the material, several physicochemical properties were also studied which includes X-ray, scanning electron microscopy and transmission electron microscopy studies. The ion-exchange behaviour of this cation exchanger was studied by using some of the selected properties like ion-exhange capacity for various metal ions, elution, effect of eluent concentration, thermal effect on ion-exchange capacity (IEC). The results of IEC and physicochemical properties revealed that the material is nanocomposite, crystalline, chemically, mechanically and thermally stable. The analytical ability of this cation exchanger was demonstrated in binary separation of Pb(II) ions from a mixture of other metal ions. The recovery is qualitative and the separations are reproducible.     

Synthesis,spectra, crystal structures and anticancer studies of 26‐membered macrocyclic dibutyltin(IV) dithiocarbamate complexes: Single‐source precursors for tin sulfide nanoparticles

Four new macrocyclic dinuclear dibutyltin(IV) dithiocarbamate complexes of the type [Bu₂Sn(dtc)]₂, where dtc = hexane‐1,6‐diylbis(4‐fluorobenzyldithiocarbamate) anion ( 1 ), hexane‐1,6‐diylbis(4‐chlorobenzyldithiocarbamate) anion ( 2 ), hexane‐1,6‐diylbis(furfuryldithiocarbamate) anion ( 3 ) and hexane‐1,6‐diylbis(pyrrole‐2‐ylmethyldithiocarbamate) anion ( 4 ), have been prepared. The dithiocarbamate ligands efficiently self‐assemble with Bu₂Sn(IV) to form bimetallic 26‐membered macrocycles. All the complexes have been characterized using elemental analysis, infrared and NMR (¹H and ¹³C) spectroscopies and X‐ray crystallography. Single‐crystal X‐ray diffraction analysis of all the complexes confirms the formation of the dinuclear metallomacrocycles in which dithiocarbamate ligands are asymmetrically bound to the tin atoms. The coordination sphere around the tin atom in 1 – 4 can be described as a skew trapezoidal bipyramid. The dimensions of the cavity of the macrocycles of 1 – 4 are ca 8.0 × 9.0 Å². Complexes 1 – 4 were evaluated for their in vitro anticancer activity against MCF‐7 and HL‐60 cells. Complexes 1 and 2 are more active against MCF‐7 and HL‐60. Thermal decomposition of 1 and 4 yielded tin sulfides. They were characterized using powder X‐ray diffraction (PXRD), high‐resolution transmission electron microscopy and UV diffuse reflectance and energy‐dispersive X‐ray spectroscopies. PXRD studies reveal that the as‐prepared tin sulfides are composed of orthorhombic phase of SnS.     

Tin(IV) complexes of 2‐benzoylpyridine N(4)‐phenyl‐thiosemicarbazone: spectral characterization,structural studies and antifungal activity

Three tin(IV) complexes of 2‐benzoylpyridine N(4)‐phenylthiosemicarbazone (H2Bz4Ph) were prepared: [Sn(L)Cl₃] (1), [BuSn(L)Cl₂] (2) and [(Bu)₂Sn(L)Cl] (3), in which L stands for the anionic ligand formed upon complexation with deprotonation and release of HCl. The complexes were characterized by a number of spectroscopic techniques. The crystal structures of H2Bz4Ph and complex 3 were determined. The antifungal activity of the ligand and its tin(IV) complexes was tested against Candida albicans. The thiosemicarbazone proved to be more active than the tin(IV) complexes. Copyright © 2003 John Wiley & Sons, Ltd.     

Cation–Cation Interactions,Magnetic Communication,and Reactivity of the Pentavalent Uranium Ion [U(NtBu)2]+

Communication is important : The dimeric bis(imido) uranium complex [{U(NtBu)₂(I)(tBu₂bpy)}₂] (see picture; U green, N blue, I red) has cation–cation interactions between [U(NR)₂]⁺ ions. This f¹–f¹ system also displays f orbital communication between uranium(V) centers at low temperatures, and can be oxidized to generate uranium(VI) bis(imido) complexes.

     

The first polymorph, κ″-(ET)2Cu[N(CN)2]Cl, in the family of κ-(ET)2Cu[N(CN)2]X (X=Cl, Br, I) radical cation salts

The first polymorph, κ″-(ET)₂Cu[N(CN)₂]Cl, of the well known Mott insulator κ-(ET)₂Cu[N(CN)₂]Cl has been prepared and its crystal and electronic structures have been examined. The polymorph has monoclinic symmetry in contrast with the orthorhombic one of the isostructural κ-salts of the family (ET)₂Cu[N(CN)₂]X (X=Cl, Br, I). The monoclinic phase exhibits a layered structure in which the conducting layers are packed in a κ-type arrangement and the anion sheets consist of polymeric zigzag chains formed by Cu[N(CN)₂]Cl units. The main structural differences with the orthorhombic κ-salts are that the anion sheets are disordered and the ET molecules are less planar. The new polymorph shows metallic type resistivity down to 4.2 K.     

N → Sn coordination in the complexes of tin halides with pyridine: A comparison between Sn(II) and Sn(IV)

The experimentally well‐known complexation of tin(II) and tin(IV) halides with pyridine (py) leads to structures showing N → Sn coordination. In the present work, the complexes SnX_n·mpy (where X = F, Cl, Br, I; n = 2, 4; m = 1, 2) possessing this kind of coordination were studied using a computational quantum chemical approach. Various aspects in the theoretical picture of these complexes were examined to find similarities and differences in their N → Sn coordination. The aspects included, among others, the physical nature of intermolecular interactions, and their role in establishing the structure and energetic stabilization of the complexes. In this context, the effect of tin valency was inspected in great detail. As proven by several theoretical methods, a largely ionic character with a certain covalent component can be attributed to the studied N → Sn coordination, irrespective of tin valency. All complexes are destabilized by py‐py and three‐body interactions, but the Sn(II) complexes experience it to a greater extent. Marked differences are observed in the structural behavior of N → Sn and SnX_n during complex formation. This affects the energetics of complexation and, in consequence, the penta‐coordinated Sn(IV) center shows a higher propensity to expand its coordination number, compared with the tri‐coordinated Sn(II) center. The present study supplements the experimental characterization of SnX_n·mpy and, in general, it sheds light on the coordination of heteroaromatic nitrogen to tin. The survey of the Cambridge Structural Database revealed that such coordination occurred in a number of crystal structures.     

Heteroleptic Tin(II) Initiators for the Ring‐Opening (Co)Polymerization of Lactide and Trimethylene Carbonate: Mechanistic Insights from Experiments and Computations

The tin(II) complexes {LO^x}Sn(X) ({LO^x}^?=aminophenolate ancillary) containing amido ( 1 – 4 ), chloro ( 5 ), or lactyl ( 6 ) coligands (X) promote the ring‐opening polymerization (ROP) of cyclic esters. Complex 6 , which models the first insertion of L ‐lactide, initiates the living ROP of L ‐LA on its own, but the amido derivatives 1 – 4 require the addition of alcohol to do so. Upon addition of one to ten equivalents of iPrOH, precatalysts 1 – 4 promote the ROP of trimethylene carbonate (TMC); yet, hardly any activity is observed if tert‐butyl (R)‐lactate is used instead of iPrOH. Strong inhibition of the reactivity of TMC is also detected for the simultaneous copolymerization of L ‐LA and TMC, or for the block copolymerization of TMC after that of L ‐LA. Experimental and computational data for the {LO^x}Sn(OR) complexes (OR=lactyl or lactidyl) replicating the active species during the tin(II)‐mediated ROP of L ‐LA demonstrate that the formation of a five‐membered chelate is largely favored over that of an eight‐membered one, and that it constitutes the resting state of the catalyst during this (co)polymerization. Comprehensive DFT calculations show that, out of the four possible monomer insertion sequences during simultaneous copolymerization of L ‐LA and TMC: 1) TMC then TMC, 2) TMC then L ‐LA, 3) L ‐LA then L ‐LA, and 4) L ‐LA then TMC, the first three are possible. By contrast, insertion of L ‐LA followed by that of TMC (i.e., insertion sequence 4) is endothermic by +1.1 kcal mol^?1, which compares unfavorably with consecutive insertions of two L ‐LA units (i.e., insertion sequence 3) (?10.2 kcal mol^?1). The copolymerization of L ‐LA and TMC thus proceeds under thermodynamic control.     

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{LOⁿ}(Nu)] (LO¹=2‐[(1,4,7,10‐tetraoxa‐13‐azacyclopentadecan‐13‐yl)methyl]‐4,6‐di‐tert‐butylphenolate, Nu=NMe₂ ( 1 ), N(SiMe₃)₂ ( 3 ), OSiPh₃ ( 6 ); LO²=2,4‐di‐tert‐butyl‐6‐(morpholinomethyl)phenolate, Nu=N(SiMe₃)₂ ( 7 ), OSiPh₃ ( 8 )) and the homoleptic Sn{LO¹}₂ ( 2 ) have been synthesized. The alkoxy derivatives [Sn{LO¹}(OR)] (OR=OiPr ( 4 ), (S)‐OCH(CH₃)CO₂iPr ( 5 )), which were generated by alcoholysis of the parent amido precursor, were stable in solution but could not be isolated. [Sn{LO¹}]⁺[H₂N{B(C₆F₅)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 ¹¹⁹Sn 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 ¹H and ¹¹⁹Sn{¹H} 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 {LO¹}H in a dynamic temperature‐dependent and concentration‐dependent equilibrium. Upon further addition of L ‐LA, two active species were detected, [Sn{LO¹}(OPLLA)] ( 12 ) and [Sn(OPLLA)₂] ( 14 ), which were also in fast equilibrium. Based on assignment of the ¹¹⁹Sn{¹H} 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.     

Octahedral Tin(IV) Complexes of the Chalcogen‐Centered Ligands [EC(PPh2S)2]2– (E = S,Se)

The metathetical reactions between SnBr₄ and Li₂[E'C(PPh₂E)₂] in toluene produce the homoleptic tin(IV) complexes Sn[E′C(PPh₂E)₂]₂ [E = E′ = S ( 1b ); E = S, E′ = Se ( 1c )], which were isolated as red crystals and structurally characterized by X‐ray crystallography. The metrical parameters of these octahedral complexes are compared with those of the all‐selenium analog Sn[E′C(PPh₂E)₂]₂ (E = E′ = Se, 1a ), which was prepared previously by a different route.     

Molecular Mechanics Calculations on Chelates of Titanium(IV), Vanadium(IV/V), Copper(II), Nickel(II), Molybdenum(IV/V), Rhenium(IV/V) and Tin(IV) with Di- and Tridentate Ligands Using the New Extensible Systematic Force Field (ESFF)—An Empirical Study

Force field calculations were performed on a series of 27 transition metal complexes of titanium(IV), vanadium(IV/V), copper(II), nickel(II), molybdenum(IV/V), rhenium(IV/V), and tin(IV) with a broad variety of di- or tridentate ligands in order to find a reliable scheme for determining the molecular structure of such chelates with the new Extensible Systematic Force Field (ESFF). A good agreement between theoretical results and experimental data was achieved. In some cases an unspecific fitting of the force field was necessary.     

Synthesis,characterization, biological studies and in vitro cytotoxicity on human cancer cell lines of titanium(IV) and tin(IV) derivatives with the α,α′‐dimercapto‐o‐xylene ligand

The reaction of α,α′‐dimercapto‐o‐xylene (H₂dmox) with different precursors such as SnMe₂Cl₂, [Ti(η⁵‐C₅H₅)₂Cl₂] and [Ti(η⁵‐C₅H₄Me)₂Cl₂] (1:1) in the presence of two equivalents of NEt₃ yielded the complexes [SnMe₂(dmox)] (1), [Ti(η⁵‐C₅H₅)₂(dmox)] (2) and [Ti(η⁵‐C₅H₄Me)₂(dmox)] (3), respectively. 1–3 have been characterized by spectroscopic methods; in addition, complex 3 has been determined by X‐ray diffraction studies. Furthermore, structural studies based on density functional theory calculations of 1 and 2 have been carried out. The cytotoxic activity of 1–3 was tested against the tumour cell lines human adenocarcinoma HeLa, human myelogenous leukaemia K562 and human malignant melanoma Fem‐x. The results of this study show a higher cytotoxicity of the tin(IV) complex (1) in comparison to their titanium(IV) counterparts (2 and 3) as well as an improvement in the cytotoxic activity of compounds 2 and 3 compared to their titanocene(IV) dichloride analogues [Ti(η⁵‐C₅H₅)₂Cl₂] and [Ti(η⁵‐C₅H₄Me)₂Cl₂]. In view of the relatively high cytotoxicity of compound 1, a detailed study on the effects of the in vitro treatment of cancer cell lines using this compound was carried out. Thus cell cycle experiments on all the studied cell lines treated with 1 show that this complex seems to cause disturbances in the G1 phase of HeLa, and in the G1 and G2/M phases of Fem‐x cell line, while almost no disturbances were observed in the cycle of K562 cells treated with 1. Finally, DNA laddering method showed that treatment of the HeLa and Fem‐x cell lines with IC₉₀ doses of 1 resulted in the induction of apoptosis. Copyright © 2012 John Wiley & Sons, Ltd.     

New palladium(II)–N‐heterocyclic carbene complexes containing benzimidazole‐2‐ylidene ligand derived from menthol: synthesis,characterization and catalytic activities

A new series of sterically hindered ligands containing (1R,2S,4R)‐(+)‐menthoxymethyl group attached to benzimidazole‐based N‐heterocyclic carbene (NHC), palladium–bis‐NHC complexes and (κ²‐C,N)‐palladacyclic NHC complexes have been synthesized and characterized using appropriate spectroscopic techniques. Catalytic performance of the palladium complexes has been investigated for allylic alkylation, Suzuki and Heck carbon–carbon coupling reactions. These complexes smoothly catalyse the carbon–carbon bond formation reactions. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation,antitumor activity in mice,pharmacokinetics and tissue distribution in rats of di‐n‐butyl‐di‐(4‐chlorobenzohydroxamato)tin(IV) liposome

Di‐n‐butyl‐di‐(4‐chlorobenzohydroxamato)tin(IV) (DBDCT) is an antitumor compound with high activity and relatively low bioavailability. In order to improve the pharmacokinetic characteristics and raise its therapeutic index, a liposome of DBDCT (DBDCT‐L) was prepared for the first time. A study of the pharmacokinetics and tissue distribution after intravenous administration of DBDCT‐L compared with free DBDCT to rats was investigated. DBDCT‐L showed a slower clearance, increased half‐time and a larger AUC value than those of free DBDCT, which demonstrated that DBDCT‐L could significantly alter the tissue distribution pattern of DBDCT in rats. The highest concentration distribution for DBDCT‐L was detected in liver, which may be associated with the enhanced antitumor activity in vivo against hepatocellular carcinoma H₂₂ and possible target release of the compound. Acute toxicity assay showed that the LD₅₀ value of DBDCT‐L was higher than that of free DBDCT. Further in vivo antitumor test showed that DBDCT‐L displayed higher antitumor activity against the hepatocellular carcinoma H₂₂ than free DBDCT, indicating that the liposome could prolong the action time of DBDCT in the system circulation, change its distribution in rats, reduce acute toxicity and finally increase antitumor activity. Copyright © 2014 John Wiley & Sons, Ltd.     

New Insights into the Reactivity of Cisplatin with Free and Restrained Nucleophiles: Microsolvation Effects and Base Selectivity in Cisplatin–DNA Interactions

The reactivity of cisplatin towards different nucleophiles has been studied by using density functional theory (DFT). Water was considered first to analyze the factors that govern the transformation of cisplatin into more electrophilic aquated species by using an activation‐strain model. It was found that the selectivity and reactivity of cisplatin is a delicate trade‐off between strain and interaction energies and that the second chloride is a worse leaving group than the first. When similar studies were carried out with imidazole, guanine (G), and adenine (A), it was found that in general the second nucleophilic substitution reactions have lower activation barriers than the first ones. Finally, simulations of the structural restrictions imposed by the DNA scaffold in intra‐ and interstrand processes showed that the geometries of the reaction products are nonoptimal with respect to the unrestrained A and G nucleophiles, although the energetic cost is not considerable under physiological conditions, which thus permits nucleophilic substitution reactions that lead to highly distorted DNA.     

Organic–inorganic poly(N‐vinylpyrrolidone) copolymers with double‐decker silsesquioxane in the main chains: Synthesis,glass transition,and self‐assembly behavior

An organic–inorganic copolymer with polyhedral oligomeric silsesquioxane (POSS) and xanthate moieties in the main chain was synthesized via the polycondensation between 3,13‐di(2‐bromopropionate)propyl double‐decker silsesquioxane (DDSQ) and 1,4‐di(xanthate potassium)butane. This hybrid copolymer was used as the macromolecular chain transfer agent to obtain the organic–inorganic poly(N‐vinylpyrrolidone) (PVPy) copolymers via a reversible addition fragmentation chain transfer/macromolecular design via the interchange of xanthates (RAFT/MADIX) polymerization approach; the polymerization behavior of N‐vinyl pyrrolidone was investigated by means of gel permeation chromatography. It was found that the polymerization was in a living and controlled manner. Transmission electron microscopy (TEM) showed that the organic–inorganic PVPy copolymers with DDSQ in the main chains were microphase‐separated in bulks. Compared to plain PVPy, the organic–inorganic PVPy copolymers displayed the decreased glass transition temperatures (T_gs); the decreased T_gs are attributable to the effect of the introduced DDSQ cages on the packing of PVPy chains as evidenced by means of Fourier transform infrared spectroscopy (FTIR). In water, the organic–inorganic PVPy copolymers can self‐assemble into the spherical nano‐objects with the size of 20–50 nm in diameter. In the self‐assembled nano‐objects, the aggregates of the hydrophobic DDSQ constituted the cores of the polymeric micelles whereas the PVPy chains between the DDSQ behaved as the coronas of the polymeric micelles. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2949–2961     

New diorganotin(IV) complexes of Schiff base derived from 4‐amino‐3‐hydrazino‐5‐mercapto‐4H‐1,2,4‐triazole: Synthesis,structural characterization,density functional theory studies,atoms‐in‐molecules analysis and antifungal activity

New diorganotin(IV) complexes of a Schiff base (HL) having general formula R₂Sn(L)Cl (where L is the monoanion of HL and R = n‐Bu or Ph) have been synthesized and characterized using elemental analysis, infrared, NMR (¹H, ¹³C, ¹¹⁹Sn) and UV–visible spectroscopies and mass spectrometry. These investigations suggest that in these 1:1 monomeric derivatives the Schiff base ligand acts in a monoanionic bidentate manner coordinating through the O_phenolic and N_azomethine, with proposed distorted trigonal bipyramidal geometry around tin with O_phenolic and two organic groups in the equatorial plane and the N_azomethine and the third organic group in axial positions. The proposed structures have been validated by density functional theory (DFT)‐based quantum chemical calculations at the B3LYP/6‐31G(d,p)/Def2‐SVP (Sn) level of theory. The simulated UV–visible spectrum was obtained with the time‐dependent DFT method in the gas phase and in the solvent field with the integral equation formalism–polarizable continuum model. A comparative analysis of the experimental vibrational frequencies and simulated harmonic frequencies indicates a good correlation between them. An insight into the intramolecular bonding and interactions among bonds in organotin(IV) complexes of HL was obtained by means of natural bond orbital analysis. The topological and energetic properties of the electron density distribution for the tin–ligand interaction in R₂Sn(L)Cl have been theoretically calculated at the bonds around the central tin atom in terms of atoms‐in‐molecules theory. The R₂Sn(L)Cl complexes were screened for their in vitro antifungal activity against chosen fungal strains.     

The analyses of alkyllead compounds in fish and environmental samples in Ontario,Canada (1981–1987)

Analyses of fish and other environmental samples (clams, macrophytes, sediments and waters) from areas upstream and downstream from two alkyllead manufactures beside the St Lawrence and St Clair Rivers, Ontario, show a clear indication of elevated alkyllead levels in samples near the industries. Most species of fish contained alkyllead compounds with tetraethyllead and triethyllead as the predominant forms. Most fish from the contaminated areas contained 50–75% of total lead as alkylleads. Carp, yellow perch and white sucker were generally the most contaminated species while pike, alewife and rock bass were the least contaminated. Average alkyllead levels varied from year to year but declined steadily after 1981. For example, the geometric mean of alkyllead compounds in carp from the St Lawrence River decreased from 4207 μg kg^?1 in 1981 to 2000 μg kg^?1 in 1982 and to 49 μg kg^?1 in 1987, reflecting the reduction of alkylleads in the effluents and the closure of one of the manufactures in 1985. Alkyllead levels were consistently lower in muscle and carcass samples in comparison with whole fish containing fatty intestines. However, muscle levels were generally equal to carcass levels. The concentrations of alkyllead compounds were generally low in clams, macrophytes, sediments and waters except from the immediate vicinity of the manufactures' final effluent discharges.