Search

In a first part, the impact of low temperature operation on the classical short channel effects will be discussed critically. Particular attention will be given to the reduction of the threshold voltage VTwith effective device length in the temperature range 4.2 K to 300 K and to the short-channel behaviour of the subthreshold swing 1/S. In a second part, the impact of dopant freeze-out on the static operation of deep submicron n-MOSFETs will be studied. A comparison is made between standard 0.25 µm B doped and exploratory 0.1 µm In doped transistors. Although the experimental threshold voltage behaviour of deep submicron MOSFETs at cryogenic temperatures can be qualitatively described by the standard equations, a significant difference is noted between the measured and the calculated VT, which is most pronounced in the liquid helium temperature range. Possible additional factors which should be taken into account in a refined modeling will be pointed out, with particular emphasis on the contribution of the interface state charge.

The complex {[(CH3)2Sn]2[(CH3)2SnO](OCH3)(HONZO)(ONZO)} (3) [ONZOH is the oximate residue, o-(–ON=CH–C6H4–OH), HONZO the corresponding phenolate residue, o-(HON=CH–C6H4–O–), and ONZO the dibasic species o-(–ON=CH–C6H4–O–), all derived from salicylaldoxime, o-(HON=CH–C6H4–OH)] reacts with an excess of racemic (d,l)-2-methyl-1-butanol to afford the μ2-substitution product 5a {[(CH3)2Sn]2[(CH3)2SnO][OCH2CH(CH3)CH2CH3](HONZO)(ONZO)]}. Crystallographic characterisation of the trinuclear microcluster 5a shows the presence of the monobasic HONZO ligand in a tridentate μ2-O,N mode and of the dibasic ONZO ligand in a tridentate O,N,O mode. This coordination mode leads to one seven-coordinate and two five-coordinate tin centers that are linked by a μ3-oxo function. The coordination geometries are distorted pentagonal bipyramidal and trigonal bipyramidal, respectively. The two low-coordinate tin atoms are linked by the alkoxide ion. The corresponding chiral (S)-2-methyl-1-butanol reacts analogously to yield 5b. By contrast, reaction of 3 with chiral secondary alcohols (2-butanol or 1-phenyl-1-ethanol), in various molar ratios, failed to provide the corresponding μ2-alkoxy complex. Instead, pure crystals of {[(CH3)2Sn]2[(CH3)2SnO](OH)(HONZO)(ONZO)} (2a) were isolated.

Leakage reduction is crucial for metal--insulator--metal (MIM) capacitors for future dynamic random access memory (DRAM) nodes. In previous investigations we showed that increasing the Sr-content would result in leakage reduction of SrTiO3(STO) films deposited on TiN. In this work we demonstrate for thin (10 nm) stoichiometric SrTiO3films that the leakage properties can be significantly lowered (while keeping high capacitance densities) by using stacking approaches such as seed layer (thin STO layer crystallized before the “bulk” STO deposition) and multistack SrTiO3/GdAlO3/SrTiO3. In this work, SrTiO3films are deposited using a low temperature ALD process enabling the use of low-cost, manufacturable-friendly TiN-bottom electrode.

We report a comprehensive evaluation and overview of the latest developments and technology challenges of FinFET-based devices. They offer improved electrostatics and steeper sub-threshold slopes, attractive for enabling further CMOS scaling, but can also suffer from higher parasitic resistance and parasitic capacitance for narrow Fin devices. Critical solutions to minimize the impact of the latter are here addressed, demonstrating their viability for replacing planar CMOS devices. Multiple-VT CMOS can be achieved with capping technology, with aggressively scaled Ring Oscillators (RO) and SRAM cells showing excellent performance and matching behavior.

The state diagram of a blend consisting of a copolymer containing ethylene oxide and propylene oxide, P(EO‐ran‐PO), and poly(ether sulfone), PES, is constructed by using modulated‐temperature differential scanning calorimetry (MTDSC), T2NMR relaxometry, and light scattering. The apparent heat capacity signal in MTDSC is used for the characterization of polymer miscibility and morphology development. T2NMR relaxometry is used to detect the onset of phase separation, which is in good agreement with the onset of phase separation in the apparent heat capacity from MTDSC and the cloud‐point temperature as determined from light scattering. The coexistence curve can be constructed from T2values at various temperatures by using a few blends with well‐chosen compositions. These T2values also allow the detection of the boundary between the demixing zones with and without interference of partial vitrification and are in good agreement with stepwise quasi‐isothermal MTDSC heat capacity measurements. Important interphases are detected in the heterogeneous P(EO‐ran‐PO)/PES blends.

In this paper we demonstrate the successful integration of in-situ doped embedded Si:C stressors epitaxially grown in the source and drain areas of nMOS devices using a novel Cyclic Deposition Etch (CDE) process. These layers have substitutional C content ranging between 1% and 2% with potential of achieving even higher substitutional carbon concentration. Another distinctive feature of this process is that it allows for high in-situ P doping for ease of integration within a CMOS platform. We demonstrate superior performance of strained nMOS devices with embedded Si:C showing up to 12.5% on-state current improvement over the unstrained reference process. We report on material characterization results of embedded Si:C stressors, in particular, strain retention properties as a function of subsequent post-epitaxy processing.

Diffusion‐ordered NMR spectroscopy (DOSY NMR) is presented as a tool for the determination of the diffusion coefficients of organic ligands in suspensions of titanium dioxide nanoparticles. The nanoparticles were prepared by a sol‐gel process by hydrolysis and condensation reactions of titanium tetra‐n‐butoxide in the presence of pentane‐2,4‐dione (acacH: acetylacetone), as well as para‐toluenesulfonic acid (pTsA) and n‐butanol (nBuOH). NMR spectroscopic studies were performed in various deuterated solvents, on both dispersed xerosols and diluted sols. The bipolar‐pulsed field gradient longitudinal eddy‐current delay (LED) pulse sequence was used for data acquisition. The data were processed by inverse Laplace transformation (ILT), by using a maximum entropy algorithm, to afford 2D DOSY spectra. Different diffusion regimes for organic ligands in the bound and unbound states were successfully discriminated, more particularly in [D3]acetonitrile, thus allowing assessment of their interactions with the nanoparticles.

Using strain to boost transistor performance and the use of metal gate electrodes are both considered to be key enablers for further improvements in device performance. This paper discusses the combination of Si1-xGex S/D, used as a pMOS stressor, with two metal gate options: inserted metal gates and FUSI

An overview of FUSI gates, emphasizing on Ni-based materials for applications into sub-45 nm CMOS is presented. The work function of FUSI gates was investigated, finding lower values (suitable for NMOS) for 1) gate stacks containing lanthanides (such as Yb) for SiON or HfSiON, 2) NiSi with dopants (Sb, As and P) on SiO2 or SiON and 3) Si-richer silicides (e.g. monosilicides) for HfSiON. Higher WF values (adequate for PMOS) were found for 1) Pt containing silicides on SiO2 or SiON, 2) Ni or Pt metal-rich silicides on HfSiON and 3) B doped NiSi or Al doped Ni-rich silicides on SiO2 or SiON. Several of these FUSI gates were implemented in transistors demonstrating |Vt| values down to ~0.25-0.3 V. The scalability and integration issues are discussed, demonstrating good device characteristics down to ~50 nm gatelengths for optimized process conditions. Finally, a dual WF Ni FUSI CMOS integration flow is demonstrated.

Study of Hf based high-k gate stack, HfO2 and its silicate, prepared by PVD-high k dielectric and Ni-Fully Silicide(FUSI) gate focusing on interfacial reaction between high-k and Ni- FUSI electrode is overviewed. Effects of SiN capping between Ni-FUSI gate and high-k dielectric and post deposition anneal (PDA) to suppress the reaction during FUSI process were investigated. The SiN cap could increase transistor yield and PDA could suppress instability of the drive current due to defects/roughness caused by interfacial reaction during NiSi formation. It is noteworthy that not only elimination of poly- depletion but also EOT reduction was observed by replacing the poly Si with the Ni-FUSI, which was remarkable for Ni- FUSI/SiON than HfO2 case. Hereof, by optimizing the PDA condition with SiN cap, decent electrical characteristics were obtained, Ion(n/p) > 600/200 uA/um at Ioff = 20 pA/um at Vdd = 1.1V. This drivability meets low stand-by power specification of the MOSFET for 45nm node.

A series of 4-amino-tetrahydro-2-benzazepin-3-one derivatives (Ac–Aba–Xxx–NHMe) were prepared as tetrapeptide mimetics. Considering the structural resemblance with the so-called Freidinger lactams, their propensity to adopt a β-turn conformation was investigated by NMR spectroscopy (solvent and temperature dependence) and molecular modeling. Interestingly, most of these lactams adopt extended conformations, only the spiro-benzazepinone 9 has a strong preference for the formation of a β-turn. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Dialkyltin dichloride grafted to a cross‐linked polystyrene, with the formula [PH](1−t)[P(CH2)nSnBuCl2]t(P=[CH2CH(pC6H4)], t=the degree of functionalization, and n=6 or 11), is investigated as a recyclable catalyst in the ring‐opening polymerization (ROP) of ε‐caprolactone (CL). It is demonstrated that high‐resolution magic‐angle‐spinning (HR‐MAS) NMR spectroscopy is an invaluable tool to characterize completely the supported catalyst. The 2D 1H–13C HSQC HR‐MAS spectrum, in particular, allowed extensive assignment of the 1H and 13C resonances, as well as accurate measurement of the nJ(1H–117/119Sn) and nJ(13C–117/119Sn) coupling constants. 1H and 119Sn HR‐MAS NMR spectroscopy is presented as a monitoring tool for catalytic processes based on organotin compounds, particularly for the investigation of the extent to which polymerization residues are observable in situ in the material pores and for the assessment of the chemical integrity and recycling conditions of the grafted catalyst. From polymerization experiments with CL, initiated by n‐propanol and with [PH](1−t)[P(CH2)nSnBuCl2]tof various compositions as the supported catalyst, it appears that a partial 'burst' of the polystyrene support occurs when the length of the alkyl spacer is limited to n=6, as a result of polymer chains growing within the pores of the support. However, extension of the length of the aliphatic polymethylene spacer from 6 to 11 carbon atoms preserves the support integrity and allows the production of catalyst‐deprived poly(ε‐caprolactone) (PCL) oligomers. A preliminary attempt to recycle the heterogeneous catalyst has shown that very good reproducibility can be obtained, in terms of both catalyst activity and molecular‐weight parameters of the as‐recovered PCL polyester chains.

Novel polymeric derivatives of various average molecular weights bearing tributyltin carboxylate moieties as terminal groups have been prepared by esterification with bis(tributyltin) oxide of the corresponding poly(ethylene glycol)s functionalized with dimethylenecarboxylic end groups. Low‐molecular‐weight compounds have also been synthesized, with the aim of investigating the influence of the polymeric chain on tin properties. As investigated by Sn NMR and Fourier transform infrared, the metal center appears to be completely tetracoordinated in chloroform solution at room temperature, whereas at low temperature, the tin atom undergoes a fast exchange between intramolecular pentacoordination with the ethereal oxygen atoms and the unassociated form. In the solid state, even at room temperature, all the polymeric products exhibit both tetracoordination and pentacoordination at tin, the latter achieved by interaction with both ethereal and carbonyl oxygens. The thermal behavior of the series of compounds indicates the presence of crystalline domains in the material, which can be ascribed either to intermolecular interactions at tin, giving rise to organometal aggregates, or to the formation of an ordered phase induced by the presence of the macromolecular chain, depending on the more or less elevated relative concentration of the organotin moieties in the sample. These findings are also confirmed by the X‐ray diffractions patterns of the investigated products. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3091–3104, 2005

Insoluble polystyrene grafted compounds of the type (PH)(1−t){P(CH2)nSnBupCl3−p}t, (PH)(1−t){P(CH2)nSnBuO}tand (PH)(1−t)[{P(CH2)nSnBuCl}2O]t/2, in which (PH) is a cross‐linked polystyrene; n=4, 6, and 11; p=0 and 1; and tthe degree of functionalisation, were synthesised from Amberlite XE‐305, a polystyrene cross‐linked with divinylbenzene. The compounds were characterised by using elemental analysis, and IR, Raman, solid‐state 117Sn NMR, and 1H and 119Sn high‐resolution MAS NMR spectroscopy. The influence of the spacer length and the tin functionality on the catalytic activity of these compounds, as well as their recycling ability, was assessed in the transesterification reaction of ethyl acetate with various alcohols. These studies showed significant differences in the activity of the catalysts interpreted in terms of changes in the mobility of the catalytic centres. Some of the supported catalysts could be recycled at least seven times without noticeable loss of activity. The residual tin content in the reaction products was found to be as low as 3 ppm.

A new precursor molecule for chemical modification of oxide surfaces, the trialkynyl(fluoroorgano)tin(IV) (C4H9−C&tbd1;C)3Sn(CH2)2(CF2)7CF3, 1, was synthesized in three steps from tricyclohexyltin hydride. Compound 1 reacted with Biosepra 100 silica to give chain loadings as high as 0.28 mmol·g^-1 to be compared to 0.44 mmol·g^-1 reached with the trichlorosilane analogue Cl3Si(CH2)2(CF2)7CF3, 2. The modified powders have been thoroughly characterized using elemental analysis, FTIR spectroscopy, solid-state ²⁹Si, ¹³C, and ²⁹Si CP-MAS NMR, XPS, and TGA-MS. Irreversible chemisorption took place in solution at room temperature to give a fluorinated chain thin layer, likely a monolayer, via removal of three hex-1-yne molecules and formation of Sibulk−O−Sn−C linkages. The chemisorption process involves hydrolysis of the precursor in solution before reaction with the silica surface and led to surface-modified silica thermally stable up to 350 °C. Trialkynylorganotins in solution might be therefore advantageously exploited to modify chemically SnO2 or TiO2 surfaces to get dye-sensitized oxide materials able to achieve light-to-electricity conversion.

The present paper describes a method for measuring the molecular diffusion coefficient of fluorescent molecules in microfluidic systems. The proposed static shear-driven flow method allows one to perform diffusion measurements in a fast and accurate manner. The method also allows one to work in very thin i.e.submicron channels, hence allowing the investigation of diffusion in highly confined spaces. In the deepest investigated channels, the obtained results were comparable to the existing literature values, but when the channel size dropped below the micrometer range, a significant decrease more than 30 in molecular diffusivity was observed. The reduction of the diffusivity was most significant for the largest considered molecules ssDNA oligomers with a size ranging between 25 to 100 bases, but the decrease was also observed for smaller tracer molecules FITC. This decrease can be attributed to the interactions of the analyte molecules with the channel walls, which can no longer be neglected when the depth of the channel reaches a critical value. The change in diffusivity seems to become more explicit as the molecular weight of the analytes increases.

Novel polymeric derivatives bearing tributyltin carboxylate moieties in the side chain were synthesized. The coordination at tin in solution and in the solid state was investigated by both Sn‐NMR and FT‐IR: the metal atom appears completely tetracoordinated in chloroform solution, while in the solid state all polymeric products exhibit both tetra‐ and pentacoordination at tin, the latter increasing with the amount of tin containing units. No evidence of tin leaching by hydrolysis of the organometallic ester was observed for these materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5372–5383, 2004

Insoluble polystyrene-grafted compounds of the type [(P−H)(1−t){P−(CH2)6SnBuCl2}t] and [(P−H)(1−t)({P−(CH2)6SnBuX}2O)t/2], where (P−H) represents a cross-linked polystyrene, X is Cl, OH or OOCCH3, and t is the degree of functionalization, were synthesized from Amberlite XE-305, a polystyrene cross-linked with divinylbenzene. The compounds were characterized by elemental analysis, IR and Raman spectroscopy, solid-state 13C and 117Sn NMR spectroscopy and, where appropriate, by 119Sn hr-MAS NMR spectroscopy. The influence of the variable t and tin functionality on the catalytic activity of these compounds was assessed in the transesterification reaction of ethyl acetate with octanol. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Pulsed field gradient 1H NMR spectroscopy has been applied to investigate the association behavior of the Sn12–oxo cluster macrocation [(BuSn)12O14(OH)6]2+with two different and smaller anions, p‐toluenesulfonate (PTS−) and diphenylphosphinate (Ph2PO2−). By monitoring the translational diffusion coefficients of the various species involved, it is shown that the association depends on the anion involved and on the solvent used. Moreover, the possibility to individually monitor the diffusion characteristics of multiple anionic and cationic species in mixtures, by virtue of resolved 1H resonances available from each species, allows us to evidence the occurrence of ion exchange in such systems. Thus when [(BuSn)12O14(OH)6](PTS)2is mixed with two equivalents of Ph2PO2NMe4, PTS−is displaced by Ph2PO2−, highlighting the greater affinity of the organotin macrocation for the diphenylphosphinate. This example clearly illustrates the potential of pulsed field gradient 1H NMR spectroscopy in inorganic/organometallic chemistry, to follow preferential ion pairing in multi‐ion systems at the level of each individually charged species.

Pulsed field gradient ¹H NMR spectroscopy has been applied to investigate the association behavior of the Sn12–oxo cluster macrocation [(BuSn)12O14(OH)6]²⁺ with two different and smaller anions, p-toluenesulfonate (PTS⁻) and diphenylphosphinate (Ph2PO2⁻). By monitoring the translational diffusion coefficients of the various species involved, it is shown that the association depends on the anion involved and on the solvent used. Moreover, the possibility to individually monitor the diffusion characteristics of multiple anionic and cationic species in mixtures, by virtue of resolved ¹H resonances available from each species, allows us to evidence the occurrence of ion exchange in such systems. Thus when [(BuSn)12O14(OH)6](PTS)2 is mixed with two equivalents of Ph2PO2NMe4, PTS⁻ is displaced by Ph2PO2⁻, highlighting the greater affinity of the organotin macrocation for the diphenylphosphinate. This example clearly illustrates the potential of pulsed field gradient ¹H NMR spectroscopy in inorganic/organometallic chemistry, to follow preferential ion pairing in multi-ion systems at the level of each individually charged species.

A large variety of small oxotin clusters, characterised as stable crystalline products or solution transients, has been obtained by the reaction of various diorganotin oxides and salicylaldoxime. The structures were investigated by high resolution multinuclear NMR methods and X-ray crystallography. The predominant trinuclear clusters contain one seven- and two five-coordinate tin atoms and undergo a series of reversible substitution reactions, including those leading to clusters of differing nuclearity, in solution at room temperature. Such a variety of structures is rather unusual in organotin chemistry. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

To study the influence of the stereochemistry on the possibility of cocrystallization of linear and cyclic aliphatic residues in copolyamides, a series of copolyamides 12.6/12.1,4-cyclohexanedicarboxylic acid with variable compositions were synthesized. From solid-state NMR studies it could be deduced that cis-1,4-CHDA is present in the amorphous regions whereas the trans residues are located in both the crystalline and the amorphous phase. WAXD patterns confirm the presence of trans-1,4-CHDA inside the crystals and reveal that the cycloaliphatic ring is most likely oriented in a direction perpendicular to the crystal sheets that contain the hydrogen bonds. As a result, the intersheet distance is increased compared to that of polyamide 12.6. Furthermore, the rings prevent the genesis of a pseudohexagonal phase above the Brill temperature. Exceptionally, crossing rather than merging of the (100) and the combined (010)−(110) WAXD reflections is observed with increasing temperature, indicating that the intersheet distances increase and become larger than the interchain distances within the hydrogen-bonded sheets before the crystals start to melt. Incorporation of trans-1,4-CHDA residues into polyamide 12.6 leads to higher melting temperatures, pointing at cocrystallization in terms of a solid solution rather than as defects. In contrast, a slight melting point depression is observed for copolymers with predominately cis-1,4-CHDA residues.

The Lewis acid-base reaction between Sn(CH3)3X and Y⁻ (with X, Y = F, Cl, Br and I) has been studied using quantum chemical calculations. Complexation energies were calculated at the Density Functional Theory (DFT) level and rationalized on the basis of a local application of the hard and soft acids and bases principle. It was observed that smaller differences in the local softness of the interacting sites in the Lewis acid and base correspond to stronger interactions. Moreover, the calculated sequences in complexation energies can be reproduced using equations containing chemical concepts introduced within the framework of conceptual density functional theory and rooted in the hard and soft acids and bases principle and referring only to the reactants. A method of treating the electronegativity and softness of the halide anions is presented based on a Taylor expansion of the electronegativity of the neutral halogens and the softness-polarizability proportionality. Experimental evidence for the calculated sequences was gathered from measured ¹¹⁷Sn chemical shifts and ¹J (¹³C-^119/117Sn) coupling constant changes upon complexation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Two series of isomeric copolyamides were synthesised, viz.polyamides 12.6 for which the adipic acid residues were partially replaced by cis/trans‐1,4‐cyclohexanedicarboxylic acid (1,4‐CHDA), and polyamides 4.14 for which the 1,4‐diaminobutane residues were partially replaced by cis/trans‐1,4‐diaminocyclohexane (1,4‐DACH). A careful DSC and WAXS analysis learned that only the trans isomers of both 1,4‐DACH and 1,4‐CHDA are incorporated into the crystalline phase. During DSC analysis, an intitial high trans content is preserved in the case of the non‐isomerising 1,4‐DACH, whereas the 1,4‐CHDA residues gradually isomerise from a high initial trans content to a significanly lower trans content. Since these cis residues are not incorporated into the crystalline domains, the lower second heating melting points of the 1,4‐CHDA‐based copolyamides in comparison with 1,4‐DACH‐based copolyamides, having similar cycloaliphatic monomer contents, can be understood.

The ring‐opening polymerization (ROP) of ε‐caprolactone (CL) was carried out in toluene at 100 °C with n‐propanol (nPrOH) in the presence of Bu2SnCl2. It comes out that the molar mass of the polyester chains can be predicted from the initial monomer‐to‐alcohol molar ratio in accordance with a controlled ROP mechanism involving an O‐acyl cleavage of the monomer to selectively form (α‐propyloxy)(ω‐hydroxy)poly(ε‐caprolactone) chains. In order to gain fundamental understanding of the mechanistic factors governing the polyester chain growth, advanced 1H, 13C, and 119Sn NMR investigations were performed in situ in [D8]toluene, as well as with model solutions that contained Bu2SnCl2and binary mixtures of the components at various concentrations and temperatures. This has enabled us to propose a mechanism in which Bu2SnCl2behaves as a catalyst, while nPrOH is the actual initiator. It involves non‐aggregated, six‐coordinate Bu2SnCl2complexes in which ligands exchange fast on the 119Sn NMR observational timescale, and the simultaneous interactions of CL and alcohol function in such a way that it favors insertion/propagation reactions over transesterification ones, up to high monomer conversion.

Copolyamides 2.14/piperazine.14 with variable built-in ratios of 1,2-ethylenediamine (1,2-EDA) and piperazine (pip) were synthesized by solution polycondensation. The built-in ratio of both diamine comonomers was determined with solution ¹³C NMR analysis. The gradual replacement of 1,2-EDA units by cycloaliphatic pip units in polyamide 2.14 resulted in a progressively decreased melting (Tm) and crystallization temperature of the obtained copolyamides. Apparently, the Tm raising effect of the incorporation of rigid cycloaliphatic moieties is overruled by the simultaneous Tm reduction caused by a decreasing hydrogen-bond density. Indications for cocrystallization of 2.14 and pip.14 repeating units were obtained by the thermal analysis of copolyamides 2.14/pip.14 and of a blend of both homopolyamides. A preliminary wide-angle X-ray diffraction study pointed to the same conclusion. Solid-state NMR spectroscopy was used to investigate the influence of the composition on the percentage of the rigid phase of the copolyamides and delivered additional indications for cocrystallization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2082–2094, 2003

The 1 : 2 condensation of dibutyltin(IV) oxide with 1,2‐carborane‐9‐carboxylic acid resulted in bis(1,2‐dicarba‐closo‐dodecaborane‐9‐carboxylato)di‐n‐butyltin (1), the first carborane‐based organotin compound where the carborane cage is linked to the carboxylic moiety via a boron atom. The structure of 1, characterized by 1H, 11B, 13C, 119Sn NMR spectroscopy and X‐ray diffraction, was shown to correspond to bis(1,2‐dicarba‐closo‐dodecaborane‐9‐carboxylato)di‐n‐butyltin. Compound 1was screened in vitroagainst seven tumour cell lines of human origin and was found to be significantly more active than 5‐fluorouracil, cis‐platin and carboplatin but less active than methotrexate and doxorubicin. Copyright © 2003 John Wiley & Sons, Ltd.

The 1 : 2 condensation of dibutyltin(IV) oxide with 1,2-carborane-9-carboxylic acid resulted in bis(1,2-dicarba-closo-dodecaborane-9-carboxylato)di-n-butyltin (1), the first carborane-based organotin compound where the carborane cage is linked to the carboxylic moiety via a boron atom. The structure of 1, characterized by ¹H, ¹¹B, ¹³C, ¹¹⁹Sn NMR spectroscopy and X-ray diffraction, was shown to correspond to bis(1,2-dicarba-closo-dodecaborane-9-carboxylato)di-n-butyltin. Compound 1 was screened in vitro against seven tumour cell lines of human origin and was found to be significantly more active than 5-fluorouracil, cis-platin and carboplatin but less active than methotrexate and doxorubicin. Copyright © 2003 John Wiley & Sons, Ltd.

The reaction of the 2,2‐bis(organodichlorostannyl)propane [(Me3Si)2CH(Cl2)Sn]2CMe2(A) with the corresponding organotin oxide {[(Me3Si)2CH(O)Sn]2CMe2}2(B) does not provide the corresponding normally expected tetraorganodistannoxane {[(Me3Si)2CH(Cl)SnCMe2Sn(Cl)CH(SiMe3)2]O}nbut a complex reaction mixture. One major product, namely the 2,4,6,8‐tetraorgano‐2,6‐dichloro‐1,5,9‐trioxa‐2,4,6,8‐tetrastannabicyclo[3.3.1]nonane derivative [(Me3Si)2CHSnCMe2Sn(Cl)CH(SiMe3)2]2O3(C) was identified in situby 2D 1H119Sn and 1H13C heteronuclear multiple quantum coherence and heteronuclear multiple bond correlation NMR spectroscopy as well as electrospray mass spectrometry. Compound C is proposed to be in equilibrium with an ionic species C′, the cation of which has an adamantane‐type structure. Copyright © 2003 John Wiley & Sons, Ltd.

New organotin(IV) derivatives with general formulae R2SnL, where R = n−Bu and L is the dianion of glycyltyrosine (H2L‐1), glycyltryptophane (H2L‐2), leucyltyrosine (H2L‐3), leucylleucine (H2L‐4), valylvaline (H2L‐5) and alanylvaline (H2L‐6) have been synthesized in 1 : 1 molar ratio by the reaction of Bu2SnO with the respective dipeptide under azeotropic removal of water. Triphenyltin glycylleucinate was obtained by reacting Ph3SnCl and sodium glycylleucinate with filtration of NaCl formed. The bonding and coordination behaviour in these derivatives are discussed on the basis of IR, multinuclear 1H, 13C and 117Sn magnetic resonance and 119Sn Mössbauer spectroscopic studies. These investigations suggest that all the ligands in R2SnL act as dianionic tridentates coordinating through the COO−, NH2and Npeptidegroups, whereas in Ph3Sn(HL) the ligand acts as a bidentate coordinating through the COO−and NH2groups. The 119Sn Mössbauer studies, together with the NMR data, indicate that, for the 1 : 1 monomeric derivatives, the polyhedron around tin in R2SnL is a trigonal bipyramid with the butyl groups and Npeptidein the equatorial positions, while the axial positions are occupied by a carboxylic oxygen and the amino nitrogen atom. In Ph3Sn(HL) the structure is intermediate between pseudotetrahedral and cis‐trigonal bipyramidal, with the Naminoand two phenyl groups in the equatorial plane and the carboxylate oxygen and the third phenyl group in axial positions. All the complexes have been screened against seven cancer cell lines of human origin, viz. MCF‐7, EVSA‐T, WiDr, IGROV, M19, MEL A498 and H226. Ph3Sn(HL) displays the lowest ID50values of the tin compounds tested and reported in this paper. Its activity is comparable to those of methotrexate and 5‐fluorouracil. All the di‐n‐butyltin compounds exhibit lower in vitroanti‐tumour activities than Ph3Sn(HL); however, they do provide significantly better activities than etoposide and cis‐platin. Copyright © 2003 John Wiley & Sons, Ltd.

New organotin(IV) derivatives with general formulae R2SnL, where R = n−Bu and L is the dianion of glycyltyrosine (H2L-1), glycyltryptophane (H2L-2), leucyltyrosine (H2L-3), leucylleucine (H2L-4), valylvaline (H2L-5) and alanylvaline (H2L-6) have been synthesized in 1 : 1 molar ratio by the reaction of Bu2SnO with the respective dipeptide under azeotropic removal of water. Triphenyltin glycylleucinate was obtained by reacting Ph3SnCl and sodium glycylleucinate with filtration of NaCl formed. The bonding and coordination behaviour in these derivatives are discussed on the basis of IR, multinuclear ¹H, ¹³C and ¹¹⁷Sn magnetic resonance and ¹¹⁹Sn Mössbauer spectroscopic studies. These investigations suggest that all the ligands in R2SnL act as dianionic tridentates coordinating through the COO⁻, NH2 and Npeptide groups, whereas in Ph3Sn(HL) the ligand acts as a bidentate coordinating through the COO⁻ and NH2 groups. The ¹¹⁹Sn Mössbauer studies, together with the NMR data, indicate that, for the 1 : 1 monomeric derivatives, the polyhedron around tin in R2SnL is a trigonal bipyramid with the butyl groups and Npeptide in the equatorial positions, while the axial positions are occupied by a carboxylic oxygen and the amino nitrogen atom. In Ph3Sn(HL) the structure is intermediate between pseudotetrahedral and cis-trigonal bipyramidal, with the Namino and two phenyl groups in the equatorial plane and the carboxylate oxygen and the third phenyl group in axial positions. All the complexes have been screened against seven cancer cell lines of human origin, viz. MCF-7, EVSA-T, WiDr, IGROV, M19, MEL A498 and H226. Ph3Sn(HL) displays the lowest ID50 values of the tin compounds tested and reported in this paper. Its activity is comparable to those of methotrexate and 5-fluorouracil. All the di-n-butyltin compounds exhibit lower in vitro anti-tumour activities than Ph3Sn(HL); however, they do provide significantly better activities than etoposide and cis-platin. Copyright © 2003 John Wiley & Sons, Ltd.

The reaction of the 2,2-bis(organodichlorostannyl)propane [(Me3Si)2CH(Cl2)Sn]2CMe2 (A) with the corresponding organotin oxide {[(Me3Si)2CH(O)Sn]2CMe2}2 (B) does not provide the corresponding normally expected tetraorganodistannoxane {[(Me3Si)2CH(Cl)SnCMe2Sn(Cl)CH(SiMe3)2]O}n but a complex reaction mixture. One major product, namely the 2,4,6,8-tetraorgano-2,6-dichloro-1,5,9-trioxa-2,4,6,8-tetrastannabicyclo[3.3.1]nonane derivative [(Me3Si)2CHSnCMe2Sn(Cl)CH(SiMe3)2]2O3 (C) was identified in situ by 2D ¹H&bond;¹¹⁹Sn and ¹H&bond;¹³C heteronuclear multiple quantum coherence and heteronuclear multiple bond correlation NMR spectroscopy as well as electrospray mass spectrometry. Compound C is proposed to be in equilibrium with an ionic species C', the cation of which has an adamantane-type structure. Copyright © 2003 John Wiley & Sons, Ltd.

DFT calculations are reported for a series of tin- and crown-ether-based host compounds {i.e., the trimethyl derivatives [18]-crown-6-C6H3COOSn(CH3)3 and [15]-crown-5-C6H3COOSn(CH3)3} capable of binding cations and anions simultaneously. The B3LYP functional together with the 6-31G* basis set was used for the atoms C, H, N, O, S, Na and K and the 3-21G* basis set for Sn in order to obtain insights into the factors determining the nature of the interactions of these compounds with the neutral molecules acetone and H2O, the SCN⁻ anion, and the Na⁺ and K⁺ cations. The interaction strength pattern with these molecules was explained by the use of a series of reactivity descriptors such as the Fukui function, hardness, local softness, and the MEP (molecular electrostatic potential). In all cases studied in this paper, the complexes with Na⁺ were more stable than those with K⁺, correlating with the size of the cation and the volume available in the crown ether. Moreover, this finding is also in accordance with the greater hardness of Na⁺ relative to K⁺, in combination with the hard environment of the crown ether moiety. This region was also analysed by computation of electrostatic potentials, which showed that highly negative values are associated with the inside region of the cavity of the crown, this region thus being amenable to electrophilic attack. The HSAB principle, characterising the reactive sites on the basis of local softness and the Fukui function, provided a firm explanation of the reactivity of the tin atom of the crown ether benzocarboxylate towards SCN⁻, acetone and water. The HSAB concept was also successfully used to explain the preference of the tin atoms in both crown ethers to bind with the nitrogen atom rather than the sulfur atom of SCN⁻. This result is a confirmation that the tin atoms in the compounds under consideration behave as hard atoms. Overall, these results fit remarkably well with previous experimentally measured NMR spectroscopy data and demonstrate that the interactions of this kind of molecules can be predicted and interpreted by the use of DFT calculations and DFT-based reactivity descriptors, as well as MEP calculations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The reaction of di-tert-butyltin oxide with racemic 1,2,4-butane triol, aiming at synthesizing a model compound mimicking the tetra-tert-butyldistannoxane derivative of erythromycine A, affords two novel compounds, 1 and 2. Compound 1, which cannot be isolated as a pure product, was characterized in situ in C6D6 solution by two-dimensional, multinuclear (¹H, ¹³C, ^119/117Sn) NMR and proven to exhibit the same structural organooxotin moiety as the tetra-tert-butyldistannoxane derivative of erythromycine A, with however the position of an exchangeable hydroxylic proton now being unambiguously defined. Compound 2, isolated as a crystalline product, was characterized by X-ray diffraction analysis as the RS-isomer of a dimer generated from two monomeric units of opposite chirality obtained from 1:1 condensation of di-tert-butyltin oxide with racemic 1,2,4-butane triol; the hydroxylic protons of the OH groups of its carbon atoms C(1) and C(2) have been eliminated, giving rise to a five-membered cyclic 1,3,2 dioxastannolane-like pattern, where the oxygen of carbon C(1) of the ligand complexes the tin atom of a neighboring molecule, resulting in a centrosymmetric Sn2O2 core; the hydroxylic proton of the OH group of carbon atom C(4) of the ligand forms an intramolecular hydrogen bridge with the oxygen atom of C(2). The C6D6 solution structure of compound 2 is identical to that of the crystalline state, even though evidence is found for 2 to exist in solution as a mixture of 2-RS and 2-RR/SS dimers.

Calculations of traditional wave function and DFT based reactivity descriptors are reported for the nanocluster [(RSn)₁₂O₁₄(OH)₆]2+ (R = CH₃) in order to get insight into the factors determining the exact nature of its interactions with anions or neutral nucleophiles (F−, Cl−, OH−, H₂O, acetone, DMSO). Two levels of calculation (Hartree–Fock and DFT) were used in this study, giving the opportunity to compare the performance of both aproaches. As a whole the HF and DFT results, despite some numerical differences, are qualitatively and in most cases quantitatively similar, since no interchanges in the sequences are found. Calculated charge distributions indicate that the hexacoordinated tin atoms are expected to be harder, the pentacoordinated ones softer. This result is confirmed by the condensed local softness and experimental observations provided by the literature (X-ray, 119Sn NMR), thereby matching predictions made on the basis of the HSAB principle. Molecular electrostatic potential (MEP) calculations further confirm this selectivity, indicating that nucleophiles will approach preferentially the macrocation around the poles rather than at the equator of the cage. Calculated stabilization energies indicate that the charged (F−, Cl− and OH−) and uncharged (DMSO, acetone and water) nucleophiles tested all interact preferentially with the cage pole region around the hexacoordinated tin atoms. This feature appears related to the electrostatic nature of the interaction for the charged nucleophiles and to the tendency, for all the nucleophiles, to form hydrogen bridges with the μ₂-OH moieties. The basicity of the three types of oxygen atoms [μ₂-OH, μ₃-O(I), μ₃-O(P)] present in [(RSn)₁₂O₁₄(OH)₆)]2+ has been addressed by protonation energy and MEP calculations, taking into account accessibility factors not represented by atomic charges. Summarizing, it turns out that the hardness/softness properties of tin atoms are modulated by their coordination; however, the sole consideration of these quantities is not sufficient to predict in all cases the strength and orientation of the interaction between various nucleophiles and the cluster, since electrostatic interactions and H-bonding play a major role.