The solid-state organization of 'self-doped' PPV oligomers.

Using a combination of multi-frequency EPR and NMR spectroscopy and quantum-chemical calculations at the level of Density Functional Theory (DFT), the organization of self-doped PPV oligomers in their solid state is investigated. The analysis of the different spectra shows that the electrochemical procedure used to self-dope these materials produces positive radicals (polarons) in an almost quantitative way, but still magnetically isolated polarons are observed. The difference between chemical and electrochemical oxidation of the oligomers is studied in detail.

Trilacunary A-beta-Keggin tungstogermanates and -silicates functionalized with phenyltin(IV) electrophiles.

The first organic derivative of a beta-Keggin tungstogermanate, the monomeric Keggin anion [{(C(6)H(5))Sn(OH)}(3)(A-beta-GeW(9)O(34))](4-) (1), was the only species isolated from the reaction of (C(6)H(5))SnCl(3) with Na(10)[A-beta-GeW(9)O(34)] in water, whereas the Si-analogue [{(C(6)H(5))Sn(OH)}(3)(A-beta-SiW(9)O(34))](4-) (2) and two dimeric tungstosilicates, the unprecedented species [{(C(6)H(5))Sn(A-beta-H(3)SiW(9)Sn(2)O(37))}(2)O(2)](8-) (3) and the known sandwich-type polyanion [{(C(6)H(5))Sn(OH)}(3)(A-beta-H(3)SiW(9)O(34))(2)](8-) (4), were isolated starting from [A-beta-SiW(9)O(34)](10-). The novel polyanion 3 can be described as the product of a double Sn-C hydrolysis followed by condensation of two subunits of 2 through double Sn-O-Sn bridge formation. Solid-state characterization has been carried out by infrared spectroscopy, thermogravimetry and single-crystal X-ray diffraction, representing the first structural analysis for 4.

Phase behavior in blends of ethylene oxide-propylene oxide copolymer and poly(ether sulfone) studied by modulated-temperature DSC and NMR relaxometry.

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), T(2) NMR relaxometry, and light scattering. The apparent heat capacity signal in MTDSC is used for the characterization of polymer miscibility and morphology development. T(2) NMR 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.

Recipe for new diorganostannates, [R2Sn(OS(O)2R1)4]2-, bearing alkanesulfonate groups using dialkyl sulfite as the reagent.

A one-pot reaction between di-n-propyl/di-n-butyltin oxide, dialkyl sulfite, and triethylamine or tetra-n-alkylammonium iodide proceeds under ambient conditions (110-120 degrees C, 20 h) via sulfur-centered Arbuzov rearrangement to afford the corresponding dianionic tetraalkanesulfonato diorganostannates [R2Sn(OSO2Me)4].2Et3NMe [R = n-Pr (1), n-Bu (2)] as well as [n-Bu(2)Sn(OSO(2)R(1))(4)].(2)R(2)(4)N [R(1) = Me, Et, n-Pr; R(2) = Et (3, 5, and 7), n-Bu (4, 6, and 8)].

Characterization of titanium dioxide nanoparticles dispersed in organic ligand solutions by using a diffusion-ordered spectroscopy-based strategy.

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.

A doubly folded spacer in a self-assembled hybrid material.

The hydrolysis of a bridged alpha,omega-bis(trialkynylstannylated) compound leads to a hybrid material ordered by self-assembly where the spacer forms two six-membered [1,2]oxastanninane rings by intramolecular coordination.

Polystyrene-supported organotin dichloride as a recyclable catalyst in lactone ring-opening polymerization: assessment and catalysis monitoring by high-resolution magic-angle-spinning NMR spectroscopy.

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 epsilon-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 (n)J((1)H-(117/119)Sn) and (n)J((13)C-(117/119)Sn) coupling constants.

In situ evaluation of interfacial affinity in CeO2 based hybrid nanoparticles by pulsed field gradient NMR.

Complexation affinity of laurate ligands (C(12)H(23)O(2)) grafted onto the surface of cerium(IV) oxide nanoparticles can be probed and quantified in situ, by pulsed field gradient (1)H NMR through the dependence of the diffusion coefficient on the size of a species.

Alkylchlorotins grafted to cross-linked polystyrene beads by a -(CH2)n- spacer (n=4, 6, 11): selective, clean and recyclable catalysts for transesterification reactions.

Insoluble polystyrene grafted compounds of the type (P-H)(1-t){P-(CH2)n SnBu(p)Cl(3-p)}(t), (P-H)(1-t){P-(CH2)n SnBuO}(t) and (P-H)(1-t)[{P-(CH2)n SnBuCl}2O](t/2), in which (P-H) is a cross-linked polystyrene; n=4, 6, and 11; p=0 and 1; and t the 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.

Assessing weak intramolecular donor-acceptor interactions using 1H-117Sn J-HMQC spectroscopy.

It is demonstrated that long-range nJ(1H,117Sn) coupling constants down to 0.3 Hz, can be accurately quantified from non-linear fitting of the sine modulation of the associated 1H-117Sn correlation cross-peak intensities sampled as a function of the heteronuclear antiphase coherence preparation time in the 1H-117Sn J-HMQC pulse sequence. The contribution of additional, undesired modulations is illustrated and assessed using the product operator formalism, and is traced back to contributions that arise from miss-setting of the wandering 180 degrees pulse angle in the constant time period.

Delayed interconversion of D-glucose anomers in D2O.

The anomeric specificity of D-glucose metabolism and functional effects is currently assessed either over about 5 min at 37 degrees C or longer periods at much lower temperatures. In the present study, the half-life for the interconversion of D-glucose anomers at 30 degrees C was found to be increased (P<0.005) from 17.

Probing ionic association on metal oxide clusters by pulsed field gradient NMR spectroscopy: the example of Sn12-oxo clusters.

Pulsed field gradient (1)H NMR spectroscopy has been applied to investigate the association behavior of the Sn(12)-oxo cluster macrocation [(BuSn)(12)O(14)(OH)(6)](2+) with two different and smaller anions, p-toluenesulfonate (PTS(-)) and diphenylphosphinate (Ph(2)PO(2) (-)). 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 (1)H resonances available from each species, allows us to evidence the occurrence of ion exchange in such systems.

Mechanistic study of Bu2SnCl2-mediated ring-opening polymerization of epsilon-caprolactone by multinuclear NMR spectroscopy.

The ring-opening polymerization (ROP) of epsilon-caprolactone (CL) was carried out in toluene at 100 degrees C with n-propanol (nPrOH) in the presence of Bu(2)SnCl(2). 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 (alpha-propyloxy)(omega-hydroxy)poly(epsilon-caprolactone) chains. In order to gain fundamental understanding of the mechanistic factors governing the polyester chain growth, advanced (1)H, (13)C, and (119)Sn NMR investigations were performed in situ in [D(8)]toluene, as well as with model solutions that contained Bu(2)SnCl(2) and binary mixtures of the components at various concentrations and temperatures.

Fine-tuned characterization at the solid/solution interface of organotin compounds grafted onto cross-linked polystyrene by using high-resolution MAS NMR spectroscopy.

The structural characterization of organotin compounds that are grafted onto insoluble cross-linked polymers has necessarily been limited to elemental analysis, infrared spectroscopy, and in a few instances, solid-state NMR spectroscopy. This important bottleneck in the development of such grafted systems has been addressed by using high-resolution magic angle spinning (hr-MAS) NMR spectroscopy. The great potential of this technique is demonstrated through the structural characterization of diphenylbutyl-(3,4) and dichlorobutylstannanes (5,6), grafted onto divinylbenzene cross-linked polystyrene by means of a suitable linker (1, 2).

Reactions of [t-Bu(2)SnO](3) with [t-BuX(2)Si](2) (X = F, Cl). Syntheses and Structures of Novel Stannasiloxanes and of [(t-Bu(2)FSn)(2)O](2), the First Fluorine-Containing Tetraorganodistannoxane(,).

Di-tert-butyltin oxide, (t-Bu(2)SnO)(3) (1), reacts with 1,2-di-tert-butyltetrachlorodisilane, (t-BuCl(2)Si)(2) (2), to provide the stannasiloxane t-Bu(2)Sn[OSi(OSnCl-t-Bu(2))-t-Bu](2) (4, racemate). The reaction of 1 with 1,2-di-tert-butyltetrafluorodisilane, (t-BuF(2)Si)(2) (3), provides the stannasiloxane [t-Bu(F)SiOSn-t-Bu(2)](2)O (5, meso/racemate mixture) and the tetraorganodistannoxane [t-Bu(2)(F)SnOSn(F)-t-Bu(2)](2) (6). Under loss of (1)/(3) mole equiv of 1, the stannasiloxane 5 is transformed into t-Bu(2)Sn[OSi(F)-t-BuSi(F)-t-BuO](2)Sn-t-Bu(2) (7).

Synthesis and Solution State Characterization by Gradient-Enhanced 2D Multinuclear NMR Spectroscopy of a Fluorine-Bridged Dimethyltin(IV) Salicylaldoximate Derivative.

The reaction of [(Me(2)Sn)(2)(Me(2)SnO)(ONZOH)(HONZO)(ONZO)] (HONZOH = o-HON=CHC(6)H(4)OH, salicylaldoxime) with ammonium fluoride yields a fluorotris(dimethyltin) disalicylaldoximate complex, compound 4, containing one seven-coordinate and two five-coordinate tin atoms, with a fluoride anion bridging the five-coordinate tin atoms. Though 4 can be obtained in a crystalline form, its crystals are unsuitable for X-ray analysis. Its structure has been completely characterized in solution by 1D (1)H, (13)C, (119)Sn, and (19)F NMR spectra and 2D gradient-assisted (1)H-(119)Sn and (1)H-(13)C HMQC and HMBC NMR spectra.