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The exterior application of fire-retardant (FR) timber necessitates it to have high durability because of the possibility to be exposed to rainfall. In this study, water-leaching resistance of FR wood has been imparted by grafting phosphate and carbamate groups of the water-soluble FR additives ammonium dihydrogen phosphate (ADP)/urea onto the hydroxyl groups of wood polymers via vacuum-pressure impregnation, followed by drying/heating in hot air. A darker and more reddish wood surface was observed after the modification. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, solid-state 13C cross-polarization magic-angle-spinning nuclear magnetic resonance (13C CP-MAS NMR), and direct-excitation 31P MAS NMR suggested the formation of C–O–P covalent bonds and urethane chemical bridges. Scanning electron microscopy/energy-dispersive X-ray spectrometry suggested the diffusion of ADP/urea into the cell wall. The gas evolution analyzed by thermogravimetric analysis coupled with quadrupole mass spectrometry revealed a potential grafting reaction mechanism starting with the thermal decomposition of urea. Thermal behavior showed that the FR-modified wood lowered the main decomposition temperature and promoted the formation of char residues at elevated temperatures. The FR activity was preserved even after an extensive water-leaching test, confirmed by the limiting oxygen index (LOI) and cone calorimetry. The reduction of fire hazards was achieved through the increase of the LOI to above 80%, reduction of 30% of the peak heat release rate (pHRR2), reduction of smoke production, and a longer ignition time. The modulus of elasticity of FR-modified wood increased by 40% without significantly decreasing the modulus of rupture. Validerad;2023;Nivå 2;2023-04-21 (joosat);Funder: OP RDE (Grant no.CZ.02.1.01/0.0/0.0/16_019/0000803); CT WOOD, Luleå University of TechnologyLicens fulltext: CC BY License

Crystalline bismuth(III) dithiocarbamato-chlorido complexes [Bi{S2CN(C3H7)2}Cl2] (I) and [Bi{S2CN(iso-C4H9)2}2Cl] (II) were prepared and comparatively studied by (13C, 15N) CP-MAS NMR spectroscopy, IR spectroscopy, and X-ray diffraction (CIF files CCDC nos. 1971976 and 1971975, respectively). The dithiocarbamate ligands are typically coordinated in the S,S'-iso- (I) or aniso- (II) bidentate-terminal mode. In each of the compounds, neighboring molecules are connected through one or two μ2-Cl– ligands into zigzag-like polymer chains, in which the central atom has sixfold coordination: [BiS2Cl4] (I) or [BiS4Cl2] (II). The binding unit in the polymer chains of I is a four-membered [Bi–(μ-Cl)2–Bi] metallocycle in the butterfly conformation (the dihedral angle is 140.51(3)°). Therefore, stronger binding of heteroleptic molecules in polymer chains leads to a considerably shorter interatomic Bi–Bi distances in I (4.0904(4) A) than in II (4.8772(4) A). The thermal behavior of heteroleptic bismuth(III) complexes was studied by simultaneous thermal analysis with recording of TG and DSC curves. Although the major product of thermal transformations of I and II is Bi2S3, the microprobe method also identified the presence of reduced bismuth and BiCl3.

We report on syntheses, characterisation by nuclear magnetic resonance (NMR) spectroscopy, X‐ray diffraction (XRD) measurements, and density functional theory (DFT) calculations of electronic/molec ...

Boric acid is known to enhance the kinetics of CO2 absorption by some active aqueous solutions. However, the mechanism of interaction of boric acid with CO2 in the presence of active molecules is n...

New heteroleptic mercury(ii) complexes [Hg4(S2CNPr2)6(NO3)2] (1) and [Hg4(S2CNPr2)4Cl4] (2) were synthesized and characterized by single-crystal X-ray dif raction and 13C and 15N MAS NMR spectroscopy. In these complexes, the metal atoms are linked in pairs by bridging dipropyldithiocarbamate ligands (Pr2Dtc) to form tetranuclear cations and molecules. The further structural organization of compound 1 to the polymeric chains [Hg4(S2CNPr2)6(NO3)2]n occurs due to the linking of [Hg4(S2CNPr2)6]2+ cations by pairs of bridging nitrate groups. The formation of the supramolecular polymeric structure of 2 is determined by pairwise secondary Hg⋯Cl bonds between the cyclic [Hg4(S2CNPr2)4Cl4] molecules, in which the central eight-membered metallocycle [Hg4S4] adopts a distorted chair conformation. The thermal behavior of compounds 1 and 2 was studied by simultaneous thermal analysis.

The double ionic-polymer complex ([Au(S2CNPr2)2][AgCl2])n (1) was prepared as an individual fixation form of gold(III) from NaCl solutions with silver(I) dipropyldithiocarbamate and was characterized by single-crystal X-ray diffraction and 13C magic-angle spinning (MAS) NMR spectroscopy. The structure of 1 comprises two nonequivalent centrosymmetric complex cations [Au(S2CNPr2)2]+ (A and B) and the discrete linear anion [AgCl2]–. Gold(III) cations are linked by pairs of unsymmetrical secondary Au…S bonds to form linear supramolecular chains (…A…B…)n. Neighboring cations are additionally linked by [AgCl2]– anions via secondary Ag…S and Cl…S bonds, the anions being involved in the overall stabilization of the supramolecular structure. The cation–anion interactions lead to a distortion of the linear configuration of the [AgCl2]– anion. The character of thermolysis of 1 accompanied by quantitative regeneration of bound Au and Ag was established by simultaneous thermal analysis.

The dinuclear complex mercury(II) cyclopentamethylenedithiocarbamate (piperidine-1-carbodithioate) [Hg2{S2CN(CH2)5}4] was synthesized and its chemisorption activity toward a solution of AuCl3 in 2 M HCl was studied. The chemisorption of gold from the solution forms an ionic gold(III)‒mercury(II) dithiocarbamato-chlorido complex comprising three isomeric gold cations and an unsymmetrical hexachlorodimercurate anion. The structural organization and thermal behavior of the resulting compounds was studied.

Chemisorption synthesis on the basis of the binuclear compound [Bi2{S2CN(C3H7)2}6] (I) and preparative isolation of the ion-polymeric heteronuclear gold(III)-bismuth(III) complex ([Au{S2CN(C3H7)2}2 ...

Amorphous titanium phosphate ion-exchangers are often of a “mixed type”, i.e., they contain a mixture of –HPO4 and –H2PO4 active groups. Their synthesis requires careful handling to obtain the same ...

Crystalline polymeric thallium(I) morpholinedithiocarbamate [Tl2{S2CN(CH2)4O}2] n (I) and the heteronuclear ion–polymeric gold(III)–thalium(III) complex ([Au{S2CN(CH2)4O}2][TlCl4]) n (II) are preparatively isolated and characterized by X-ray diffraction analysis and 13C MAS NMR spectroscopy. According to the X-ray diffraction data, the main structural units of compounds I and II (CIF files CCDC 1548079 and 1548080) are presented by the binuclear centrosymmetric molecule [Tl2{S2CN(CH2)4O}2], noncentrosymmetric complex cation [Au{S2CN(CH2)4O{2]+, and isomeric complex anions [TlCl4]–. The formation of the three-dimensional polymeric structure (coordination number of Tl is 7), which is not characteristic of thallium(I) dithiocarbamates, is a consequence of the participation of the secondary Tl…O and Tl…S bonds of two types in the supramolecular self-organization of compound I. Nonequivalent secondary interactions of the first type join the binuclear molecules [Tl2{S2CN(CH2)4O}2] into polymer layers, which, in turn, form the three-dimensional polymeric framework due to the secondary bonds Tl…S. The revealed ability of freshly precipitated compound I to the chemisorption of gold(III) from solutions (2 M HCl) makes it possible to obtain heteronuclear supramolecular complex II as an individual form of binding. In the structure of the latter, the pairs of stronger secondary Au…S bonds join the gold(III) cations into dimers [Au2{S2CN(CH2)4O}4]2+ of the angular structure, the structural ordering of which is achieved in the cationcationic polymeric chain ([Au2{S2CN(CH2)4O}4]2+) n of the helical type involving the pairs of less strong Au…S bonds between the adjacent binuclear units. The distorted tetrahedral anions [TlCl4]– are localized between the polymeric chains. The study of the thermal behavior of compounds I and II by simultaneous thermal analysis makes it possible to establish the character of thermal transformations of the substances and to identify Tl2S (I), TlCl, and elemental gold (II) as thermolysis products.

We used 1 H pulsed field gradient nuclear magnetic resonance to study the self-diffusion of polyethylene glycol (PEG) with average molecular mass of 200 and ions in mixtures of PEG with imidazolium bis(mandelato)borate (BMB) and imidazolium bis(oxalato)borate ionic liquids (ILs). The IL was mixed with PEG in the concentration range of 0-100 wt%. Within the temperature range of 295 to 353 K, the diffusion coefficient of BMB is slower than that of the imidazolium cation. The diffusion coefficients of PEG, as well as the imidazolium cation and BMB anions, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state. Generally, increasing the concentration of PEG leads to an increase in the diffusion coefficients of PEG and both the ions and decreases their activation energy for diffusion. Nuclear magnetic resonance chemical shift alteration analysis showed that the presence of PEG changes the chemical shifts of both ions but in different directions. Impedance spectroscopy was used to measure the ionic conductivity of the ILs mixed with PEG. Copyright © 2017 John Wiley & Sons, Ltd.

The crystalline nickel(II) di-i-amyl) dithiophosphate (Dtph), [Ni{S2P(O-i-C5H11)2}2] (I) was isolated on a preparative scale and characterized by 13C, 31P MAS NMR, and X-ray diffraction (CIF file CCDC no. 1469369). The χ2-statistic diagrams were constructed from full 31P CP/MAS NMR spectra for calculating the 31P chemical shift anisotropy: δ aniso = δ zz –δ iso and the asymmetry parameter η = (δ yy –δ xx )/(δ zz –δ iso ). The key structural unit of I is the centrosymmetric [Ni{S2P(O-i-C5H11)2}2] molecule in which the nickel atom coordinates two Dtph ligands in the isobidentate fashion. In molecule I, each carbon, oxygen, and sulfur atom is statistically disordered over two sites with equal occupancies. However, the disorder does not affect nickel and phosphorus. These results were interpreted as the presence in I of two [Ni{S2P(O-i-C5H11)2}2] molecules rotated through 21.0(1)° (the angle between the [NiS4] chromophore planes) relative to each other around the bisecting P–Ni–P axis passing through both four-membered [NiS2P] rings. The two molecules occupy crystal lattice sites with equal probabilities. The thermal behavior of I was studied by simultaneous thermal analysis under argon. The course of the thermal destruction of the complex was established, nickel pyrophosphate (Ni2P2O7) was identified as the final product of thermal transformations.

The main purpose of this work was to investigate the potential of ionic liquids (ILs) in crystal engineering. We have employed ILs with different combinations of cations and anions to study their role in directing crystal structure formation of a nicotinamide (NIC) and oxalic acid (OXA) system. A new crystal form of NIC–OXA salt (2:1) was identified and characterized using standard solid state tools such as powder X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and Raman and infrared spectroscopy. The crystal structure of the 2:1 salt was elucidated using single-crystal X-ray diffraction. The NIC–OXA 2:1 salt form revealed a two-dimensional layered structure, while the known 1:1 salt had a perpendicular “tape-like” structure. The 2:1 salt form could only be crystallized from the ILs possessing hydrogen bond acceptor functionality. We demonstrated that specific ILs could be selected as solvents for altering the solid-state structure of organic and inorganic materials.

It is demonstrated that a phosphonium orthoborate ionic liquid may serve as a wear reducing additive in biodegradable oils at steel-steel surfaces in the boundary lubrication regime. Tribological tests were performed in a ball-on-three plate configuration. A set of surface characterization techniques—SEM/EDS, FIB and white light interferometry were used to characterize surfaces following the tribotests and to observe the formation of any tribofilms. 11B NMR was used to follow changes in the composition of the ionic-liquid-oil blends and to identify boron-containing decomposition products after the tribotests. The ionic liquid reduces the wear of steel surfaces by up to 92% compared to the neat oil at 90°C; it is shown that the reduction in wear can be correlated with the formation of boron enriched patches in the boundary films.

1 H NMR pulsed field gradient was used to study self-diffusion of a phosphonium bis(salicylato)borate ionic liquid ([P 6,6,6,14 ][BScB]) in the pores of Vycor porous glass at 296 K. Confinement in pores increases diffusion coefficients of the ions by a factor of 35. However, some [P 6,6,6,14 ][BScB] ions demonstrated apparent diffusion coefficients much lower than their mean values, which may be due to partially restricted diffusion of the ions. We suggest that this fraction corresponds to areas where ions are confined by pore ‘necks’ (micropores) and empty voids. Heating of the ionic liquid/Vycor system at 330 K led to a change in the diffusivity of the ions, because of their redistribution in the pores. The size of the bounded regions is on the order of 1 μm, as estimated from the dependence of the ion diffusivity on the diffusion time.

Natural abundance solid-state multinuclear (13 C, 15 N and 29 Si) cross-polarization magic-angle-spinning NMR was used to study structures of three block copolymers based on polyamide and dimethylsiloxane and two polyamides, one of which including ferrocene in its structure. Assignment of most of the resonance lines in 13 C, 15 N and 29 Si cross-polarization magic-angle-spinning NMR spectra were suggested. A comparative analysis of 13 C isotropic chemical shifts of polyamides with and without ferrocene has revealed a systematic shift towards higher δ -values (de-shielding) explained as the incorporation of paramagnetic ferrocene into the polyamide backbone. In addition, the 13 C NMR resonance lines for ferrocene-based polyamide were significantly broadened, because of paramagnetic effects from ferrocene incorporated in the structure of this polyamide polymer. Single resonance lines with chemical shifts ranging from 88.1 to 91.5 ppm were observed for 15 N sites in all of studied polyamide samples. 29 Si chemical shifts were found to be around -22.4 ppm in polydimethylsiloxane samples that falls in the range of chemical shifts for alkylsiloxane compounds. The CO2 capture performance of polyamide-dimethylsiloxane-based block copolymers was measured as a function of temperature and pressure. The data revealed that these polymeric materials have potential to uptake CO2 (up to 9.6 cm3 g-1 ) at ambient pressures and in the temperature interval 30-40 °C. Copyright © 2016 John Wiley & Sons, Ltd.

We used H-1 nuclear magnetic resonance pulsed-field gradient to study the self-diffusion of polyethylene glycol (PEG) and ions in a mixture of PEG and imidazolium bis(mandelato)borate ionic liquids (ILs) at IL concentrations from 0 to 10 wt% and temperatures from 295 to 370 K. PEG behaves as a solvent for these ILs, allowing observation of separate lines in H-1 NMR spectra assigned to the cation and anion as well as to PEG. The diffusion coefficients of PEG, as well as the imidazolium cation and bis(mandelato) borate (BMB) anion, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state, while the lifetimes of the associated states of the ions and ions with PEG are less than similar to 30ms. Generally, increasing the concentration of the IL leads to a decrease in the diffusion coefficients of PEG and both ions. The diffusion coefficient of the anion is less than that of the cation; the molecular mass dependence of diffusion of ions can be described by the Stokes-Einstein model. NMR chemical shift alteration analysis showed that the presence of PEG changes mainly the chemical shifts of protons belonging to imidazole ring of the cation, while chemical shifts of protons of anions and PEG remain unchanged. This demonstrated that the imidazolium cation interacts mainly with PEG, which most probably occurs through the oxygen of PEG and the imidazole ring. The BMB anion does not strongly interact with PEG, but it may be indirectly affected by PEG through interaction with the cation, which directly interacts with PEG. Copyright (C) 2015 John Wiley & Sons, Ltd.

Oligomeric and protofibrillar aggregates formed by the amyloid-β peptide (Aβ) are believed to be involved in the pathology of Alzheimer's disease. Central to Alzheimer pathology is also the fact that the longer Aβ42 peptide is more prone to aggregation than the more prevalent Aβ40 . Detailed structural studies of Aβ oligomers and protofibrils have been impeded by aggregate heterogeneity and instability. We previously engineered a variant of Aβ that forms stable protofibrils and here we use solid-state NMR spectroscopy and molecular modeling to derive a structural model of these. NMR data are consistent with packing of residues 16 to 42 of Aβ protomers into hexameric barrel-like oligomers within the protofibril. The core of the oligomers consists of all residues of the central and C-terminal hydrophobic regions of Aβ, and hairpin loops extend from the core. The model accounts for why Aβ42 forms oligomers and protofibrils more easily than Aβ40 .

This work reports on the synthesis and physicochemical characterisation of novel halogen-free boron containing ionic liquids (hf-BILs) with dialkylpyrrolidinium cations [CnC1Pyrr]+, n = 4–14, and bis(mandelato)borate anion [BMB]−. All the synthesised compounds are liquids at room temperature. It was found that the thermal properties and density of these hf-BILs are affected by the length of the longest alkyl chain connected to the nitrogen atom in the pyrrolidinium cations. Differential scanning calorimetry measurements revealed that glass transition temperatures of these ionic liquids are in the temperature range from 218 to 241 K. Interestingly, the glass transition temperatures follow the “odd–even” effect related to the number of carbons (n) in one of the alkyl chains of [CnC1Pyrr]+. It was also found that hf-BILs' density decreases with an increase in the alkyl chain length of [CnC1Pyrr]+. It is suggested that the “odd–even” effect is associated with the difference in packing and specific interactions of cations and anions of this class of hf-BILs. Their lubricating properties, as 3 wt% additives in polyethylene glycol (PEG), were evaluated in steel–steel contacts. PEG with hf-BILs additive provided significantly lower wear and friction compared to the neat PEG and 5W40 engine oil. It was found that shortening the length of the longest alkyl chain in the cations of [CnC1Pyrr][BMB] significantly reduces frictional losses. Antiwear properties of [CnC1Pyrr][BMB] in PEG follow the same trend.

Polyanion-coated lipid vesicles are proposed to have an appreciable potential for drug delivery because of their ability to control the permeability of lipid bilayers by environmental parameters such as pH and temperature. However, details of the interaction of this class of polymers with lipids and their mechanisms of induced permeability are still being debated. In this work, we applied 1H NOESY to study details of the interaction of polyacrylic acid (PAA) fractions of molecular weights 5 and 240 kDa with dimyristoylphosphatidylcholine vesicles. We showed that PAA of two different molecular masses modifies lipid bilayers increasing disorder and probability of close contact between polar and hydrophobic groups. PAA molecules adsorb near the interface of lipid bilayers but do not penetrate into the hydrophobic core of the bilayer and, thus, cannot participate in formation of transbilayer channels, proposed in earlier works. Increasing the molecular mass of PAA from 5 kDa to 240 kDa does not change the effect of PAA on the bilayer, although PAA240 forms a more compact structure (either intra-molecular or inter-molecular) and interacts more strongly with interface lipid protons.

The structure and dynamic properties of micellar solutions of nonionic surfactants of a series of isononylphenol ethoxylates, C9H19C6H4O(C2H4O)nH (where n=6,8,9,10, and 12), were studied by NMR diffusometry, dynamic light scattering, and viscosimetry. The sizes of the micelles were determined for different surfactants and at different surfactant concentrations. The numbers of water molecules bound by a micelle and by one oxyethylene group of the surfactant were estimated.

The spatial structure of an active fragment of beta-amyloid Aβ1–40 heptapeptide Aβ16–22 (Lys-Leu-Val-Phe-Phe-Ala-Glu) in aqueous buffer solution and in complex with sodium dodecyl sulfate micelles as a model membrane system was investigated by 1H NMR spectroscopy and two-dimensional NMR (TOCSY, HSQC-HECADE (Heteronuclear Couplings from ASSCI-domain experiments with E.COSY-type crosspeaks), NOESY) spectroscopy. Complex formation was confirmed by the chemical shift changes of the heptapeptide's 1H NMR spectra, as well as by the signs and values of the NOE effects in different environments. We compared the spatial structure of the heptapeptide in borate buffer solution and in complex with a model of the cell surface membrane. Copyright © 2012 John Wiley & Sons, Ltd.

The paper deals with reactions of freshly precipitated diisopropyl dithiophosphate (Dtph) complexes of nickel(II), [Ni{S2P(O-iso-C3H7)2}2] and cadmium, [Cd2{S2P(O-iso-C3H7)2}4], with the [AuCl4]− in 2M HCl, resulting in gold transition from the solution to the precipitate as polymeric gold(I) diisopropyl dithiophosphate. The reduction of gold(III) to gold(I) noted in both cases is due to oxidation of the relevant part of the Dtph group to bis(O,O′-di-(iso)-propoxythiophosphoryl) disulfide, (iso-C3H7O)2P(S)S-S(S)P(O-iso-C3H7)2. The polynuclear gold(I) complex [Au2{S2P(O-iso-C3H7)2}2] n (I) was isolated on a preparative scale from the chemisorption system and studied by MAS 31P NMR and X-ray diffraction. The key structural unit of I is the non-centrosymmetric binuclear molecule [Au2{S2P(O-iso-C3H7)2}2] in which the gold atoms are connected by two bridging Dtph groups. The structure contains two types of non-equivalent binuclear molecules related as conformational isomers. Owing to the relatively weak Au-Au contacts, the neighboring binuclear [Au2{S2P(O-iso-C3H7)2}2] molecules are involved in an infinite polymeric chain with conformer alternation along the chain. To elucidate the conditions for the recovery of bound gold(I), the precipitates formed in the sorption systems were studied by simultaneous thermal analysis under argon. As the final product, thermolysis gives reduced metallic gold. The ability of dithiophosphate complexes to bind gold from a solution is much lower than that of dithiocarbamate complexes, which is due to oxidation of some Dtph groups to disulfide.

An NMR crystallography approach that combines experimental solid-state magic-angle-spinning (MAS) NMR with calculation is applied to the gamma polymorph of the pharmaceutical molecule, indomethacin. First-principles calculations (GIPAW) for the full crystal structure and an isolated molecule show changes in the (1)H chemical shift for specific aliphatic and aromatic protons of over -1 ppm that are due to intermolecular CH-pi interactions. For the OH proton, (1)H double-quantum (DQ) CRAMPS (combined rotation and multiple-pulse spectroscopy) spectra reveal intermolecular H-H proximities to the OH proton of the carboxylic acid dimer as well as to specific aromatic CH protons. The enhanced resolution in (1)H DQ-(13)C spectra, recorded at 850 MHz, enables separate (1)H DQ build-up curves (as a function of the DQ recoupling time) to be extracted for the aromatic CH protons. Supported by eight-spin density-matrix simulations, it is shown how the relative maximum intensities and rates of build-up provide quantitative insight into intramolecular and intermolecular H-H proximities that characterize the crystal packing.

Sizes of micelles and compositions of aggregates in the aqueous solutions of the nonionic surfactant oxyethylated monoalkyl phenol (neonol AF9-10) were determined by NMR spectroscopy, NMR diffusometry and dynamic light scattering in a wide range of tem- peratures near the cloud point. The cloud point extraction of phenol from aqueous solutions by the surfactant AF9-10 was performed.

By dropwise adding thio ligands to concentrated aqueous solutions of Cd(ClO4)(2).6H(2)O, Polymeric complexes, Cd(II) O, O'-dipropyl- dithiophosphate (1), O, O'-dibutyl-dithiophosphate (2), O, O'- d ...

Ultrasound sonication of protein and peptide solutions is routinely used in biochemical, biophysical, pharmaceutical and medical sciences to facilitate and accelerate dissolution of macromolecules in both aqueous and organic solvents. However, the impact of ultrasound waves on folding/unfolding of treated proteins, in particular, on aggregation kinetics of amyloidogenic peptides and proteins is not understood. In this work, effects of ultrasound sonication on the misfolding and aggregation behavior of the Alzheimer's A beta((1-40))-peptide is studied by pulsed-field gradient (PFG) spin-echo diffusion NMR and UV circular dichroism (CD) spectroscopy. Upon simple dissolution of A beta((1-40)) in perdeuterated trifluoroethanol, CF3-CD2-OD (TFE-d(3)), the peptide is present in the solution as a stable monomer adopting alpha-helical secondary structural motifs. The self-diffusion coefficient of A beta((1-40)) monomers in TFE-d(3) was measured as 1.35 x 10(-10) m(2) s(-1), reflecting its monomeric character. However, upon ultrasonic sonication for less than 5 min, considerable populations of A beta molecules (ca 40%) form large aggregates as reflected in diffusion coefficients smaller than 4.0 x 10(-13) m(2) s(-1). Sonication for longer times (up to 40 min in total) effectively reduces the fraction of these aggregates in H-1 PFG NMR spectra to ca 25%. Additionally, absorption below 230 nm increased significantly upon sonication treatment, an observation, which also clearly confirms the ongoing aggregation process of A beta((1-40)) in TFE-d(3). Surprisingly, upon ultrasound sonication only small changes in the peptide secondary structure were detected by CD: the peptide molecules mainly adopt alpha-helical motifs in both monomers and aggregates formed upon sonication. Copyright (C) 2010 John Wiley & Sons, Ltd.

Correction for ‘Revisiting syntheses of Ti(iv)/H2PO4–HPO4 functional ion-exchangers, properties and features’ by Mylène Trublet et al., New J. Chem., 2017, DOI: 10.1039/c7nj03065g.

Platinum(II) O,O′-dicyclohexyl dithiophosphate [Pt{S2P(O-cyclo-C6H11)2}2] (I) and platinum(II) O,O′-diisopropyl dithiophosphate [Pt{S2P(O-iso-C3H7)2}2] (II) complexes were obtained and studied by solidstate 13C, 31P, and 195Pt CP/MAS NMR spectroscopy. The dithiophosphate (Dtph) ligands in molecular structure I were found to be coordinated by platinum in S,S′-bidentate fashion to form the planar chromophore [PtS4] (single-crystal X-ray diffraction data). For complex II, a new α-form (α-II) was obtained and identified by 31P MAS NMR spectroscopy. The 31P chemical shift anisotropy δaniso and the asymmetry parameter η of the 31P chemical shift tensor were calculated from the whole MAS spectra.

The structures and spectroscopic properties of mononuclear and binuclear mercury(II) and copper(II) complexes with four dithiocarbamate ligands R2NC(S)S− (R = CH3, C2H5, or iso-C3H7; R2 = (CH2)6) were studied by solid-state 13C and 15N CP/MAS NMR and EPR spectroscopy. Mercury(II) N,N-cyclohexamethylenedithiocarbamate [Hg2{S2CN(CH2)6}4] was obtained and characterized in detail by X-ray diffraction analysis at 299 K. The binuclear molecule of the complex is centrosymmetric; the central tricyclic fragment [Hg2S4C2] is in the chair conformation. In the 13C and 15N NMR spectra, the signals were assigned to the dithiocarbamate ligands with different structural functions: bidentate chelating and combined (both chelating and bridging) ones. The differences between the isotropic 15N chemical shifts for the dialkyldithiocarbamate ligands were interpreted in terms of combination of the mesomeric effect of the =NC(S)S-groups and the inductive effect of the alkyl substituents. According to the EPR data, copper(II) in magnetically diluted systems is mainly found in heterobinuclear molecules [CuHg(S2CNR2)4] and the geometry of the chromophores [CuS5] approximates to a tetragonal pyramid.

Silver(I) complexes with four symmetrically substituted O,O′-dialkyl derivatives of dithiophosphoric acid of the general formula [Ag{S2P(OR)2}] n (R = C2H5, i-C3H7, C4H9, and s-C4H9) were obtained. ...

A number of polycrystalline copper(I) O,O'-dialkyldithiophosphate cluster compounds with Cu-4, Cu-6, and Cu-8 cores were synthesized and characterized by using extended X-ray absorption fine-structure (EXAFS) spectroscopy. The structural relationship of these compounds is discussed. The polycrystalline copper(i) O,O'-diisobutyldithiophosphate cluster compounds, [Cu-8{S2P(OiBu)(2),}(6)(S)] and [CU6{S2P(OiBU)(2)}(6)], were also characterized by using P-31 CP/MAS NMR (CP = cross polarization, MAS = magic-angle spinning) and static Cu-65 NMR spectroscopies (at different magnetic fields) and powder X-ray diffraction (XRD) analysis. Comparative analyses of the P-31 chemical-shift tensor, and the Cu-65 chemical shift and quadrupolar-splitting parameters, estimated from the experimental NMR spectra of the polycrystalline copper(I) cluster compounds, are presented. The adsorption mechanism of the potassium O,O'-diisobutyldithiophosphate collector, K[S2P(OiBu)(2)], at the surface of synthetic chalcocite (Cu2S) was studied by means of solid-state P-31 CP/MAS NMR spectroscopy and scanning electron microscopy (SEM). P-31 NMR resonance lines from collector-treated chalcocite surfaces were assigned to a mixture of [Cu-8{S2P(OiBu)(2)}(6)(S)] and [Cu-6- {S2P(OiBu)(2)}(6)] compounds.

A comparative study of polynuclear thallium complexes with dialkyldithiocarbamates [Tl2{S2CNR2}2]n (R = CH3, i-C3H7, C4H9, and i-C4H9; R2 = (CH2)6) was performed by solid-state 13C and 15N CP/MAS NMR spectroscopy. The dithiocarbamate groups were found to be structurally equivalent in the complexes studied. An increase in the positive inductive effect of alkyl substituents at the N atom increased 15N chemical shifts as a result of a combination of positive inductive effect of the alkyl substituents and the mesomeric effect of=NC(S)S-groups. The first representative of thallium(I) complexes with a cyclic dithiocarbamate ligand [Tl2{S2CN(CH2)6}2]n was obtained. Its molecular structure was determined from X-ray diffraction data. The β-form of the isotope-substituted complex [63/65CuTl2{S2CN(CH2)6}4] was obtained and examined by EPR spectroscopy. The EPR spectra were modeled at the second order of the perturbation theory. The spin density at the thallium atoms was calculated and its distribution over the AOs of thallium was determined.

A multi-step procedure for the preparation of meso/macroporous AlPO-5 spherical macrostructures using cation exchange resin beads as macrotemplates is presented. Firstly, aluminum species were intr ...

Different potassium salts and zinc(II) and nickel(II) O,O'-dialkyldithiophosphate complexes were studied by solid-state 31P CP/MAS and static NMR and ab initio quantum mechanical calculations. Spectra were obtained at different spinning frequencies, and the intensities of the spinning sidebands were used to estimate the chemical shift anisotropy parameters. Useful correlations between the shapes of the 31P chemical shift tensor and the type of ligand were found: terminal ligands have negative values of the skew kappa, while bridging and ionic ligands have positive values for this parameter. The experimental results were compared with known X-ray diffraction structures for some of these complexes as well as with ab initio quantum mechanical calculations, and a useful correlation between the delta22 component of the 31P chemical shift tensor and the S-P-S bond angle in the O,O'-dialkyldithiophoshate zinc(II) and nickel(II) complexes was found: delta22 increases more than 50 ppm with the increase of S-P-S bond angle from ca. 100 degrees to 120 degrees , while the other two principal values of the tensor, delta11 and delta33, are almost conserved. This eventually leads to the change in sign for kappa in the bridging type of ligand, which generally has a larger S-P-S bond angle than the terminally bound O,O'-dialkyldithiophosphate group forming chelating four-membered P(ss)Me heterocycles.

Crystalline thallium(I) alkylxanthate complexes [Tl{S(S)COR}]n (R = C2H5, i-C3H7, i-C4H9, s-C4H9, and C5H11) and isotope-substituted heteropolynuclear Cu(II)Tl(I) complexes [63(65)CuTl6(S2COR)8] (R= i-C4H9 and C5H11) were obtained and studied by ESR and high-resolution solid-state 13C CP/MAS NMR spectroscopy. According to the 13C NMR data, polynuclear thallium(I) complexes contain structurally equivalent alkylxanthate ligands. The ESR study revealed the Jahn-Teller dynamic effect in Cu(II)Tl(I) complexes; the nuclei of six Tl atoms are involved in the hyperfine interaction.

The effects of five fragments of prostatic acid phosphatase on dimyristoylphosphatidylcholine lipid multi-lamellar liposomes were studied by 2H and 31P NMR spectroscopy and those on planar supported multi-bilayers of the same lipid, by 1H and 31P NMR spectro-scopy. It was found that hydrophobic interaction is a dominated factor of the peptide–membrane binding, while the short α-helical fragments PAP(262-270) and PAP(262-272) strongly interact with the membrane at the interface, generally following to the Gibbs free energy of water-to-interface insertion.

The effect of added Alzheimer's Aβ(1-40) peptide of the wild type on the lateral diffusion of lipids in macroscopically oriented bilayers of ‘raft’ compositions [a mixture of dioleoylphosphatidylcholine (DOPC), sphingomyelin (SM) and cholesterol (CHOL)] was studied by an NMR-diffusion technique. In homogeneous bilayers, diffusion coefficients decrease, while they change differently in liquid ordered and in liquid disordered phases at varied concentrations of CHOL; this was explained by the decreased maximum solubility of CHOL in phospholipids in the presence of Aβ(1-40) peptide.

Alkylxanthate complexes of the general formula [M{S(S)COR}2] (M = Ni, 63Cu, and 65Cu; R = C2H5, i-C3H7, i-C4H9, s-C4H9, and C5H11) were synthesized and studied by EPR and high-resolution solid-state 13C CP/MAS NMR. In the copper(II) complexes stabilized in the matrix of nickel(II) compounds, square planar chromophores [CuS4] are characterized by rhombic distortion (EPR data). Experimental EPR spectra were simulated at the second order of perturbation theory. Nickel(II) complexes were characterized by 13C NMR spectra. In all cases, the –OC(S)S– groups were found to exhibit intramolecular structural equivalence.

Aggregation cascade for Alzheimer's amyloid-beta peptides, its relevance to neurotoxicity in the course of Alzheimer's disease and experimental methods useful for these studies are discussed. Details of the solid-phase peptide synthesis and sample preparation procedures for Alzheimer's beta-amyloid fibrils are given. Recent progress in obtaining structural constraints on Abeta-fibrils from solid-state NMR and scanning transmission electron microscopy (STEM) data is discussed. Polymorphism of amyloid fibrils and oligomers of the 'Arctic' mutant of Abeta(1-40) was studied by (1)H,(13)C solid-state NMR, transmission electron microscopy (TEM) and atomic force microscopy (AFM), and a real-time aggregation of different polymorphs of the peptide was observed with the aid of in situ AFM. Recent results on binding of Cu(II) ions and Al-citrate and Al-ATP complexes to amyloid fibrils, as studied by electron paramagnetic resonance (EPR) and solid-state (27)Al NMR techniques, are also presented.

Lateral diffusion in dimyristoylphosphatidylcholine lipid bilayers decreases in the presence of cholesterol and curcumin, as measured by 1 H NMR spectroscopy, but the mechanisms of action of these two compounds are different.

High-resolution 13C and 15N solid-state NMR spectra were recorded for seven crystalline tetraalkyl-thiuram disulfides and their cyclic analogs of the general formula [R2NC(S)S]2 (where R = CH3, C2H5, C3H7, and i-C3H7 or R2 = (CH2)5, (CH2)6, and (CH2)4O). The 15N and 13C NMR resonances were assigned to the particular atoms in the compounds studied. Different isotropic 15N chemical shifts for both dialkyldithiocarbamato groups were interpreted while considering the inductive effects of the alkyl substituents combined with the mesomeric effect of the dithiocarbamato group. X-ray diffraction data were used to refine the molecular structure of bis(cyclohexamethylene)thiuram disulfide and to quantitatively characterize the conformations of the seven-membered N(CH2)6 heterocycles.

We present a (31)P NMR spectroscopy study of planar glass-plate-oriented multi-bilayers of dimyristoylphosphatidylcholine (DMPC) with addition of polyethylene oxide (PEO). This work revealed the presence of a new component in the spectra that appeared only with addition of a small fraction of PEO (up to one PEO segment per dimyristoylphosphatidylcholine molecule) and disappeared when larger amounts of PEO were added. We explained this phenomenon as an effect of an inhomogeneous force field induced by the PEO molecules located at a certain depth in the lipid membrane interface region.

Two-dimensional (1)H double-quantum and (14)N-(1)H(1)H-(13)C heteronuclear magic-angle spinning (MAS) NMR spectra recorded at natural isotopic abundance identify specific intermolecular COOH···N(arom) and CH(arom)···O=C hydrogen-bonding interactions in the solid-state structure of an indomethacin-nicotinamide cocrystal, thus additionally proving cocrystal formation.

We report a symmetrical sequence of 5 pi pulses for total sideband suppression in magic-angle-spinning NMR. The sequence is almost evenly spaced and shorter than previous 4 and 6 pi pulse methods.

The thermal behaviour, molecular orientation and lateral diffusion in the bilayered systems of dimyristoylphosphatidylcholine (DMPC) in the presence of poly(ethylene oxide) (PEO) were studied by NMR and DSC techniques, and it was found that PEO decreases the melting temperature (of vesicles and flat multibilayers) and affects the degree of orientation of DMPC molecules relative to the bilayer normal, but it does not influence the lateral diffusion of DMPC molecules.

Five halogen-free orthoborate salts comprised of three different cations (cholinium, pyrrolidinium and imidazolium) and two orthoborate anions, bis(mandelato)borate and bis(salicylato)borate, were synthesised and characterised by DSC, X-ray diffraction and NMR. DSC measurements revealed that glass transition points of these orthoborate salts are in the temperature range from −18 to −2 °C. In addition, it was found that [EMPy][BScB] and [EMIm][BScB] salts have solid–solid phase transitions below their melting points, i.e. they exhibit typical features of plastic crystals. Salts of the bis(salicylato)borate anion [BScB]− have higher melting points compared with corresponding salts of the bis(mandelato)borate anion [BMB]−. Single crystal X-ray diffraction crystallography (for [Chol][BScB] crystals) and solid-state multinuclear (13C, 11B and 15N) NMR spectroscopy were employed for the structural characterisation of [Chol][BScB], [EMPy][BScB] and [EMIm][BScB], which are solids at room temperature: a strong interaction between [BScB]− anions and [Chol]+ cations was identified as (i) hydrogen bonding between OH of [Chol]+ and carbonyl groups of [BScB]− and (ii) as the inductive C–H⋯π interaction. In the other salt, [EMIm][BScB], anions exhibit π⋯π stacking in combination with C–H⋯π interactions with [EMIm]+ cations. These interactions were not identified in [EMPy][BScB] probably because of the lack of aromaticity in cations of the latter system. Our data on the formation of a lanthanum complex with bis(salicylato)borate in the liquid mixture of La3+(aq) with [Chol][BScB] suggest that this class of novel ILs can be potentially used in the extraction processes of metal ions of rare earth elements.

We demonstrate the ability of multidimensional Laplace NMR (LNMR), comprising relaxation and diffusion experiments, to reveal essential information about microscopic phase structures and dynamics of ionic liquids that is not observable using conventional NMR spectroscopy or other techniques.