Synthesis and spectroscopic characterisation of BODIPY based fluorescent off-on indicators with low affinity for calcium

Two fluorescent off-on Ca2+ indicators based on APTRA (o-aminophenol-N,N,O-triacetic acid) as low-affinity ligand for Ca2+ and BODIPY(4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) as a fluorophore were synthesized. The new BODIPY-APTRA compounds absorb in the visible spectrum, with absorption maxima from 505 nm to 570 nm, and have fluorescence spectra that span the visible spectrum, with emission maxima ranging from 525 nm to 625 nm dependent on the substituents at the alpha-positions to the nitrogen atoms. The indicators show a large increase of the fluorescence quantum yield upon increasing Ca2+ concentration. The ground-state dissociation constants Kd estimated at 20 degrees C in 100 mM KCl aqueous buffered solution, pH 7.20, for the two complexes with Ca2+ were found to be around 100 microM.     

Reduction of enedicarboxylate compounds with low valent titanium

The carbon—carbon double bonds of enedicarboxylate compounds can be reduced readily with TiCl₄LiAlH₄Et₃N in THF. Other double bond of the enedicarboxylate does not react during the reduction process.     

Synthesis and characterisation of a polymer-bound rhodium-benzimidazole complex as catalyst for the hydrogenation of nitroarenes

A polymer-anchored rhodium complex was synthesised by sequential attachment of benzimidazole (BzlH) and RhCl₃ to chloromethylated poly(styrene–divinylbenzene) co-polymer (PSDVB) with 6.5% cross-linking. The catalyst was characterised by X-ray photoelectron spectroscopy, far-IR, UV–Vis, FTIR, SEM and thermogravimetric analysis. Various physico-chemical properties such as bulk density, surface area and swelling behaviour in different solvents were also studied. The polymer-anchored complex was tested as a catalyst for reduction of nitroarenes, namely o,m,p-nitrobenzoic acid, nitroaniline, nitrophenol and nitrotoluene. Kinetic measurements were carried for o-nitroaniline and p-nitrophenol by varying temperature, catalyst concentration and concentration of substrates. The rate of the reaction was found to be first order with respect to catalyst concentration and also with substrate concentration at low concentrations, becoming independent of substrate at higher concentrations. A plausible mechanism for the reaction is proposed. The energy and entropy of activation calculated from Arrhenius plots indicate high activity of the catalyst on the support. The recycling efficiency of the catalyst has been studied and there was no leaching of metal from the catalyst surface.     

Deoxygenation of triphenylarsine oxide to triphenylarsine by low valent titanium

Low valent titanium was used to deoxygenate triphenylarsine oxide to triphenylarsine.     

Synthesis and characterisation of some new stabilisers for polyvinylchloride

Some new stabilisers having a chelating polymeric structure were synthesised and characterised, i.e., 8-hydroxyquinoline-formaldehyde chelating resins of Cd, Zn, and Pb. The efficiency of these new stabilisers was studied with respect to PVC. The stabilised PVC samples showed outstanding thermal stability as studied by thermogravimetric techniques, i.e., the percentage of HCl evolved reduced remarkably with increasing polymer decomposition temperature.     

Synthesis and characterisation of new ditopic receptors for guanosine

Novel ditopic receptors for guanosine have been prepared and characterised. Their association constants with a lipophilic guanosine derivative are somewhat smaller than the expected values for a guanosine-cytidine base pair, but remain in a useful range for building supramolecular structures.     

Recent developments in the chemistry of low valent Group 14 hydrides

This Perspective discusses the synthesis and reactivity of low valent Group 14 hydrides of germanium and tin. The use of hindered terphenyl ligands has facilitated the isolation of a number of unusual new main group hydride structural types (each predicted by computational work), and has culminated in the use of these species as precursors to new cluster archetypes.     

低价钨化合物反应的研究-结构组成及其与亚砜和N-氧化吡啶的还原反应

六氯化钨-正丁基锂(1)与六氯化钨-锌(2)能将亚砜还原为相应的硫醚,将N-氧化吡啶还原为吡啶,在合适的条件下,产率高于90%.分离了六氯化钨与正丁基锂在四氢呋喃中产生的低价钨化合物,运用物理分析方法(ESCA,IR,1H和13C NMR)测得其组成为WCl4(THF)n.     

Synthesis and characterisation of urethane-methacrylates I

The paper describes the synthesis of urethane methacrylate resins by reaction of tolylene diisocyanate (TDI), butanol-1 (B) and 2-hydroxyethylmethacrylate (HEMA) by a two step procedure. Characterisation was done using FT-IR, FT-NMR, Mass Spectroscopy. The effect of temperature on the UV-curing behaviour was investigated by differential photocalorimetry. An activation energy of 8.4 kJ/mole was found in the temperature range of 50–100°C. Free radical polymerisation in presence of benzoyl peroxide was also investigated. The polymers were stable upto 200°C in N₂ atmosphere. A two step decomposition was observed in the temperature range of 200–500°C.

---

Zusammenfassung Vorliegende Arbeit beschreibt die Synthese von Urethan-methacrylat-Harzen durch die Reaktion von Toluylendiisocyanat (TDI), Butanol-1 (B) und 2-Hydroxyethylmethacrylat (HEMA) in einem zweistufigen Herstellungsverfahren. Charakterisiert wurden die Produkte mittels FT-IR, FT-NMR und Massenspektroskopie. Anhand von Differentialfotokalorimetrie wurde der Einfluß der Temperatur auf das UV-Aushärtungsverhalten untersucht. Im Temperaturbereich 50–100°C wurde eine Aktivierungsenergie von 8.4 kJ/mol gefunden. Weiterhin wurde auch die Radikalkettenpolimerisation in Gegenwart von Benzoylperoxid untersucht. In Stickstoffatmosphäre sind die Polymere bis 200°C stabil. Im Temperaturbereich 200–500°C wurde eine zweistufige Zersetzung beobachtet.

---

---

The Instrument system of E. I. DuPont de Nemours & Co. is acknowledged for differential photocalorimeter studies.     

Synthesis and characterisation of branched polyarylethers

Polyarylethers (Polysulfone: PSU, Polyethersulfone: PES) belong to the group of high performance polymers, having high glass transition temperature as well as high continuous use temperature. As a consequence of their high glass transition temperature, these polymers display high melt viscosity, which limits the number of accessible applications. Since the conventional methods to improve the flow characteristics are limited, the influence of branching by incorporation of the tri-functional monomer 1,1,1-Tris-(4-hydroxyphenyl)ethane (THPE) on the flow and the mechanical performance of PES was studied. Branching enhances the flow of Polyethersulfone significantly, but has a deleterious effect on the toughness, especially Charpy impact and tensile elongation.     

Synthesis and characterisation of tetra-tetrazole macrocycles

The syntheses of tetra-tetrazole macrocycles, containing two bis-tetrazole units linked by a variety of alkyl-chain lengths from four to eight carbons, are described. The crystal structures of three of these derivatives are reported, and the molecular conformation in the solid state is compared to that of the previously reported tetra-tetrazole macrocycle and to other bis- and tris(tetrazole)benzene structures. The macrocycle conformation is influenced by the length of the alkyl-chain linker, the relative orientation of the tetrazole rings on the benzene ring and by intermolecular interactions. In the macrocycles based on 1,2-bis(tetrazole)benzene, the adjacent tetrazole rings on the benzene ring are prevented from becoming co-planar on intramolecular (steric) grounds. In the 1,3- and 1,4-bis(tetrazole)benzene derivatives, there is no such impediment, and a co-planar arrangement is observed where intra- and/or intermolecular stacking interactions exist. Deviations from co-planarity are associated with optimisation of intermolecular interactions between the tetrazole rings and adjacent alkyl chains. In the macrocycle based on 1,4-bis(tetrazole)benzene with four-carbon linkers, an intramolecular stacking interaction exists, which precludes the presence of any cavity. In the macrocycle based on 1,3-bis(tetrazole)benzene with six-carbon linkers, a cavity of 10.8×9.4 Å is observed for each molecule in the solid state, although the packing of adjacent molecules is such that there are no extended channels running through the crystal.     

Synthesis and characterisation of low density porous polymers by reversible addition-fragmentation chain transfer (RAFT)

PolyHIPE foams with densities of 0.05–0.1 g cm^?3 have been prepared by the polymerisation of the continuous phase of high internal phase emulsions (HIPEs). The internal aqueous phase in HIPE occupies more than 74 % of the total volume, which leads to highly porous and open-cell morphologies. In this paper a method of preparing polyHIPE foams by using reversible addition-fragmentation chain transfer (RAFT) polymerisation has been investigated. Polystyrene-co-polymethyl methacrylate (PS-co-PMMA) has been studied and by using a variety of characterisation methods, it was possible to compare the polyHIPEs prepared by the conventional free radical polymerisation (FRP) to those by RAFT polymerisation. Scanning electron microscopy images have confirmed the presence of a cellular polyHIPE structure. PS-co-PMMA polyHIPEs made by RAFT have significantly narrower molecular weight distribution with values for the polydispersity index (PDI) for PS-co-PMMA between 1.46 and 2.08 compared to 4.68 observed by FRP. The effects of different concentrations of the RAFT agent on structure, glass transition temperature (T _g) and PDI of PS-co-PMMA polyHIPE foams are presented.     

Synthesis and characterisation of PEG-peptide surfaces for proteolytic enzyme detection

Peptide surfaces were obtained by the covalent immobilisation of fluorescently labelled pentapeptides carboxyfluorescein–glycine–arginine–methionine–leucine–glycine, either directly or through a poly(ethylene glycol) (PEG) linker on modified silicon wafers. Each step during the preparation of the peptide surfaces was confirmed by several surface characterisation techniques. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy were used to determine the surface composition, the wafers philicity was measured by contact angle and atomic force microscopy was used to investigate the surface morphology. Exposure of the peptide surfaces to trypsin resulted in the release of a fluorescently labelled peptide product, which allowed the kinetics of the enzymatic reaction to be followed with the aid of fluorescence spectroscopy. The electrospray ionisation mass spectrometry analysis of the post-digestion solution confirmed that the pentapeptides attached to the solid support undergo specific trypsin hydrolysis at the C-terminus of the arginine residues. Detailed surface analyses before and after the enzyme action was performed using ToF-SIMS. Because of the limited accessibility of the short peptide directly attached to the surface, a quantitative yield of enzymatic hydrolysis was observed only in case when the peptide was bound through the PEG linker. The insertion of the PEG linker increased the number of immobilised peptides and the rate of enzymatic digestion which consequently improved the quality of the enzyme assays. The described approach may be used for different peptide sequences designed for other proteases.

Synthesis and structural characterisation of an yttrium-alkyl-alkylidene

The first structurally authenticated yttrium-alkyl-alkylidene is reported; structural, spectroscopic, and theoretical analyses show that whilst the yttrium-alkylidene bond is short, it possesses a bond order less than one and is comparable to the Y-C(alkyl) single bond within the same molecule.     

Synthesis and characterisation of aromatic ethynyl-bridged ferrocenes

A series of aromatic ethynyl-bridged ferrocenes with the general formula Fc-CC-R-CC-Fc (Fc=ferrocenyl, R=C₆H₂(-p-CH₃)₂ (1), C₆H₄-p-C₆H₄ (2), C₅H₃N (3), 9,10-C₁₄H₈ (4), C₄H₂S (5), (C₄H₂S)₂ (6) and (C₄H₂S)₃ (7)) has been synthesised by the reaction of ethynyl ferrocene with the appropriate dibromo-arenes. The new complexes have been characterised by spectroscopic techniques. The structures of 3 and 7 were determined via X-ray crystallography, and both show the trans-trans configuration of the two ethynyl ferrocene groups with respect to the central R group. The electronic properties of the compounds have been studied via optical spectroscopy and cyclic voltammetry.     

Synthesis and characterisation of small ZnS particles

Small ZnS particles, prepared at room temperature in an alcoholic medium using a zinc salt and thioacetamide as sulphur source, have been characterised using a suite of techniques which includes XRD, TEM and Zn K-edge EXAFS. The investigation suggests that aggregates of small sphalerite particles (cubic lattice), with average size of 3.5 nm and well-defined morphology are obtained and the particle size appears not to change with increase in the reaction time from 2 to 24 h. Zn K-edge EXAFS experiments were performed at 10 K, in order to reduce thermal disorder and the refinement of the EXAFS data resulted in very small second shell coordination numbers with respect to the bulk samples. The result is in good agreement with SEM and XRD data about the presence of nanosized particles, having a large number of surface atoms with low second shell coordination number.     

Synthesis and characterisation of the compound CoSbS

In the search for new intermetallic materials with high thermoelectric performances, the Co–Sb–S ternary system has been explored and polycrystalline CoSbS samples have been prepared by a vapour phase technique starting from the pure elements. The crystal cell of CoSbS belongs to the Pbca space group and shows an orthorhombic structural arrangement with the following lattice parameters: a = 5.8341(2) Å; b = 5.9477(2) Å, and c = 11.6540(4) Å. The structure belongs to the pyrite–marcasite family, as Co forms tilted corner- and edge-sharing octahedra with three Sb and three S atoms. Scanning electronic microscopy (SEM), electron-probe microanalysis (EPMA) and X-ray powder diffraction were used to investigate the microstructure and to carry out the structural analysis; the crystal structure was refined by the Rietveld method using the DBWS-9807 program. The thermal stability of CoSbS was investigated referring to the ternary Co–S–Sb phase diagram and by differential thermal analysis (DTA) measurements. Thermoelectric power measurements at room temperature were also performed by a home-made instrument.     

Synthesis and characterisation of nanofibrillar cellulose aerogels

We prepared from cellulose fibres monolithic aero- and cryogels. Cellulose is dissolved in hydrated calciumthiocyanate melt, gelled, aged and dried by several methods. The density of cellulose aerogels produced by supercritical drying is in the range between 10 and 60 kg/m³ with a surface area of 200–220 m²/g. The cellulose cryogels produced by freeze drying exhibit a maximum surface area of 160 m²/g. Sputtered cellulose aero- and cryogels are examined with a scanning electron microscope. The results are discussed with respect to the literature and simple mathematical models.