Synthesis,crystal structure and magnetic properties of the helical oxalate-bridged copper(II) chain {[(CH3)4N]2[Cu(C2O4)2] · H2O}n

The preparation, crystal structure and magnetic properties of a new oxalate-containing copper(II) chain of formula {[(CH₃)₄N]₂[Cu(C₂O₄)₂] · H₂O}_n (1) [(CH₃)₄N⁺ = tetramethylammonium cation] are reported. The structure of 1 consists of anionic oxalate-bridged copper(II) chains, tetramethylammoniun cations and crystallization water molecules. Each copper(II) ion in 1 is surrounded by three oxalate ligands, one being bidentate and the other two exhibiting bis-bidenate coordination modes. Although all the tris-chelated copper(II) units from a given chain exhibit the same helicity, adjacent chains have opposite helicities and then an achiral structure results. Variable-temperature magnetic susceptibility measurements of 1 show the occurrence of a weak ferromagnetic interaction through the oxalate bridge [J = +1.14(1) cm⁻¹, the Hamiltonian being defined as H = –J ∑_nmS_i · S_j]. This value is analyzed and discussed in the light of available magneto-structural data for oxalate-bridged copper(II) complexes with the same out-of-plane exchange pathway.     

The determination and characterisation of 2-naphthyloxycarbonyl chloride derivatised biogenic amines in pet foods

The need to monitor biogenic amines levels is essential for many areas of the food industry for two main reasons: the caustic nature and potential toxicity of these amines, and the potential to use amine levels as markers for freshness and quality in foodstuffs. Optimised analysis conditions used for the determination of biogenic amines derivatised with 2-napthyloxycarbonyl chloride has been applied to different pet food samples to assess the effectiveness of this method for complex sample matrices. Further to this, the use of high-resolution mass spectrometry has enabled the previously unconfirmed derivatised form of seven biogenic amines to be established. The derivatised forms identified include as mono substituted (tryptamine and histamine), bisubstituted (putrescine, cadaverine and tyramine), trisubstituted (spermidine) and tetrasubstituted (spermine). The methodology of biogenic amine determination was performed successfully to a range of pet food products highlighting the applicability to a variety of complex sample matrices.     

A four coordinate parent imide via a titanium nitridyl

Treatment of d(1) [(nacnac)TiCl(Ntol(2))] with NaN(3) results in NaCl formation and N(2) ejection to yield the first four coordinate, parent imide [(nacnac)Ti=NH(Ntol(2))] (nacnac(-)=[ArNC(CH(3))](2)CH, Ar = 2,6-iPr(2)C(6)H(3), tol = 4-CH(3)C(6)H(4)).     

Silver atom and strand numbers in fluorescent and dark Ag:DNAs

We use tandem HPLC-mass spectrometry with in-line spectroscopy to identify silver atom numbers, N(Ag), of 10 to 21 in visible- to infrared-emitting Ag:DNA complexes stabilized by oligonucleotide monomers and dimers. Qualitatively different absorbance spectra from bare, same-N(Ag) silver clusters point to silver-base interactions as the origin for the color of Ag:DNAs.     

Dimerization and anion binding of a fluorescent phospholipid analogue

A diarylacetylene fluorophore featuring spatially separated urea and phosphocholine (PC) groups forms a macrocyclic "head-to-tail" dimer stabilized by NH(urea)···OP(PC) hydrogen bonds. At concentrations above ～2 × 10(-5) M in CH(2)Cl(2), the emission intensity of the dimer is quenched by HCO(3)(-) and H(2)PO(4)(-) but not by Cl(-) and NO(3)(-). Under more dilute conditions, all four anions are bound unselectively with association constants on the order of 10(5) M(-1).     

Synthesis and characterization of Er3SmQ6 (Q=S, Se) and Er1.12Sm0.88Se3

The interlanthanide compounds Er₃SmS₆, Er₃SmSe₆, and Er_1.12Sm_0.88Se₃ have been synthesized from stoichiometric reactions of the elements in a KI salt flux at 1273, 1173, and 1123 K, respectively. Er₃SmS₆ and Er₃SmSe₆, which are isostructural and ordered, crystallize in space group P2₁/m in the ScEr₃S₆ structure type whereas Er_1.12Sm_0.88Se₃, in which the Er and Sm atoms are disordered, crystallizes in space group Pnma in the U₂S₃ structure type. Er₃SmS₆ is a paramagnet with a μ_eff=11.25(1) μ_B/mol. From optical measurements a direct band gap of 2.0 eV for light perpendicular to the (100) crystal face of Er₃SmSe₆ is derived whereas for isostructural Er₃SmS₆ an optical transition at 2.2-2.4 eV and a broad absorption peak at lower energies are observed.     

Stabilization of the structure and unctions of a photosystem i submembrane fraction by immobilization in an albumin-glutaraldehyde matrix

The effect of immobilization in an albumin-glutaraldehyde crosslinked matrix on the structure and activity of a photosystem I submembrane fraction has been studied. The photosynthetic activity recovered after immobilization was between 35 and 45% of the oxygen-uptake rates of the native material. Resulting oxygen uptake activities found in immobilized photosystem I preparations with methylviologen as acceptor were as high as 270 μmol O₂ (mg Chl h)^-1, An enhancement of photosystem I electron transfer, which is produced by incubation of thylakoid membranes at temperatures above 30 °C, was detected in native submembrane fractions, but not in the immobilized preparations. It is suggested that the increased activity at high temperature results from conformational modifications not allowed in the immobilization matrix. The insensitivity of immobilized photosystem I particles to prolonged storage at 4°C and to strong light exposure, as well as their high electron-transfer rates, demonstrates that the immobilization procedure used can be successfully applied to submembrane fractions.     

Synthesis and properties of miscible epoxy/acrylic interpenetrating polymer networks

Three series of epoxy/acrylic interpenetrating polymer networks were prepared by the simultaneous polymerization of diglycidyl ether of bisphenol A, crosslinked with an aliphatic diamine, diglycidyl ether of bisphenol A dimethacrylate, bisphenol A dimethacrylate, and diethoxy bisphenol A dimethacrylate. Under the conditions provided it is believed that the two networks form simultaneously but independently. Differential scanning calorimetry and dielectric measurements indicate that these polymer networks are miscible because they exhibit a single, sharp glass transition temperature, the values of which, however, are lower than predicted by the law of mixture. This decrease may be due in part to the dilution of one network by the other and to the resulting breakage of intramolecular interactions. It is also due, in part or in whole, to the presence of solvent and/or monomer impurities that act as plasticizers.     

Synthesis and phase characterization of a double-tailed pyrrole-containing surfactant: a novel tecton for the production of functional nanostructured materials

A double-tailed polymerizable (pyrrolylalkyl) ammonium amphiphile has been synthesized, and its interfacial properties and aqueous phase behavior have been studied by polarized optical microscopy and X-ray diffraction. The Krafft temperature is about 27 degrees C, and the critical micelle concentration at 40 degrees C is about 1 mM, as obtained from surface tension measurements, potentiometry, and isothermal titration calorimetry. The lyotropic behavior of the surfactant is found to be of a complex nature. At concentrations higher than the micellar (L1) region, two mesophases have been identified: a second isotropic (L2) phase, which is probably micellar but not fully miscible with water, and a lamellar (L(alpha)) phase, showing interesting alignment properties. Small-angle X-ray scattering analysis of the mesophases has been evaluated in terms of a model of spherical micelles, which describes a mutual arrangement by a structure factor derived from a hard-sphere potential (Percus-Yevick, "PY", approach). Interest in the comprehensive phase behavior of the polymerizable surfactant is based on the desire to integrate the system into a composite material to obtain potentially conducting self-assembled hybrid mesostructures.     

A family of strong low-molecular-weight organogelators based on aminoacid derivatives

A new family of potent aminoacid-type organogelators obtained via an easy and unexpensive way is described. We demonstrated that structural variations onto the side chains of the aminoacid derivatives allowed modulations of the gelation properties. The organogelators bearing a benzyl or an isopropyl group (compounds 1e, 2a, and 2c) are able to provide gelation of apolar solvents at very low concentration (0.2 wt %) and to form thermostable gels.