Isolation and single crystal study of [Nb2(μ-OMe)2(OiPr)8]. Can alcohol interchange provide the homoleptic niobium isopropoxide?

Niobium isopropoxide, Nb(OⁱPr)₅, is an attractive precursor of simple and complex niobium oxides in sol-gel technology. This compound cannot, unfortunately, be obtained by alcohol interchange starting from linear chain homologues such as Nb(OMe)₅ or Nb(OEt)₅. The equilibrium in the latter reaction favours formation of mixed-ligand complexes, [Nb₂(OR)₂(OⁱPr)₈], R = Me, Et. In particular, [Nb₂(OMe)₂(OPrⁱ)₈] (1) has been isolated in high yield from repeated treatment of Nb₂(OMe)₁₀ with excess of isopropanol. The X-ray single crystal study reveals a dinuclear structure containing a pair of edge-sharing octahedra with methoxide ligands in the bridging position. Infrared (IR) and mass spectroscopy (MS) studies confirmed the incomplete ligand substitution. The ¹H-NMR spectra suggest equilibrium between different molecular forms in solution. Solvothermal interaction of 1 with La chips in toluene/isopropanol media results in formation of a mixture of LaNb₂(OⁱPr)₁₃ and La₂Nb₄(μ₄−O)₄(OH)₂(μ−OⁱPr)₈(OⁱPr)₈ (2). Electronic Supplementary Material The online version of this article (doi: ) contains supplementary material, which is available to authorised users.     

Thermal and morphological characterization of highly porous nanocomposites for possible application in potassium controlled release

The use of fertilizer and water availability are essential factors limiting the agricultural production. The controlled release technology is very promising because it allows the maintenance of fertilizer concentrations within an ideal range avoiding inefficiency and toxicity problems, minimizing the environmental impacts and improving their efficiency. In this context, the nanostructured hydrogels appear as a possible carrier vehicle for these controlled release systems due to their inherent properties, such as biodegradability, low toxicity, and cost, rapid absorption and desorption controlled capacity of water and solutes. In this work, we performed the synthesis of nanostructured hydrogels based on poly(methacrylic acid) (PMAA)/Cloisite-Na⁺ via free radical polymerization. SEM images indicated a similarity in the basic structure of all nanocomposites. The porous diameter of the hydrogels increased with increasing of nanoclay content. EDS analysis showed the ions belonging to nanoclay present in the nanocomposites, confirming the formation of true nanocomposites. TG–DTG and DSC techniques confirmed an improvement in the thermal stability of nanocomposites caused by the addition of nanoclay. For instance, the degradation initial temperature of the hydrogel was increased from 198.5 to 203.5 °C, and inversely, the degradation rate of the 2° thermal event was decreased from 0.694 to 0.472% min °C^?1, when the nanoclay was increased from 0 to 20 mass/%. Moreover, the controlled release investigation showed an improvement in the release time and quantity of the fertilizer released with nanoclay content. This result is very required for this specific application.     

Study of thermoanalytical behavior of heavier lanthanides terephthalates in air atmosphere

Journal of Thermal Analysis and Calorimetry - Coordination compounds of heavier lanthanides with terephthalate ligand have been synthesized and characterized employing simultaneous thermogravimetry...     

Vegetable proteins and milk puddings

In recent years, interest in animal free foods has increased tremendously due to factors like BSE crisis, rise of nutritionally dependent illnesses, like diabetes type II, cardiovascular and digestive diseases, along with ethic orientations of denying animal intakes of any kind. The use of proteins from leguminous seeds as an alternative to the animal proteins in dairy desserts was studied. Lupin, pea and soya protein isolates were used in combination with κ-carrageenan, gellan and xanthan gum, in order to obtain a synergistic effect. Milk puddings were also produced for comparison. Texture studies suggested that mixed protein–polysaccharide systems, with vegetable proteins and κ-carrageenan or gellan gum, would be good systems to develop vegetable gelled desserts. Rheological oscillatory measurements were carried out to clarify the kinetics of gelation and characterise the microstructure of the best performing products. Results from time sweep tests showed that formulations with gellan gum present an industrial advantage over formulations with κ-carrageenan, since the maturation time for gellan gels is of the order of 5–10 h compared with 4–6 days in the case of κ-carrageenan. All the mixed gels presented the typical weak gel structure; therefore, it was possible to perform steady-state measurements, which allowed the observation of a shear-thinning behaviour for all gels.     

‘Higher-order’ azomethine ylides in the synthesis of functionalized pyrroles and 5-oxo-5H-pyrrolizines

Azafulvenium methides generated by the thermal extrusion of SO₂ from 1-methyl- and 1,1-dimethyl-1H,3H-pyrrolo[1,2-c]thiazole-2,2-dioxides undergo [1,8]H sigmatropic shifts to give vinylpyrroles. Flash vacuum pyrolysis of the C-vinylpyrroles affords 5-oxo-5H-pyrrolizines or C-allyl-1H-pyrroles.     

Trace elements determination by energy dispersive X-ray fluorescence (EDXRF) in human placenta and membrane: a comparative study

This work is an application of energy dispersive X-ray fluorescence (EDXRF) as an analytical technique for trace elemental determination in human membrane and placenta and elemental concentrations correlations in both tissues. Whole samples were collected during the delivery from healthy mothers and full-term pregnancies. The age of the mother was between 25 and 40 years old, and the weight of the infants ranged from 2.56 to 4.05 kg. Samples were lyophilised and analysed without any chemical treatment. No significant differences in elemental content of placenta and membrane samples were observed except for Ca. Very low levels of Se, As and Pb were observed in all the analysed samples. Zn, considered as one of the key elements in newborn health, was not significantly different in the analysed samples, all of which originated from healthy mothers and healthy babies. The obtained values agree with the literature except for Ca, which is much higher in the studied samples.     

Recent Strategies and Applications for l-Asparaginase Confinement

l-asparaginase (ASNase, EC 3.5.1.1) is an aminohydrolase enzyme with important uses in the therapeutic/pharmaceutical and food industries. Its main applications are as an anticancer drug, mostly for acute lymphoblastic leukaemia (ALL) treatment, and in acrylamide reduction when starch-rich foods are cooked at temperatures above 100 °C. Its use as a biosensor for asparagine in both industries has also been reported. However, there are certain challenges associated with ASNase applications. Depending on the ASNase source, the major challenges of its pharmaceutical application are the hypersensitivity reactions that it causes in ALL patients and its short half-life and fast plasma clearance in the blood system by native proteases. In addition, ASNase is generally unstable and it is a thermolabile enzyme, which also hinders its application in the food sector. These drawbacks have been overcome by the ASNase confinement in different (nano)materials through distinct techniques, such as physical adsorption, covalent attachment and entrapment. Overall, this review describes the most recent strategies reported for ASNase confinement in numerous (nano)materials, highlighting its improved properties, especially specificity, half-life enhancement and thermal and operational stability improvement, allowing its reuse, increased proteolysis resistance and immunogenicity elimination. The most recent applications of confined ASNase in nanomaterials are reviewed for the first time, simultaneously providing prospects in the described fields of application.