Characterization of tetra,dodeca and tetradeca MoV polyoxometalate wheels structured by etidronate ligands

The reactivity of the [Mo^V₂O₄]²⁺ dinuclear unit with the [O₃P(C(CH₃)(OH))PO₃]^4? etidronate ligand has been investigated. Three complexes have been isolated and characterized by IR spectroscopy, elemental analysis and single crystal X-Ray diffraction studies. Structural determination of the tetranuclear compound (CN₃H₆)₆[(Mo^V₂O₄)₂(O₃P(C(CH₃)O)PO₃)₂]·12H₂O (1) revealed that the hydroxo group of the etidronate ligand can be deprotonated in presence of Mo^V even in acidic media. It follows that its coordination mode thus differs from that of the methylenediphosphonate ligand [O₃P(CH₂)PO3]4?, which reactivity with Mo^V has been previously widely studied. In contrast, no such deprotonation of the hydroxo group is observed in the (NH₄)₁₈[(Mo^V₂O₄)₆(OH)₆(O₃P(C(CH₃)(OH))PO₃)₆]·35H₂O complex 2. This species contains a dodecanuclear core analogous to the one previously found in the [(Mo^V₂O₄)₆(OH)₆(O₃PCH₂PO₃)₆]^18? methylenediphosphonato polyanion. In 2, six interconnected {(Mo^V₂O₄)(O₃P(C(CH₃)(OH))PO₃)} units form a cyclohexane-like ring in a chair conformation. In the (CN₃H₆)₁₈Na₃[(Mo^V₂O₄)₇(O₃P(C(CH₃)(OH))PO₃)₇(CH₃COO)₇]·5CH₃COONa 52H₂O compound 3, seven {(Mo^V₂O₄)(O₃P(C(CH₃)(OH))PO₃)(CH₃COO)} units are connected, forming an almost planar tetradecanuclear wheel. This compound represents the largest homometallic Mo^V polyoxometalate cyclic system reported to date. Finally, ³¹P NMR studies revealed that only complex 1 is stable in aqueous solution.     

Effect of a new hydrophobically modified polyampholyte on the formation of inverse microemulsions and the preparation of gold nanoparticles

A new regular polyampholyte, namely poly-(N,N-dially-N,N-dimethylammonium-alt-N-octyl-maleamic carboxylate), was synthesized by alternating free radical copolymerization. The influence of the added polymer on the range of the inverse micellar region (L(2) phase) of a SDS-based system was investigated. The phase behavior as well as conductivity measurements indicate that the polymer, which forms hydrophobic microdomains, is located more in the water core of the microemulsion droplets rather than at the interface of the surfactant film. The polyampholyte proved to be an efficient reducing and stabilizing agent for the formation of gold colloids. The process of nanoparticle formation was investigated in the absence of any other reducing agent, in water as well as in the microemulsion template phase. In both cases, nanoscalic gold particles can be synthesized, while the adsorption of the polymer on the particle surface prevents their aggregation due to electrosteric stabilization.     

Validation of UV spectrophotometric and nonaqueous titration methods for the determination of carvedilol in pharmaceutical formulations

Ultraviolet (UV) spectrophotometric and nonaqueous volumetric methods are described for the determination of carvedilol in pharmaceutical formulations. Linearity, precision, and accuracy were evaluated according to the validation guidelines of the International Conference on Harmonization and the United States Pharmacopeia for both methods. The UV spectrophotometric procedure was performed in ethanol at 244 nm. Good linearity was obtained between 2 and 7 microg/mL with a correlation coefficient of 0.9999. The intra- and interday precision values were <2% for all samples analyzed. The accuracy, determined from recovery studies, was between 97.5 and 102.2%. The other procedure was based on the volumetric quantitation of carvedilol in a nonaqueous medium with 0.01 M perchloric acid and 1% violet crystal as the indicator. The validation of the volumetric method yielded good results that included linearity (r of > 0.999), precision (relative standard deviations of <2% for intra- and interday precision), and accuracy (96.4-102.4%). The methods were applied to tablets and compounded capsules. Statistical analysis by analysis of variance showed no significant difference between the results obtained by the proposed methods.     

A liquid chromatography‐atmospheric pressure photoionization tandem mass spectrometric (LC‐APPI‐MS/MS) method for the determination of triterpenoids in medicinal plant extracts

An analytical method using liquid chromatography‐atmospheric pressure photoionization tandem mass spectrometry with toluene as a dopant was developed for the determination of triterpenes in medicinal plant extracts. The 12 compounds determined have been shown to exhibit biological activity, such as gastroprotective, hepatoprotective, anti‐inflammatory, antiviral and anti‐tumor effects. The parameters of the atmospheric pressure photoionization interface were optimized to obtain the highest possible sensitivity for all of the compounds. The limits of detection and quantification ranged from 0.4 to 157.9 µg l^?1 and 1.3 to 526.4 µg l^?1, respectively. The method was validated and applied to extracts of five medicinal plants species (Mansoa alliacea (Lam.) A.H.Gentry, Bauhinia variegata var variegata, Bauhinia variegata var alboflava, Cecropia obtuse Trécul and Cecropia palmate Willd) from the Amazonian region. The concentrations of the six triterpenes quantified in the samples ranged from 0.424 mg kg^?1 for ursolic acid to 371.96 mg kg^?1 for β‐amyrin, which were quantified by using the standard addition method (n = 3). Copyright © 2016 John Wiley & Sons, Ltd.     

Structure and properties of dinuclear manganese(III) complexes with pentaanionic pentadentate ligands including alkoxo, amido, and phenoxo donors

Doubly bridged mu-alkoxo-mu-X (X = pyrazolato or acetato) dinuclear MnIII complexes of 2-hydroxy-N-{2-hydroxy-3-[(2-hydroxybenzoyl)amino]propyl}benzamide) (H5L1) and 2-hydroxy-N-{2-hydroxy-4-[(2-hydroxybenzoyl)amino]butyl}benzamide (H5L2), [Mn2(L)(pz)(MeOH)4].xMeOH (1, L = L1, x = 0.5; 2, L = L2, x = 0; Hpz = pyrazole) and [Mn2(L1)(OAc)(MeOH)4] (3), have been prepared, and their structure and magnetic properties have been studied. The X-ray diffraction analysis of 1 (C24.5H34Mn2N4O9.5, triclinic, P, a = 12.2050(7) A, b = 12.7360(8) A, c = 19.2780(10) A, alpha = 99.735(5) degrees , beta = 96.003(4) degrees , gamma = 101.221(5) degrees , V = 2867.6(3) A3, Z = 4), 2 (C25H34Mn2N4O9, triclinic, P, a = 9.4560(5) A, b = 11.0112(5) A, c = 13.8831(6) A, alpha = 90.821(4) degrees , beta = 92.597(4) degrees , gamma = 93.403(4) degrees , V = 1441.29(12) A3, Z = 2), and 3 (C23H32Mn2N2O11, triclinic, P, a = 10.511(5) A, b = 11.713(5) A, c = 13.135(5) A, alpha = 64.401(5) degrees , beta = 74.000(5) degrees , gamma = 66.774(5) degrees , V = 1329.3(10) A3, Z = 2) revealed that all complexes consist of dinuclear units which are further extended into 1D (1 and 3) and 2D (2) supramolecular networks via hydrogen-bonding interactions. Magnetic susceptibility data evidence antiferromagnetic interactions for all three complexes: J = -3.6 cm-1, D approximately 0 cm-1, g = 1.93 (1); J = -2.7 cm-1, D = 0.8 cm-1, g = 1.93 (2); J = -4.9 cm-1, D = 3.8 cm-1, g = 1.95 (3).     

Synthesis of 3′-deoxy-3′-iminodiacetic acid and 3′-deoxy-3′-aminodiethanol thymidine analogues and NMR study of their complexation with boronic acids

The iminodiacetic acid and aminodiethanol moieties are known for their ability to generate with boronic acids bicyclic structures having a strong intramolecular NB coordination. We describe here the convergent synthesis of 3′-deoxy-3′-iminodiacetic acid and 3′-deoxy-3′-aminodiethanol thymidine analogues. The abilities of these compounds to form boronate complexes with aliphatic or aromatic boronic acids were established by 1D and 2D ¹H and ¹³C NMR. Moreover, conformational analysis of the newly synthesized compounds revealed a marked preference for an N-type sugar puckering.     

The role of temperature in the synthesis of hybrid inorganic-organic materials: the example of cobalt succinates

Five different cobalt succinate materials synthesized from an identical starting mixture using temperature as the only independent variable show increasing condensation and density at higher synthesis temperatures.     

Direct synthesis and aqueous solution properties of Y-shaped, stimulus-responsive block copolymer surfactants

We report the direct synthesis of a wide range of well-defined, Y-shaped stimulus-responsive block copolymers under mild conditions; the aqueous solution behaviour of these new polymeric surfactants has been investigated.