Crystal Structure of 5ʹ-Oxospiro-(fluorene-9,4ʹ-imidazolidine)-2ʹ-thione and Biological Activity of Its Derivatives

Russian Journal of General Chemistry - The presented study is devoted to the structural and biological properties of four derivatives of fluorenylspirohydantoin based on experimental data. The...     

2-Methylthio-imidazolins: a rare case of different tautomeric forms in solid state and in solution

Structural Chemistry - The synthesis and structure elucidation of two new compounds, 2-(methylthio)-1,3-diazaspiro[4.4]non-2-ene-4-one (1) and 2-(methylthio)-1,3-diazaspiro[4.4]non-2-ene-4-thione...     

Isolating fluorinated carbocations

Using carboranes as counterions, fluorinated benzyl-type carbocations such as (p-FC(6)H(4))(2)CF(+), (p-FC(6)H(4))(CH(3))CF(+) and fluorinated trityl ions are readily isolated for X-ray and IR structural characterization.     

Emulsifier‐Free Emulsion Copolymerization of Vinyl Acetate and 3‐Dimethyl(methacryloyloxyethyl)ammonium Propanesulfonate and Swelling Behavior of their Copolymer Matrices

Stable poly{(vinyl acetate)‐co‐[3‐dimethyl(methacryloyloxyethyl)ammonium propanesulfonate]} latexes with different compositions were synthesized by emulsifier‐free emulsion copolymerization. An unusual “overshooting” behavior of the copolymer tablets is explained based on the formation of specific clusters of oppositely oriented dipoles. The variation of their concentration with the zwitterionic monomer unit fraction, ionic strength and temperature is responsible for the differences in the swelling kinetics established. The results show that these parameters can be used to control swelling degree of copolymer matrices and their sustained drug delivery.

     

Influence of complexation on the composition of equilibrium phases in the system of Ce2(SO4)3-La2(SO4)3

The cocrystallization of Ce₂(SO₄)₃ and La₂(SO₄)₃ is studied in aqueous and H₂SO₄ (150 g/dm³) solutions at 25 °C and 64 °C. The effect of the formation of inner sphere sulfate complexes of the type LnSO ₄ ⁺ in determining the composition of the equilibrium phases is revealed.      

Mechanism of interaction between hydroxypropyl cellulose and water in aqueous solutions: Importance of polymer chain length

The utilization of hydroxypropyl cellulose (HPC) can be regarded as unexpected with regard to certain applications, such as being employed as a solubility enhancer for poorly soluble drugs and as a solubilizing agent for nano-suspensions and amorphous solid dispersions. However, the best results were obtained for low-molecular weight (M_w) HPC grades with a short-chain structure. Therefore, in this study, seven grades of HPC with different polymer chain lengths (M_w) are analyzed in various aqueous solutions by a combination of ¹H quantitative NMR spectroscopy, diffusion NMR spectroscopy, and water ligand observed via gradient spectroscopy; these investigations provide insights into the remarkable solubilizing property of HPC at the molecular and supramolecular levels. Furthermore, the hydration and the water residence time are found to be strongly dependent on the polymer chain length of HPC. The quantitative results obtained herein indicate that HPCs with shorter chain lengths retain smaller amounts of water around their hydrated molecules, as compared to their counterparts with longer chain lengths.     

Mechanochemical synthesis of some europium diketonates

Results on the influence of mechanoactivation (3–30 min) in a planetary ball mill on the composition, crystal structure, IR spectra and morphology of EuCl₃·6H₂O, dibenzoylmethane (HDBM) and mixtures of EuCl₃·6H₂O — HDBM and EuCl₃·6H₂O — HDBM — 1,10-phenathroline (phen) are presented. Mechanoactivation leads to a decrease of interplanar distances of the EuCl₃·6H₂O and HDBM and partial synthesis of Eu(DBM)₃ and Eu(DBM)₃·phen in the respective mixtures. The fluorescence properties of the products of activation (excitation and emission spectra, lifetime of the excited states) are similar to those of the complexes produced by the conventional “wet” methods, but the strongest excitation of the mechanochemically produced solid state samples is achieved at higher wavelength. Crystals of different forms (prismatic, needle-, long-length-leaf- and rod-like) are formed by mechanoactivation of the mentioned mixtures.     

Use of cation exchange chromatography for human C-peptide isotope dilution - mass spectrometric assay

An application of ion exchange chromatography for C-peptide analysis is described here. At the stage of C-peptide isolation, a strong cation exchanger (SP HP or MonoS) was used to purify the analyte from ballast proteins and peptides. The conditions of ion-exchange chromatographic separations were optimized using theoretical modeling of the net surface electric charge of the peptide as a function of pH. The purified and concentrated sample was further subjected to LC-MS/MS. In order to improve the reliability of analysis, two fragment ions were monitored simultaneously both for native C-peptide and internal standard, isotopically labeled C-peptides analogues (fragments with m/z of 927.7 and 147.2). Using ion-exchange chromatography, it became possible to process larger sample volumes, important for testing patients with very low C peptide levels, compared to currently used solid phase extraction methods.     

Polymer compatibility in two dimensions. Modeling of phase behavior of mixed polymethacrylate Langmuir films

We analyze the possibility of polymer blends undergoing phase separation in two dimensions. To this end, we investigate a model system consisting of water-supported Langmuir monolayers, obtained from binary polyalkyl-methacrylate mixtures (PXMA, where X stands for any of the type of ester side groups used: M, methyl-; E, ethyl-; B, butyl-; H, hexyl-; O, octyl-; L, lauryl-methacrylate), by means of self consistent field (SCF) calculations. In particular, we address the conditions which determine demixing and phase separation in the two-dimensional system, showing that a sufficient chain length mismatch in the ester side group moieties is able to drive the polymer demixing. When the difference in length of the alkyl chain of the ester moieties on the two types of polymers is progressively reduced, from 11 carbon atoms (PMMA/PLMA) to 4 carbons only (POMA/PLMA), the demixing tendency is also reduced. The polymer/subphase interactions affect more the distribution of the polymer coils in the POMA/PLMA blend monolayer. Mixing of the two polymers is observed, but also a partial layering along the vertical direction. We also add, to a PMMA/PLMA blended monolayer, a third component, namely, a symmetrical diblock copolymer of the type PLMA-b-PMMA. We observe adsorption of the diblock copolymer exclusively at the contact line between the two homopolymer domains, and a concomitant lowering of the line tension. The line tension varies with the chemical potential of the diblock copolymer according to Gibbs' law, which demonstrates that PLMA-b-PMMA can act as a "lineactant" (the equivalent of a surfactant in two-dimensional systems) in the binary demixed PMMA/PLMA Langmuir monolayer.     

Spectroscopic elucidation of the interaction of native cyclodextrins and their acetylated derivatives with asymmetric monomethyne cyanine dye

Five novel complexes of asymmetric monomethyne cyanine dye (1), with α-, β-, γ-cyclodextrins and the corresponding functionalized derivatives, namely acetyl-β-(Ac-β-CD) and acetyl-γ-(Ac-γ-CD) cyclodextrins were studied by means of UV–VIS, linear-polarized infrared and fluorescence spectroscopy, as well as scanning electron microscopy, powder X-ray diffraction, and thermal methods both in solution and in solid-state. Computational chemistry methods were employed with the purpose of elucidating the electronic structure and vibrational properties of the organic dye.