Solvent bar microextraction combined with high‐performance liquid chromatography for preconcentration and determination of pramipexole in biological samples

A simple, rapid and sensitive analytical method for preconcentration and determination of pramipexole in different biological samples has been developed using solvent bar microextraction (SBME) combined with HPLC‐UV. The target drugs were extracted from 10 mL of basic aqueous sample solution into an organic extracting solvent located inside the pores of a polypropylene hollow fiber, then back‐extracted into an acidified aqueous solution in the lumen of the hollow fiber. In order to obtain high extraction efficiency, the effect of different variables on the extraction efficiency was studied simultaneously using an experimental design. The experimental parameters of SBME were optimized using a Box–Behnken design after a Plackett–Burman screening design. Under the optimized conditions, an enrichment factor up to 96 was achieved and the relative standard deviation of the method was 4.64% (n = 5). The linear range was 0.05–2000 µg/L with a correlation coefficient (r) of 0.987. Finally, the applicability of the proposed method was evaluated by extraction and determination of pramipexole in plasma and urine samples. The results indicated that SBME method has excellent clean‐up and high preconcentration factor and can serve as a simple and sensitive method for analysis of pramipexole in biological samples. Copyright © 2013 John Wiley & Sons, Ltd.     

Pyridylalkylamine ligands and their palladium complexes: structure and reactivity revisited by NMR

Pyridylmethylamines or pma are versatile platforms for different catalytic transformations. Five pma‐ligands and their respective Pd complexes have been studied by liquid state NMR. By comparing ¹H, ¹³C and ¹⁵N chemical shifts for each pma/pma–Pd couple, a general trend for the metallacycle atoms concerns variations of the electronic distribution at the pendant arm, especially at the nitrogen atom of the ligand. Moreover, the increase of the chemical shift of the pendant arm nitrogen atom from primary to tertiary amine is also related to the increase of crowding within the complex. This statement is in good agreement with X‐ray data collected for several complexes. Catalytic results for the Suzuki–Miyaura reaction involving the pma–Pd complexes showed within this series that a sterically crowded and electron‐rich ligand in the metallacycle was essential to reach the coupling product with a good selectivity. In this context, NMR study of chemical shifts of all active nuclei especially in the metallacycle could give a trend of reactivity in the studied family of pma–Pd complexes. Copyright © 2014 John Wiley & Sons, Ltd.     

Cubosome particles of a novel Guerbet branched chain glycolipid

Cubic liquid crystalline nanoparticles (cubosomes) of bicontinuous nature with internal networks of water channels have received great interests in nanomedicine applications, particularly as potential vehicle for loading and release of therapeutic agents. These nanoparticles have been most commonly produced using monoolein and phytantriol. In this study, we explore the use of a Guerbet branched chain glycolipid, namely 2-hexyl-decyl-β-D glucopyranoside (β-Glc?OC₁₀C₆), as a new and alternative material for cubosomes production. The fully hydrated glycolipid assumes a reverse bicontinuous cubic liquid crystal phase of an Ia3d space group with lattice parameter of ca. 74 Å, as confirmed using a small-angle X-ray scattering. Dynamic light scattering and a conventional transmission electron microscopy were used to investigate the average size and morphology of the cubosomes. The effectiveness of Poloxamer 407 (stabiliser typically used in other cubosome systems against aggregations and particle coalescence) in providing steric stabilisation of the glycolipid cubosomes was assessed through visual assessment.     

The Role of Hydrogen Bonding and Halogen Bonding in the Polymorphic Structures of 3,5-Dibromo-2,6-diaminopyridinium Bromide

Abstract  

An analysis is made of the supramolecular interactions in the two polymorphic structures of 3,5-dibromo-2,6-diaminopyridinium bromide, with particular emphasis on the roles of hydrogen and halogen bonding. Because of the extensive hydrogen bonding capabilities, hydrogen bonding interactions dominate in both phases. This causes a competition between C–Br···Br–C and C–Br···Br⁻ halogen bonding interactions, with the former dominating in the orthorhombic Pbca phase and the latter in the monoclinic P2₁/c phase. For Pbca phase a = 5.5197(11) ?, b = 15.040(3) ?, c = 23.2555(5) ?, and for P2₁/c phase a = 8.1143(19) ?, b = 14.226(3) ?, c = 8.9005(18) ?, β = 113.18(2)°.     

Ruthenium(II) 2,2′-bipyridine complexes incorporating substituted phenylazo-(2-(phenylthio))phenylmethine ancillary ligands. Synthesis,crystal structure,spectroscopic and redox properties

Abstract  

Five ruthenium complexes bearing phenylazo-(2-(phenylthio))phenylmethine ligands of the general type trans-[Ru^II(bpy)(L)(Cl)₂] (C1–C5) {L = YC₆H₄N=NC(COCH₃)=NC₆H₄(2-SC₆H₅), H (L1), Cl (L2), OCH₃ (L3), Br (L4), or NO₂ (L5)} have been synthesized. The crystal structure of trans-[Ru(bpy)(L1)(Cl)₂] (C1) is reported and shows no direct metal–S interaction. The complexes have been characterized through spectroscopic (IR, UV/vis and NMR) and electrochemical (CV) techniques. The electrochemical parameters (E _L(L)) of the azoimine ligands are reported.