Kinetic study of triphenylphosphine addition to para‐benzoquinone

Kinetics of the addition reaction of triphenylphosphine to para‐benzoquinone in 1,2‐dichloroethane as solvent was studied. Initial rate method was used to determine the order of the reaction with respect to the reactants. Pseudo‐first‐order method was also used to calculate the rate constant. This reaction was monitored by UV‐vis spectrophotometry at 520 nm by variable time method. On the basis of the obtained results, the Arrhenius equation of this reaction was obtained: The activation parameters, E_a, ΔH^#, ΔG^#, and ΔS^# at 300 K were 5.701, 6.294, 19.958 kcal mol^?1 and ?45.853 cal mol^?1 K^?1, respectively. This reaction is first and second order with respect to triphenylphosphine and para‐benzoquinone, respectively. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36:472–479, 2004     

Chlorhexidine/losartan ionic pair binding and its nanoprecipitation: physico-chemical characterisation and antimicrobial activity

Chlorhexidine is a widely used, di-cationic, broad-spectrum antimicrobial agent and losartan is a well-known, anionic-specific antagonist of AT1 renin–angiotensin receptor that acts as an anti-hypertensive agent. The combination of these molecules gives a chlorhexidine di-losartanate (ClxLos₂) hydrophobic ion pair that spontaneously aggregates into nanoparticles (NPs). This work investigated the formation of ClxLos₂ NPs using the analysis of the solid state by fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy and in aqueous environment by calorimetric, zeta potential and dynamic light scattering titrations. Furthermore, to demonstrate the potential antimicrobial activity of ClxLos₂, in vitro antibacterial tests were conducted against Staphylococcus aureus (ATCC 27664), Streptococcus viridans (ATCC 11563) and Enterococcus faecalis (ATCC 14508). Based on these studies, it is proposed that ClxLos₂ could be used for controlled drug release based on ionic dissociation during dilution, thereby avoiding the use of any solid matrix.     

Complexes of Tin(IV) Tetrachloride with 3-Formylpyridine Semicarbazone and Thiosemicarbazones

The reaction of tin(IV) tetrachloride with 3-formylpyridine semicarbazone and different 3-formylpyridine thiosemicarbazones produces [Sn(HL)CL 3 ][SnCl 5 ] where HL stands for the neutral ligand. The tin(IV) complexes were characterized using a variety of spectroscopic techniques. Coordination through the pyridine nitrogen occurs in all cases. Solvation studies in DMSO indicated that dissociation of the ligands and their complete replacement by solvent molecules occurs.     

Synergistic Strategies in Aminocatalysis

Synergistic catalysis offers the unique possibility of simultaneous activation of both the nucleophile and the electrophile in a reaction. A requirement for this strategy is the stability of the active species towards the reaction conditions and the two concerted catalytic cycles. Since the beginning of the century, aminocatalysis has been established as a platform for the stereoselective activation of carbonyl compounds through HOMO-raising or LUMO-lowering. The burgeoning era of aminocatalysis has been driven by a deep understanding of these activation and stereoinduction modes, thanks to the introduction of versatile and privileged chiral amines. The aim of this review is to cover recent developments in synergistic strategies involving aminocatalysis in combination with organo-, metal-, photo-, and electro-catalysis, focusing on the evolution of privileged aminocatalysts architectures.     

Surface Josephson plasma waves in layered superconductors

We predict the existence of surface waves in layered superconductors in the THz frequency range, below the Josephson plasma frequency omega J. This wave propagates along the vacuum-superconductor interface and dampens in both transverse directions out of the surface (i.e., towards the superconductor and towards the vacuum). This is the first prediction of propagating surface waves in any superconductor. These predicted surface Josephson plasma waves are important for different phenomena, including the complete suppression of the specular reflection from a sample (Wood's anomalies) and a huge enhancement of the wave absorption (which can be used as a THz detector).     

Controlling the motion of magnetic flux quanta

We study the transport of vortices in superconductors with triangular arrays of boomerang- or V-shaped asymmetric pinning wells, when applying an alternating electrical current. The asymmetry of the pinning landscape induces a very efficient "diode" effect, that allows the sculpting at will of the magnetic field profile inside the sample. We present the first quantitative study of magnetic "lensing" of fluxons inside superconductors. Our proposed vortex lens provides a near threefold increase of the vortex density at its "focus" regions. The main numerical features have been derived analytically.